complete implementation of long-polling for reserve status; remove support for multi-threaded exchange httpd

32 files changed, 255 insertions, 1121 deletions

diff --git a/src/exchange/Makefile.am b/src/exchange/Makefile.am
index 4c1f26dfc..1f53b0123 100644
--- a/src/exchange/Makefile.am
+++ b/src/exchange/Makefile.am
@@ -84,7 +84,6 @@ taler_exchange_httpd_SOURCES = \
   taler-exchange-httpd_deposits_get.c taler-exchange-httpd_deposits_get.h \
   taler-exchange-httpd_keys.c taler-exchange-httpd_keys.h \
   taler-exchange-httpd_link.c taler-exchange-httpd_link.h \
-  taler-exchange-httpd_loop.c taler-exchange-httpd_loop.h \
   taler-exchange-httpd_management.h \
   taler-exchange-httpd_management_auditors.c \
   taler-exchange-httpd_management_auditors_AP_disable.c \
@@ -122,7 +121,6 @@ taler_exchange_httpd_LDADD = \
   -lgnunetjson \
   -ljansson \
   -lz \
-  -lpthread \
   $(XLIB)
 
 # Testcases
@@ -130,8 +128,7 @@ taler_exchange_httpd_LDADD = \
 AM_TESTS_ENVIRONMENT=export TALER_PREFIX=$${TALER_PREFIX:-@libdir@};export PATH=$${TALER_PREFIX:-@prefix@}/bin:$$PATH;
 
 check_SCRIPTS = \
-  test_taler_exchange_httpd.sh \
-  test_taler_exchange_httpd_restart.sh
+  test_taler_exchange_httpd.sh
 if HAVE_EXPENSIVE_TESTS
 check_SCRIPTS += \
   test_taler_exchange_httpd_afl.sh
diff --git a/src/exchange/taler-exchange-aggregator.c b/src/exchange/taler-exchange-aggregator.c
index 5da0a8094..c82b66669 100644
--- a/src/exchange/taler-exchange-aggregator.c
+++ b/src/exchange/taler-exchange-aggregator.c
@@ -90,11 +90,6 @@ struct AggregationUnit
   const struct TALER_EXCHANGEDB_AccountInfo *wa;
 
   /**
-   * Database session for all of our transactions.
-   */
-  struct TALER_EXCHANGEDB_Session *session;
-
-  /**
    * Array of row_ids from the aggregation.
    */
   uint64_t additional_rows[TALER_EXCHANGEDB_MATCHING_DEPOSITS_LIMIT];
@@ -355,7 +350,6 @@ deposit_cb (void *cls,
   au->total_amount = *amount_with_fee;
   au->have_refund = GNUNET_NO;
   qs = db_plugin->select_refunds_by_coin (db_plugin->cls,
-                                          au->session,
                                           coin_pub,
                                           &au->merchant_pub,
                                           h_contract_terms,
@@ -444,7 +438,6 @@ deposit_cb (void *cls,
     enum GNUNET_DB_QueryStatus qs;
 
     qs = db_plugin->get_wire_fee (db_plugin->cls,
-                                  au->session,
                                   au->wa->method,
                                   au->execution_time,
                                   &start_date,
@@ -468,7 +461,6 @@ deposit_cb (void *cls,
               TALER_B2S (&au->wtid),
               TALER_amount2s (&au->wire_fee));
   qs = db_plugin->insert_aggregation_tracking (db_plugin->cls,
-                                               au->session,
                                                &au->wtid,
                                                row_id);
   if (qs <= 0)
@@ -480,7 +472,6 @@ deposit_cb (void *cls,
               "Aggregator marks deposit %llu as done\n",
               (unsigned long long) row_id);
   qs = db_plugin->mark_deposit_done (db_plugin->cls,
-                                     au->session,
                                      row_id);
   if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT != qs)
   {
@@ -535,7 +526,6 @@ aggregate_cb (void *cls,
   /* compute contribution of this coin (after fees) */
   au->have_refund = GNUNET_NO;
   qs = db_plugin->select_refunds_by_coin (db_plugin->cls,
-                                          au->session,
                                           coin_pub,
                                           &au->merchant_pub,
                                           h_contract_terms,
@@ -596,7 +586,6 @@ aggregate_cb (void *cls,
   au->additional_rows[au->rows_offset++] = row_id;
   /* insert into aggregation tracking table */
   qs = db_plugin->insert_aggregation_tracking (db_plugin->cls,
-                                               au->session,
                                                &au->wtid,
                                                row_id);
   if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT != qs)
@@ -605,7 +594,6 @@ aggregate_cb (void *cls,
     return qs;
   }
   qs = db_plugin->mark_deposit_done (db_plugin->cls,
-                                     au->session,
                                      row_id);
   if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT != qs)
   {
@@ -622,16 +610,14 @@ aggregate_cb (void *cls,
 /**
  * Perform a database commit. If it fails, print a warning.
  *
- * @param session session to perform the commit for.
  * @return status of commit
  */
 static enum GNUNET_DB_QueryStatus
-commit_or_warn (struct TALER_EXCHANGEDB_Session *session)
+commit_or_warn (void)
 {
   enum GNUNET_DB_QueryStatus qs;
 
-  qs = db_plugin->commit (db_plugin->cls,
-                          session);
+  qs = db_plugin->commit (db_plugin->cls);
   if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
     return qs;
   GNUNET_log ((GNUNET_DB_STATUS_SOFT_ERROR == qs)
@@ -652,24 +638,23 @@ static void
 run_aggregation (void *cls)
 {
   struct AggregationUnit au_active;
-  struct TALER_EXCHANGEDB_Session *session;
   enum GNUNET_DB_QueryStatus qs;
 
   (void) cls;
   task = NULL;
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
               "Checking for ready deposits to aggregate\n");
-  if (NULL == (session = db_plugin->get_session (db_plugin->cls)))
+  if (GNUNET_SYSERR ==
+      db_plugin->preflight (db_plugin->cls))
   {
     GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                "Failed to obtain database session!\n");
+                "Failed to obtain database connection!\n");
     global_ret = EXIT_FAILURE;
     GNUNET_SCHEDULER_shutdown ();
     return;
   }
   if (GNUNET_OK !=
-      db_plugin->start_deferred_wire_out (db_plugin->cls,
-                                          session))
+      db_plugin->start_deferred_wire_out (db_plugin->cls))
   {
     GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                 "Failed to start database transaction!\n");
@@ -680,16 +665,13 @@ run_aggregation (void *cls)
   memset (&au_active,
           0,
           sizeof (au_active));
-  au_active.session = session;
   qs = db_plugin->get_ready_deposit (db_plugin->cls,
-                                     session,
                                      &deposit_cb,
                                      &au_active);
   if (0 >= qs)
   {
     cleanup_au (&au_active);
-    db_plugin->rollback (db_plugin->cls,
-                         session);
+    db_plugin->rollback (db_plugin->cls);
     if (GNUNET_DB_STATUS_HARD_ERROR == qs)
     {
       GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
@@ -729,7 +711,6 @@ run_aggregation (void *cls)
               "Found ready deposit for %s, aggregating\n",
               TALER_B2S (&au_active.merchant_pub));
   qs = db_plugin->iterate_matching_deposits (db_plugin->cls,
-                                             session,
                                              &au_active.h_wire,
                                              &au_active.merchant_pub,
                                              &aggregate_cb,
@@ -741,8 +722,7 @@ run_aggregation (void *cls)
     GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                 "Failed to execute deposit iteration!\n");
     cleanup_au (&au_active);
-    db_plugin->rollback (db_plugin->cls,
-                         session);
+    db_plugin->rollback (db_plugin->cls);
     global_ret = EXIT_FAILURE;
     GNUNET_SCHEDULER_shutdown ();
     return;
@@ -752,8 +732,7 @@ run_aggregation (void *cls)
     /* serializiability issue, try again */
     GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                 "Serialization issue, trying again later!\n");
-    db_plugin->rollback (db_plugin->cls,
-                         session);
+    db_plugin->rollback (db_plugin->cls);
     cleanup_au (&au_active);
     GNUNET_assert (NULL == task);
     task = GNUNET_SCHEDULER_add_now (&run_aggregation,
@@ -780,14 +759,12 @@ run_aggregation (void *cls)
                 TALER_amount2s (&au_active.final_amount));
     /* Rollback ongoing transaction, as we will not use the respective
        WTID and thus need to remove the tracking data */
-    db_plugin->rollback (db_plugin->cls,
-                         session);
+    db_plugin->rollback (db_plugin->cls);
 
     /* There were results, just the value was too low.  Start another
        transaction to mark all* of the selected deposits as minor! */
     if (GNUNET_OK !=
         db_plugin->start (db_plugin->cls,
-                          session,
                           "aggregator mark tiny transactions"))
     {
       GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
@@ -799,14 +776,12 @@ run_aggregation (void *cls)
     }
     /* Mark transactions by row_id as minor */
     qs = db_plugin->mark_deposit_tiny (db_plugin->cls,
-                                       session,
                                        au_active.row_id);
     if (0 <= qs)
     {
       for (unsigned int i = 0; i<au_active.rows_offset; i++)
       {
         qs = db_plugin->mark_deposit_tiny (db_plugin->cls,
-                                           session,
                                            au_active.additional_rows[i]);
         if (0 > qs)
           break;
@@ -816,8 +791,7 @@ run_aggregation (void *cls)
     {
       GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                   "Serialization issue, trying again later!\n");
-      db_plugin->rollback (db_plugin->cls,
-                           session);
+      db_plugin->rollback (db_plugin->cls);
       cleanup_au (&au_active);
       /* start again */
       GNUNET_assert (NULL == task);
@@ -827,15 +801,14 @@ run_aggregation (void *cls)
     }
     if (GNUNET_DB_STATUS_HARD_ERROR == qs)
     {
-      db_plugin->rollback (db_plugin->cls,
-                           session);
+      db_plugin->rollback (db_plugin->cls);
       cleanup_au (&au_active);
       global_ret = EXIT_FAILURE;
       GNUNET_SCHEDULER_shutdown ();
       return;
     }
     /* commit */
-    (void) commit_or_warn (session);
+    (void) commit_or_warn ();
     cleanup_au (&au_active);
 
     /* start again */
@@ -877,7 +850,6 @@ run_aggregation (void *cls)
                 (unsigned int) buf_size);
     /* Commit our intention to execute the wire transfer! */
     qs = db_plugin->wire_prepare_data_insert (db_plugin->cls,
-                                              session,
                                               au_active.wa->method,
                                               buf,
                                               buf_size);
@@ -887,7 +859,6 @@ run_aggregation (void *cls)
      table constraints */
   if (qs >= 0)
     qs = db_plugin->store_wire_transfer_out (db_plugin->cls,
-                                             session,
                                              au_active.execution_time,
                                              &au_active.wtid,
                                              au_active.wire,
@@ -899,8 +870,7 @@ run_aggregation (void *cls)
   {
     GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                 "Serialization issue for prepared wire data; trying again later!\n");
-    db_plugin->rollback (db_plugin->cls,
-                         session);
+    db_plugin->rollback (db_plugin->cls);
     /* start again */
     GNUNET_assert (NULL == task);
     task = GNUNET_SCHEDULER_add_now (&run_aggregation,
@@ -910,8 +880,7 @@ run_aggregation (void *cls)
   if (GNUNET_DB_STATUS_HARD_ERROR == qs)
   {
     GNUNET_break (0);
-    db_plugin->rollback (db_plugin->cls,
-                         session);
+    db_plugin->rollback (db_plugin->cls);
     /* die hard */
     global_ret = EXIT_FAILURE;
     GNUNET_SCHEDULER_shutdown ();
@@ -923,7 +892,7 @@ run_aggregation (void *cls)
 
   /* Now we can finally commit the overall transaction, as we are
      again consistent if all of this passes. */
-  switch (commit_or_warn (session))
+  switch (commit_or_warn ())
   {
   case GNUNET_DB_STATUS_SOFT_ERROR:
     /* try again */
diff --git a/src/exchange/taler-exchange-closer.c b/src/exchange/taler-exchange-closer.c
index 89e439998..926c93554 100644
--- a/src/exchange/taler-exchange-closer.c
+++ b/src/exchange/taler-exchange-closer.c
@@ -1,6 +1,6 @@
 /*
   This file is part of TALER
-  Copyright (C) 2016-2020 Taler Systems SA
+  Copyright (C) 2016-2021 Taler Systems SA
 
   TALER is free software; you can redistribute it and/or modify it under the
   terms of the GNU Affero General Public License as published by the Free Software
@@ -174,16 +174,14 @@ parse_wirewatch_config (void)
 /**
  * Perform a database commit. If it fails, print a warning.
  *
- * @param session session to perform the commit for.
  * @return status of commit
  */
 static enum GNUNET_DB_QueryStatus
-commit_or_warn (struct TALER_EXCHANGEDB_Session *session)
+commit_or_warn (void)
 {
   enum GNUNET_DB_QueryStatus qs;
 
-  qs = db_plugin->commit (db_plugin->cls,
-                          session);
+  qs = db_plugin->commit (db_plugin->cls);
   if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
     return qs;
   GNUNET_log ((GNUNET_DB_STATUS_SOFT_ERROR == qs)
@@ -195,26 +193,12 @@ commit_or_warn (struct TALER_EXCHANGEDB_Session *session)
 
 
 /**
- * Closure for #expired_reserve_cb().
- */
-struct ExpiredReserveContext
-{
-
-  /**
-   * Database session we are using.
-   */
-  struct TALER_EXCHANGEDB_Session *session;
-
-};
-
-
-/**
  * Function called with details about expired reserves.
  * We trigger the reserve closure by inserting the respective
  * closing record and prewire instructions into the respective
  * tables.
  *
- * @param cls a `struct ExpiredReserveContext *`
+ * @param cls NULL
  * @param reserve_pub public key of the reserve
  * @param left amount left in the reserve
  * @param account_payto_uri information about the bank account that initially
@@ -229,8 +213,6 @@ expired_reserve_cb (void *cls,
                     const char *account_payto_uri,
                     struct GNUNET_TIME_Absolute expiration_date)
 {
-  struct ExpiredReserveContext *erc = cls;
-  struct TALER_EXCHANGEDB_Session *session = erc->session;
   struct GNUNET_TIME_Absolute now;
   struct TALER_WireTransferIdentifierRawP wtid;
   struct TALER_Amount amount_without_fee;
@@ -239,6 +221,7 @@ expired_reserve_cb (void *cls,
   enum GNUNET_DB_QueryStatus qs;
   const struct TALER_EXCHANGEDB_AccountInfo *wa;
 
+  (void) cls;
   /* NOTE: potential optimization: use custom SQL API to not
      fetch this: */
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
@@ -269,7 +252,6 @@ expired_reserve_cb (void *cls,
     enum GNUNET_DB_QueryStatus qs;
 
     qs = db_plugin->get_wire_fee (db_plugin->cls,
-                                  session,
                                   wa->method,
                                   expiration_date,
                                   &start_date,
@@ -326,7 +308,6 @@ expired_reserve_cb (void *cls,
                       sizeof (*reserve_pub)));
   if (GNUNET_SYSERR != ret)
     qs = db_plugin->insert_reserve_closed (db_plugin->cls,
-                                           session,
                                            reserve_pub,
                                            now,
                                            account_payto_uri,
@@ -356,7 +337,7 @@ expired_reserve_cb (void *cls,
     /* Reserve balance was almost zero OR soft error */
     GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                 "Reserve was virtually empty, moving on\n");
-    (void) commit_or_warn (session);
+    (void) commit_or_warn ();
     return qs;
   }
 
@@ -373,7 +354,6 @@ expired_reserve_cb (void *cls,
                                  &buf_size);
     /* Commit our intention to execute the wire transfer! */
     qs = db_plugin->wire_prepare_data_insert (db_plugin->cls,
-                                              session,
                                               wa->method,
                                               buf,
                                               buf_size);
@@ -404,17 +384,16 @@ expired_reserve_cb (void *cls,
 static void
 run_reserve_closures (void *cls)
 {
-  struct TALER_EXCHANGEDB_Session *session;
   enum GNUNET_DB_QueryStatus qs;
-  struct ExpiredReserveContext erc;
   struct GNUNET_TIME_Absolute now;
 
   (void) cls;
   task = NULL;
-  if (NULL == (session = db_plugin->get_session (db_plugin->cls)))
+  if (GNUNET_SYSERR ==
+      db_plugin->preflight (db_plugin->cls))
   {
     GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                "Failed to obtain database session!\n");
+                "Failed to obtain database connection!\n");
     global_ret = EXIT_FAILURE;
     GNUNET_SCHEDULER_shutdown ();
     return;
@@ -422,7 +401,6 @@ run_reserve_closures (void *cls)
 
   if (GNUNET_OK !=
       db_plugin->start (db_plugin->cls,
-                        session,
                         "aggregator reserve closures"))
   {
     GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
@@ -431,30 +409,26 @@ run_reserve_closures (void *cls)
     GNUNET_SCHEDULER_shutdown ();
     return;
   }
-  erc.session = session;
   now = GNUNET_TIME_absolute_get ();
   (void) GNUNET_TIME_round_abs (&now);
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
               "Checking for reserves to close by date %s\n",
               GNUNET_STRINGS_absolute_time_to_string (now));
   qs = db_plugin->get_expired_reserves (db_plugin->cls,
-                                        session,
                                         now,
                                         &expired_reserve_cb,
-                                        &erc);
+                                        NULL);
   GNUNET_assert (1 >= qs);
   switch (qs)
   {
   case GNUNET_DB_STATUS_HARD_ERROR:
     GNUNET_break (0);
-    db_plugin->rollback (db_plugin->cls,
-                         session);
+    db_plugin->rollback (db_plugin->cls);
     global_ret = EXIT_FAILURE;
     GNUNET_SCHEDULER_shutdown ();
     return;
   case GNUNET_DB_STATUS_SOFT_ERROR:
-    db_plugin->rollback (db_plugin->cls,
-                         session);
+    db_plugin->rollback (db_plugin->cls);
     GNUNET_assert (NULL == task);
     task = GNUNET_SCHEDULER_add_now (&run_reserve_closures,
                                      NULL);
@@ -462,8 +436,7 @@ run_reserve_closures (void *cls)
   case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
     GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                 "No more idle reserves to close, going to sleep.\n");
-    db_plugin->rollback (db_plugin->cls,
-                         session);
+    db_plugin->rollback (db_plugin->cls);
     GNUNET_assert (NULL == task);
     if (GNUNET_YES == test_mode)
     {
@@ -477,7 +450,7 @@ run_reserve_closures (void *cls)
     }
     return;
   case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
-    (void) commit_or_warn (session);
+    (void) commit_or_warn ();
     GNUNET_assert (NULL == task);
     task = GNUNET_SCHEDULER_add_now (&run_reserve_closures,
                                      NULL);
diff --git a/src/exchange/taler-exchange-httpd.c b/src/exchange/taler-exchange-httpd.c
index c06695e4d..627ac00f9 100644
--- a/src/exchange/taler-exchange-httpd.c
+++ b/src/exchange/taler-exchange-httpd.c
@@ -1,6 +1,6 @@
 /*
   This file is part of TALER
-  Copyright (C) 2014-2020 Taler Systems SA
+  Copyright (C) 2014-2021 Taler Systems SA
 
   TALER is free software; you can redistribute it and/or modify it under the
   terms of the GNU Affero General Public License as published by the Free Software
@@ -34,7 +34,6 @@
 #include "taler-exchange-httpd_deposits_get.h"
 #include "taler-exchange-httpd_keys.h"
 #include "taler-exchange-httpd_link.h"
-#include "taler-exchange-httpd_loop.h"
 #include "taler-exchange-httpd_management.h"
 #include "taler-exchange-httpd_melt.h"
 #include "taler-exchange-httpd_mhd.h"
@@ -53,7 +52,7 @@
 /**
  * Backlog for listen operation on unix domain sockets.
  */
-#define UNIX_BACKLOG 500
+#define UNIX_BACKLOG 50
 
 
 /**
@@ -67,7 +66,7 @@ int TEH_allow_keys_timetravel;
 /**
  * The exchange's configuration (global)
  */
-struct GNUNET_CONFIGURATION_Handle *TEH_cfg;
+const struct GNUNET_CONFIGURATION_Handle *TEH_cfg;
 
 /**
  * How long is caching /keys allowed at most? (global)
@@ -101,16 +100,14 @@ char *TEH_currency;
 static unsigned int connection_timeout = 30;
 
 /**
- * How many threads to use.
- * The default value (0) sets the actual number of threads
- * based on the number of available cores.
+ * -C command-line flag given?
  */
-static unsigned int num_threads = 0;
+static int connection_close;
 
 /**
- * The HTTP Daemon.
+ * Value to return from main()
  */
-static struct MHD_Daemon *mhd;
+static int global_ret;
 
 /**
  * Port to run the daemon on.
@@ -118,17 +115,6 @@ static struct MHD_Daemon *mhd;
 static uint16_t serve_port;
 
 /**
- * Path for the unix domain-socket
- * to run the daemon on.
- */
-static char *serve_unixpath;
-
-/**
- * File mode for unix-domain socket.
- */
-static mode_t unixpath_mode;
-
-/**
  * Counter for the number of requests this HTTP has processed so far.
  */
 static unsigned long long req_count;
@@ -302,11 +288,8 @@ handle_mhd_completion_callback (void *cls,
 
   TALER_MHD_parse_post_cleanup_callback (rc->opaque_post_parsing_context);
   /* Sanity-check that we didn't leave any transactions hanging */
-  /* NOTE: In high-performance production, we could consider
-     removing this as it should not be needed and might be costly
-     (to be benchmarked). */
-  TEH_plugin->preflight (TEH_plugin->cls,
-                         TEH_plugin->get_session (TEH_plugin->cls));
+  GNUNET_break (GNUNET_OK ==
+                TEH_plugin->preflight (TEH_plugin->cls));
   GNUNET_free (rc);
   *con_cls = NULL;
   GNUNET_async_scope_restore (&old_scope);
@@ -1179,18 +1162,6 @@ exchange_serve_process_config (void)
                 "Failed to initialize DB subsystem\n");
     return GNUNET_SYSERR;
   }
-
-  if (GNUNET_OK !=
-      TALER_MHD_parse_config (TEH_cfg,
-                              "exchange",
-                              &serve_port,
-                              &serve_unixpath,
-                              &unixpath_mode))
-  {
-    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                "Failed to setup HTTPd subsystem\n");
-    return GNUNET_SYSERR;
-  }
   return GNUNET_OK;
 }
 
@@ -1248,16 +1219,11 @@ write_stats (void)
 /* Developer logic for supporting the `-f' option. */
 #if HAVE_DEVELOPER
 
-
 /**
  * Option `-f' (specifies an input file to give to the HTTP server).
  */
 static char *input_filename;
 
-/**
- * We finished handling the request and should now terminate.
- */
-static int do_terminate;
 
 /**
  * Run 'nc' or 'ncat' as a fake HTTP client using #input_filename
@@ -1277,7 +1243,8 @@ run_fake_client (void)
                    "-"))
     fd = STDIN_FILENO;
   else
-    fd = open (input_filename, O_RDONLY);
+    fd = open (input_filename,
+               O_RDONLY);
   if (-1 == fd)
   {
     fprintf (stderr,
@@ -1325,6 +1292,50 @@ run_fake_client (void)
 
 
 /**
+ * Run the exchange to serve a single request only, without threads.
+ *
+ * @return #GNUNET_OK on success
+ */
+static void
+run_single_request (void)
+{
+  pid_t xfork;
+
+  xfork = fork ();
+  if (-1 == xfork)
+  {
+    global_ret = EXIT_FAILURE;
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
+  if (0 == xfork)
+  {
+    pid_t cld;
+
+    cld = run_fake_client ();
+    if (-1 == cld)
+      _exit (EXIT_FAILURE);
+    _exit (EXIT_SUCCESS);
+  }
+
+  {
+    int status;
+
+    if (xfork != waitpid (xfork,
+                          &status,
+                          0))
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                  "Waiting for `nc' child failed: %s\n",
+                  strerror (errno));
+  }
+}
+
+
+/* end of HAVE_DEVELOPER */
+#endif
+
+
+/**
  * Signature of the callback used by MHD to notify the application
  * about completed connections.  If we are running in test-mode with
  * an #input_filename, this function is used to terminate the HTTPD
@@ -1344,240 +1355,138 @@ connection_done (void *cls,
   (void) cls;
   (void) connection;
   (void) socket_context;
+
+#if HAVE_DEVELOPER
   /* We only act if the connection is closed. */
   if (MHD_CONNECTION_NOTIFY_CLOSED != toe)
     return;
-  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-              "Connection done!\n");
-  do_terminate = GNUNET_YES;
+  if (NULL != input_filename)
+    GNUNET_SCHEDULER_shutdown ();
+#endif
 }
 
 
 /**
- * Run the exchange to serve a single request only, without threads.
+ * Function run on shutdown.
  *
- * @return #GNUNET_OK on success
+ * @param cls NULL
  */
-static int
-run_single_request (void)
+static void
+do_shutdown (void *cls)
 {
-  pid_t cld;
-  int status;
-
-  /* run only the testfile input, then terminate */
-  mhd
-    = MHD_start_daemon (MHD_USE_PIPE_FOR_SHUTDOWN
-                        | MHD_USE_DEBUG | MHD_USE_DUAL_STACK
-                        | MHD_USE_TCP_FASTOPEN,
-                        0, /* pick free port */
-                        NULL, NULL,
-                        &handle_mhd_request, NULL,
-                        MHD_OPTION_LISTEN_BACKLOG_SIZE, (unsigned int) 10,
-                        MHD_OPTION_EXTERNAL_LOGGER, &TALER_MHD_handle_logs,
-                        NULL,
-                        MHD_OPTION_NOTIFY_COMPLETED,
-                        &handle_mhd_completion_callback, NULL,
-                        MHD_OPTION_CONNECTION_TIMEOUT, connection_timeout,
-                        MHD_OPTION_NOTIFY_CONNECTION, &connection_done, NULL,
-                        MHD_OPTION_END);
-  if (NULL == mhd)
-  {
-    fprintf (stderr,
-             "Failed to start HTTP server.\n");
-    return GNUNET_SYSERR;
-  }
-  serve_port = MHD_get_daemon_info (mhd,
-                                    MHD_DAEMON_INFO_BIND_PORT)->port;
-  cld = run_fake_client ();
-  if (-1 == cld)
-    return GNUNET_SYSERR;
-  /* run the event loop until #connection_done() was called */
-  while (GNUNET_NO == do_terminate)
-  {
-    fd_set rs;
-    fd_set ws;
-    fd_set es;
-    struct timeval tv;
-    MHD_UNSIGNED_LONG_LONG timeout;
-    int maxsock = -1;
-    int have_tv;
-
-    FD_ZERO (&rs);
-    FD_ZERO (&ws);
-    FD_ZERO (&es);
-    if (MHD_YES !=
-        MHD_get_fdset (mhd,
-                       &rs,
-                       &ws,
-                       &es,
-                       &maxsock))
-    {
-      GNUNET_break (0);
-      return GNUNET_SYSERR;
-    }
-    have_tv = MHD_get_timeout (mhd,
-                               &timeout);
-    tv.tv_sec = timeout / 1000;
-    tv.tv_usec = 1000 * (timeout % 1000);
-    if (-1 == select (maxsock + 1,
-                      &rs,
-                      &ws,
-                      &es,
-                      have_tv ? &tv : NULL))
-    {
-      GNUNET_break (0);
-      return GNUNET_SYSERR;
-    }
-    MHD_run (mhd);
-  }
-  {
-    MHD_socket sock = MHD_quiesce_daemon (mhd);
+  struct MHD_Daemon *mhd;
+  (void) cls;
 
-    TEH_resume_keys_requests (true);
-    TEH_reserves_get_cleanup ();
+  mhd = TALER_MHD_daemon_stop ();
+  TEH_resume_keys_requests (true);
+  TEH_reserves_get_cleanup ();
+  if (NULL != mhd)
     MHD_stop_daemon (mhd);
-    GNUNET_break (0 == close (sock));
-  }
-  mhd = NULL;
-  if (cld != waitpid (cld,
-                      &status,
-                      0))
-    fprintf (stderr,
-             "Waiting for `nc' child failed: %s\n",
-             strerror (errno));
-  return GNUNET_OK;
+  TALER_EXCHANGEDB_plugin_unload (TEH_plugin);
+  TEH_WIRE_done ();
 }
 
 
-/* end of HAVE_DEVELOPER */
-#endif
-
-
 /**
- * Run the ordinary multi-threaded main loop and the logic to
- * wait for CTRL-C.
+ * Main function that will be run by the scheduler.
  *
- * @param fh listen socket
- * @param argv command line arguments
- * @return #GNUNET_OK on success
+ * @param cls closure
+ * @param args remaining command-line arguments
+ * @param cfgfile name of the configuration file used (for saving, can be
+ *        NULL!)
+ * @param config configuration
  */
-static int
-run_main_loop (int fh,
-               char *const *argv)
+static void
+run (void *cls,
+     char *const *args,
+     const char *cfgfile,
+     const struct GNUNET_CONFIGURATION_Handle *config)
 {
-  int ret;
-
-  GNUNET_assert (0 < num_threads);
-
-  mhd
-    = MHD_start_daemon (MHD_USE_SELECT_INTERNALLY | MHD_USE_PIPE_FOR_SHUTDOWN
-                        | MHD_USE_DEBUG | MHD_USE_DUAL_STACK
-                        | MHD_USE_INTERNAL_POLLING_THREAD
-                        | MHD_ALLOW_SUSPEND_RESUME
-                        | MHD_USE_TCP_FASTOPEN,
-                        (-1 == fh) ? serve_port : 0,
-                        NULL, NULL,
-                        &handle_mhd_request, NULL,
-                        MHD_OPTION_THREAD_POOL_SIZE, (unsigned int) num_threads,
-                        MHD_OPTION_LISTEN_BACKLOG_SIZE, (unsigned int) 1024,
-                        MHD_OPTION_LISTEN_SOCKET, fh,
-                        MHD_OPTION_EXTERNAL_LOGGER, &TALER_MHD_handle_logs,
-                        NULL,
-                        MHD_OPTION_NOTIFY_COMPLETED,
-                        &handle_mhd_completion_callback, NULL,
-                        MHD_OPTION_CONNECTION_TIMEOUT, connection_timeout,
-                        MHD_OPTION_END);
-  if (NULL == mhd)
+  enum TALER_MHD_GlobalOptions go;
+  int fh;
+
+  go = TALER_MHD_GO_NONE;
+  if (connection_close)
+    go |= TALER_MHD_GO_FORCE_CONNECTION_CLOSE;
+  TALER_MHD_setup (go);
+  TEH_cfg = config;
+
+  if (GNUNET_OK !=
+      exchange_serve_process_config ())
   {
-    fprintf (stderr,
-             "Failed to start HTTP server.\n");
-    return GNUNET_SYSERR;
+    global_ret = EXIT_NOTCONFIGURED;
+    GNUNET_SCHEDULER_shutdown ();
+    return;
   }
-
-  atexit (&write_stats);
-  ret = TEH_loop_run ();
-  switch (ret)
+  if (GNUNET_OK !=
+      TEH_WIRE_init ())
   {
-  case GNUNET_OK:
-  case GNUNET_SYSERR:
-    {
-      MHD_socket sock = MHD_quiesce_daemon (mhd);
+    global_ret = EXIT_FAILURE;
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
+  if (GNUNET_OK !=
+      TEH_keys_init ())
+  {
+    global_ret = EXIT_FAILURE;
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
 
-      TEH_resume_keys_requests (true);
-      TEH_reserves_get_cleanup ();
-      MHD_stop_daemon (mhd);
-      GNUNET_break (0 == close (sock));
-    }
-    mhd = NULL;
-    break;
-  case GNUNET_NO:
+  TEH_load_terms (TEH_cfg);
+  GNUNET_SCHEDULER_add_shutdown (&do_shutdown,
+                                 NULL);
+  fh = TALER_MHD_bind (TEH_cfg,
+                       "exchange",
+                       &serve_port);
+  if ( (0 == serve_port) &&
+       (-1 == fh) )
+  {
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
+  {
+    struct MHD_Daemon *mhd;
+
+    mhd = MHD_start_daemon (MHD_USE_SUSPEND_RESUME
+                            | MHD_USE_PIPE_FOR_SHUTDOWN
+                            | MHD_USE_DEBUG | MHD_USE_DUAL_STACK
+                            | MHD_USE_TCP_FASTOPEN,
+                            (-1 == fh) ? serve_port : 0,
+                            NULL, NULL,
+                            &handle_mhd_request, NULL,
+                            MHD_OPTION_LISTEN_BACKLOG_SIZE,
+                            (unsigned int) 1024,
+                            MHD_OPTION_LISTEN_SOCKET,
+                            fh,
+                            MHD_OPTION_EXTERNAL_LOGGER,
+                            &TALER_MHD_handle_logs,
+                            NULL,
+                            MHD_OPTION_NOTIFY_COMPLETED,
+                            &handle_mhd_completion_callback,
+                            NULL,
+                            MHD_OPTION_NOTIFY_CONNECTION,
+                            &connection_done,
+                            NULL,
+                            MHD_OPTION_CONNECTION_TIMEOUT,
+                            connection_timeout,
+                            MHD_OPTION_END);
+    if (NULL == mhd)
     {
-      MHD_socket sock = MHD_quiesce_daemon (mhd);
-      pid_t chld;
-      int flags;
-
-      /* Set flags to make 'sock' inherited by child */
-      flags = fcntl (sock, F_GETFD);
-      GNUNET_assert (-1 != flags);
-      flags &= ~FD_CLOEXEC;
-      GNUNET_assert (-1 != fcntl (sock,
-                                  F_SETFD,
-                                  flags));
-      chld = fork ();
-      if (-1 == chld)
-      {
-        /* fork() failed, continue clean up, unhappily */
-        GNUNET_log_strerror (GNUNET_ERROR_TYPE_ERROR,
-                             "fork");
-      }
-      if (0 == chld)
-      {
-        char pids[12];
-
-        /* exec another taler-exchange-httpd, passing on the listen socket;
-           as in systemd it is expected to be on FD #3 */
-        if (3 != dup2 (sock, 3))
-        {
-          GNUNET_log_strerror (GNUNET_ERROR_TYPE_ERROR,
-                               "dup2");
-          _exit (1);
-        }
-        /* Tell the child that it is the desired recipient for FD #3 */
-        GNUNET_snprintf (pids,
-                         sizeof (pids),
-                         "%u",
-                         getpid ());
-        setenv ("LISTEN_PID", pids, 1);
-        setenv ("LISTEN_FDS", "1", 1);
-        /* Finally, exec the (presumably) more recent exchange binary */
-        execvp ("taler-exchange-httpd",
-                argv);
-        GNUNET_log_strerror (GNUNET_ERROR_TYPE_ERROR,
-                             "execvp");
-        _exit (1);
-      }
-      /* we're the original process, handle remaining contextions
-         before exiting; as the listen socket is no longer used,
-         close it here */
-      GNUNET_break (0 == close (sock));
-      while (0 != MHD_get_daemon_info (mhd,
-                                       MHD_DAEMON_INFO_CURRENT_CONNECTIONS)->
-             num_connections)
-        sleep (1);
-      /* Now we're really done, practice clean shutdown */
-      TEH_resume_keys_requests (true);
-      TEH_reserves_get_cleanup ();
-      MHD_stop_daemon (mhd);
+      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                  "Failed to launch HTTP service. Is the port in use?\n");
+      GNUNET_SCHEDULER_shutdown ();
+      return;
     }
-    break;
-  default:
-    GNUNET_break (0);
-    TEH_resume_keys_requests (true);
-    MHD_stop_daemon (mhd);
-    break;
+    global_ret = EXIT_SUCCESS;
+    TALER_MHD_daemon_start (mhd);
   }
+  atexit (&write_stats);
 
-  return ret;
+#if HAVE_DEVELOPER
+  if (NULL != input_filename)
+    run_single_request ();
+#endif
 }
 
 
@@ -1592,10 +1501,6 @@ int
 main (int argc,
       char *const *argv)
 {
-  char *cfgfile = NULL;
-  char *loglev = NULL;
-  char *logfile = NULL;
-  int connection_close = GNUNET_NO;
   const struct GNUNET_GETOPT_CommandLineOption options[] = {
     GNUNET_GETOPT_option_flag ('a',
                                "allow-timetravel",
@@ -1605,7 +1510,6 @@ main (int argc,
                                "connection-close",
                                "force HTTP connections to be closed after each request",
                                &connection_close),
-    GNUNET_GETOPT_option_cfgfile (&cfgfile),
     GNUNET_GETOPT_option_uint ('t',
                                "timeout",
                                "SECONDS",
@@ -1613,11 +1517,6 @@ main (int argc,
                                &connection_timeout),
     GNUNET_GETOPT_option_timetravel ('T',
                                      "timetravel"),
-    GNUNET_GETOPT_option_uint ('n',
-                               "num-threads",
-                               "NUM_THREADS",
-                               "size of the thread pool",
-                               &num_threads),
 #if HAVE_DEVELOPER
     GNUNET_GETOPT_option_filename ('f',
                                    "file-input",
@@ -1627,141 +1526,22 @@ main (int argc,
 #endif
     GNUNET_GETOPT_option_help (
       "HTTP server providing a RESTful API to access a Taler exchange"),
-    GNUNET_GETOPT_option_loglevel (&loglev),
-    GNUNET_GETOPT_option_logfile (&logfile),
     GNUNET_GETOPT_option_version (VERSION "-" VCS_VERSION),
     GNUNET_GETOPT_OPTION_END
   };
-  int ret;
-  const char *listen_pid;
-  const char *listen_fds;
-  int fh = -1;
-  enum TALER_MHD_GlobalOptions go;
+  enum GNUNET_GenericReturnValue ret;
 
   TALER_OS_init ();
-  ret = GNUNET_GETOPT_run ("taler-exchange-httpd",
-                           options,
-                           argc, argv);
+  ret = GNUNET_PROGRAM_run (argc, argv,
+                            "taler-exchange-httpd",
+                            "Taler exchange HTTP service",
+                            options,
+                            &run, NULL);
   if (GNUNET_SYSERR == ret)
     return EXIT_INVALIDARGUMENT;
   if (GNUNET_NO == ret)
     return EXIT_SUCCESS;
-  if (0 == num_threads)
-  {
-    cpu_set_t mask;
-    GNUNET_assert (0 ==
-                   sched_getaffinity (0,
-                                      sizeof (cpu_set_t),
-                                      &mask));
-    num_threads = CPU_COUNT (&mask);
-  }
-  go = TALER_MHD_GO_NONE;
-  if (connection_close)
-    go |= TALER_MHD_GO_FORCE_CONNECTION_CLOSE;
-  TALER_MHD_setup (go);
-  GNUNET_assert (GNUNET_OK ==
-                 GNUNET_log_setup ("taler-exchange-httpd",
-                                   (NULL == loglev) ? "INFO" : loglev,
-                                   logfile));
-  GNUNET_free (loglev);
-  GNUNET_free (logfile);
-  if (NULL == cfgfile)
-    cfgfile = GNUNET_CONFIGURATION_default_filename ();
-  if (NULL == cfgfile)
-  {
-    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                "Can't find default configuration file.\n");
-    return EXIT_NOTCONFIGURED;
-  }
-
-  TEH_cfg = GNUNET_CONFIGURATION_create ();
-  if (GNUNET_SYSERR ==
-      GNUNET_CONFIGURATION_load (TEH_cfg,
-                                 cfgfile))
-  {
-    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                "Malformed configuration file `%s', exit ...\n",
-                cfgfile);
-    GNUNET_free (cfgfile);
-    return EXIT_NOTCONFIGURED;
-  }
-  GNUNET_free (cfgfile);
-  if (GNUNET_OK !=
-      exchange_serve_process_config ())
-    return EXIT_NOTCONFIGURED;
-  TEH_load_terms (TEH_cfg);
-
-  /* check for systemd-style FD passing */
-  listen_pid = getenv ("LISTEN_PID");
-  listen_fds = getenv ("LISTEN_FDS");
-  if ( (NULL != listen_pid) &&
-       (NULL != listen_fds) &&
-       (getpid () == strtol (listen_pid,
-                             NULL,
-                             10)) &&
-       (1 == strtoul (listen_fds,
-                      NULL,
-                      10)) )
-  {
-    int flags;
-
-    fh = 3;
-    flags = fcntl (fh,
-                   F_GETFD);
-    if ( (-1 == flags) &&
-         (EBADF == errno) )
-    {
-      GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                  "Bad listen socket passed, ignored\n");
-      fh = -1;
-    }
-    flags |= FD_CLOEXEC;
-    if ( (-1 != fh) &&
-         (0 != fcntl (fh,
-                      F_SETFD,
-                      flags)) )
-      GNUNET_log_strerror (GNUNET_ERROR_TYPE_ERROR,
-                           "fcntl");
-    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                "Successfully obtained listen socket from hypervisor\n");
-  }
-
-  /* initialize #internal_key_state with an RC of 1 */
-  if (GNUNET_OK !=
-      TEH_WIRE_init ())
-    return EXIT_FAILURE;
-  if (GNUNET_OK !=
-      TEH_keys_init ())
-    return EXIT_FAILURE;
-  ret = TEH_loop_init ();
-  if (GNUNET_OK == ret)
-  {
-#if HAVE_DEVELOPER
-    if (NULL != input_filename)
-    {
-      ret = run_single_request ();
-    }
-    else
-#endif
-    {
-      /* consider unix path */
-      if ( (-1 == fh) &&
-           (NULL != serve_unixpath) )
-      {
-        fh = TALER_MHD_open_unix_path (serve_unixpath,
-                                       unixpath_mode);
-        if (-1 == fh)
-          return EXIT_NOPERMISSION; /* at least most likely */
-      }
-      ret = run_main_loop (fh,
-                           argv);
-    }
-    /* release signal handlers */
-    TEH_loop_done ();
-  }
-  TALER_EXCHANGEDB_plugin_unload (TEH_plugin);
-  TEH_WIRE_done ();
-  return (GNUNET_SYSERR == ret) ? EXIT_FAILURE : EXIT_SUCCESS;
+  return global_ret;
 }
 
 
diff --git a/src/exchange/taler-exchange-httpd.h b/src/exchange/taler-exchange-httpd.h
index eaecc9720..e43426488 100644
--- a/src/exchange/taler-exchange-httpd.h
+++ b/src/exchange/taler-exchange-httpd.h
@@ -42,7 +42,7 @@ extern struct GNUNET_TIME_Relative TEH_reserve_closing_delay;
 /**
  * The exchange's configuration.
  */
-extern struct GNUNET_CONFIGURATION_Handle *TEH_cfg;
+extern const struct GNUNET_CONFIGURATION_Handle *TEH_cfg;
 
 /**
  * Main directory with exchange data.
diff --git a/src/exchange/taler-exchange-httpd_auditors.c b/src/exchange/taler-exchange-httpd_auditors.c
index f3c061e39..34e640ad7 100644
--- a/src/exchange/taler-exchange-httpd_auditors.c
+++ b/src/exchange/taler-exchange-httpd_auditors.c
@@ -65,7 +65,6 @@ struct AddAuditorDenomContext
  *
  * @param cls closure with a `struct AddAuditorDenomContext`
  * @param connection MHD request which triggered the transaction
- * @param session database session to use
  * @param[out] mhd_ret set to MHD response status for @a connection,
  *             if transaction failed (!)
  * @return transaction status
@@ -73,7 +72,6 @@ struct AddAuditorDenomContext
 static enum GNUNET_DB_QueryStatus
 add_auditor_denom_sig (void *cls,
                        struct MHD_Connection *connection,
-                       struct TALER_EXCHANGEDB_Session *session,
                        MHD_RESULT *mhd_ret)
 {
   struct AddAuditorDenomContext *awc = cls;
@@ -84,7 +82,6 @@ add_auditor_denom_sig (void *cls,
 
   qs = TEH_plugin->lookup_denomination_key (
     TEH_plugin->cls,
-    session,
     awc->h_denom_pub,
     &meta);
   if (qs < 0)
@@ -110,7 +107,6 @@ add_auditor_denom_sig (void *cls,
 
   qs = TEH_plugin->lookup_auditor_status (
     TEH_plugin->cls,
-    session,
     awc->auditor_pub,
     &auditor_url,
     &enabled);
@@ -174,7 +170,6 @@ add_auditor_denom_sig (void *cls,
   GNUNET_free (auditor_url);
 
   qs = TEH_plugin->insert_auditor_denom_sig (TEH_plugin->cls,
-                                             session,
                                              awc->h_denom_pub,
                                              awc->auditor_pub,
                                              &awc->auditor_sig);
diff --git a/src/exchange/taler-exchange-httpd_db.c b/src/exchange/taler-exchange-httpd_db.c
index 8574224af..3c6936497 100644
--- a/src/exchange/taler-exchange-httpd_db.c
+++ b/src/exchange/taler-exchange-httpd_db.c
@@ -45,21 +45,18 @@
  *
  * @param coin the coin to make known
  * @param connection MHD request context
- * @param session database session and transaction to use
  * @param[out] mhd_ret set to MHD status on error
  * @return transaction status, negative on error (@a mhd_ret will be set in this case)
  */
 enum GNUNET_DB_QueryStatus
 TEH_make_coin_known (const struct TALER_CoinPublicInfo *coin,
                      struct MHD_Connection *connection,
-                     struct TALER_EXCHANGEDB_Session *session,
                      MHD_RESULT *mhd_ret)
 {
   enum TALER_EXCHANGEDB_CoinKnownStatus cks;
 
   /* make sure coin is 'known' in database */
   cks = TEH_plugin->ensure_coin_known (TEH_plugin->cls,
-                                       session,
                                        coin);
   switch (cks)
   {
@@ -85,7 +82,6 @@ TEH_make_coin_known (const struct TALER_CoinPublicInfo *coin,
     enum GNUNET_DB_QueryStatus qs;
 
     qs = TEH_plugin->get_coin_transactions (TEH_plugin->cls,
-                                            session,
                                             &coin->coin_pub,
                                             GNUNET_NO,
                                             &tl);
@@ -135,11 +131,10 @@ TEH_DB_run_transaction (struct MHD_Connection *connection,
                         TEH_DB_TransactionCallback cb,
                         void *cb_cls)
 {
-  struct TALER_EXCHANGEDB_Session *session;
-
   if (NULL != mhd_ret)
     *mhd_ret = -1; /* set to invalid value, to help detect bugs */
-  if (NULL == (session = TEH_plugin->get_session (TEH_plugin->cls)))
+  if (GNUNET_OK !=
+      TEH_plugin->preflight (TEH_plugin->cls))
   {
     GNUNET_break (0);
     if (NULL != mhd_ret)
@@ -157,7 +152,6 @@ TEH_DB_run_transaction (struct MHD_Connection *connection,
 
     if (GNUNET_OK !=
         TEH_plugin->start (TEH_plugin->cls,
-                           session,
                            name))
     {
       GNUNET_break (0);
@@ -170,16 +164,13 @@ TEH_DB_run_transaction (struct MHD_Connection *connection,
     }
     qs = cb (cb_cls,
              connection,
-             session,
              mhd_ret);
     if (0 > qs)
-      TEH_plugin->rollback (TEH_plugin->cls,
-                            session);
+      TEH_plugin->rollback (TEH_plugin->cls);
     if (GNUNET_DB_STATUS_HARD_ERROR == qs)
       return GNUNET_SYSERR;
     if (0 <= qs)
-      qs = TEH_plugin->commit (TEH_plugin->cls,
-                               session);
+      qs = TEH_plugin->commit (TEH_plugin->cls);
     if (GNUNET_DB_STATUS_HARD_ERROR == qs)
     {
       if (NULL != mhd_ret)
diff --git a/src/exchange/taler-exchange-httpd_db.h b/src/exchange/taler-exchange-httpd_db.h
index 7e73340b7..c115981d3 100644
--- a/src/exchange/taler-exchange-httpd_db.h
+++ b/src/exchange/taler-exchange-httpd_db.h
@@ -31,14 +31,12 @@
  *
  * @param coin the coin to make known
  * @param connection MHD request context
- * @param session database session and transaction to use
  * @param[out] mhd_ret set to MHD status on error
  * @return transaction status, negative on error (@a mhd_ret will be set in this case)
  */
 enum GNUNET_DB_QueryStatus
 TEH_make_coin_known (const struct TALER_CoinPublicInfo *coin,
                      struct MHD_Connection *connection,
-                     struct TALER_EXCHANGEDB_Session *session,
                      MHD_RESULT *mhd_ret);
 
 
@@ -52,7 +50,6 @@ TEH_make_coin_known (const struct TALER_CoinPublicInfo *coin,
  *
  * @param cls closure
  * @param connection MHD request which triggered the transaction
- * @param session database session to use
  * @param[out] mhd_ret set to MHD response status for @a connection,
  *             if transaction failed (!)
  * @return transaction status
@@ -60,7 +57,6 @@ TEH_make_coin_known (const struct TALER_CoinPublicInfo *coin,
 typedef enum GNUNET_DB_QueryStatus
 (*TEH_DB_TransactionCallback)(void *cls,
                               struct MHD_Connection *connection,
-                              struct TALER_EXCHANGEDB_Session *session,
                               MHD_RESULT *mhd_ret);
 
 
diff --git a/src/exchange/taler-exchange-httpd_deposit.c b/src/exchange/taler-exchange-httpd_deposit.c
index 5ea48c20c..9c4cfdc7e 100644
--- a/src/exchange/taler-exchange-httpd_deposit.c
+++ b/src/exchange/taler-exchange-httpd_deposit.c
@@ -133,14 +133,12 @@ struct DepositContext
  *
  * @param cls a `struct DepositContext`
  * @param connection MHD request context
- * @param session database session and transaction to use
  * @param[out] mhd_ret set to MHD status on error
  * @return transaction status
  */
 static enum GNUNET_DB_QueryStatus
 deposit_precheck (void *cls,
                   struct MHD_Connection *connection,
-                  struct TALER_EXCHANGEDB_Session *session,
                   MHD_RESULT *mhd_ret)
 {
   struct DepositContext *dc = cls;
@@ -149,7 +147,6 @@ deposit_precheck (void *cls,
   enum GNUNET_DB_QueryStatus qs;
 
   qs = TEH_plugin->have_deposit (TEH_plugin->cls,
-                                 session,
                                  deposit,
                                  GNUNET_YES /* check refund deadline */,
                                  &deposit_fee,
@@ -202,14 +199,12 @@ deposit_precheck (void *cls,
  *
  * @param cls a `struct DepositContext`
  * @param connection MHD request context
- * @param session database session and transaction to use
  * @param[out] mhd_ret set to MHD status on error
  * @return transaction status
  */
 static enum GNUNET_DB_QueryStatus
 deposit_transaction (void *cls,
                      struct MHD_Connection *connection,
-                     struct TALER_EXCHANGEDB_Session *session,
                      MHD_RESULT *mhd_ret)
 {
   struct DepositContext *dc = cls;
@@ -220,7 +215,6 @@ deposit_transaction (void *cls,
   /* make sure coin is 'known' in database */
   qs = TEH_make_coin_known (&deposit->coin,
                             connection,
-                            session,
                             mhd_ret);
   if (qs < 0)
     return qs;
@@ -230,7 +224,6 @@ deposit_transaction (void *cls,
      that we are in the transaction scope. */
   qs = deposit_precheck (cls,
                          connection,
-                         session,
                          mhd_ret);
   if (qs < 0)
     return qs;
@@ -244,7 +237,6 @@ deposit_transaction (void *cls,
     struct TALER_EXCHANGEDB_TransactionList *tl;
 
     qs = TEH_plugin->get_coin_transactions (TEH_plugin->cls,
-                                            session,
                                             &deposit->coin.coin_pub,
                                             GNUNET_NO,
                                             &tl);
@@ -292,7 +284,6 @@ deposit_transaction (void *cls,
                                             tl);
   }
   qs = TEH_plugin->insert_deposit (TEH_plugin->cls,
-                                   session,
                                    dc->exchange_timestamp,
                                    deposit);
   if (GNUNET_DB_STATUS_HARD_ERROR == qs)
diff --git a/src/exchange/taler-exchange-httpd_deposits_get.c b/src/exchange/taler-exchange-httpd_deposits_get.c
index f32b88b6d..04e2acb02 100644
--- a/src/exchange/taler-exchange-httpd_deposits_get.c
+++ b/src/exchange/taler-exchange-httpd_deposits_get.c
@@ -203,7 +203,6 @@ handle_wtid_data (void *cls,
  *
  * @param cls closure of type `struct DepositWtidContext *`
  * @param connection MHD request which triggered the transaction
- * @param session database session to use
  * @param[out] mhd_ret set to MHD response status for @a connection,
  *             if transaction failed (!)
  * @return transaction status
@@ -211,14 +210,12 @@ handle_wtid_data (void *cls,
 static enum GNUNET_DB_QueryStatus
 deposits_get_transaction (void *cls,
                           struct MHD_Connection *connection,
-                          struct TALER_EXCHANGEDB_Session *session,
                           MHD_RESULT *mhd_ret)
 {
   struct DepositWtidContext *ctx = cls;
   enum GNUNET_DB_QueryStatus qs;
 
   qs = TEH_plugin->lookup_transfer_by_deposit (TEH_plugin->cls,
-                                               session,
                                                &ctx->tps->h_contract_terms,
                                                &ctx->tps->h_wire,
                                                &ctx->tps->coin_pub,
diff --git a/src/exchange/taler-exchange-httpd_keys.c b/src/exchange/taler-exchange-httpd_keys.c
index 216afd7c5..f37aafbd1 100644
--- a/src/exchange/taler-exchange-httpd_keys.c
+++ b/src/exchange/taler-exchange-httpd_keys.c
@@ -19,7 +19,6 @@
  * @author Christian Grothoff
  */
 #include "platform.h"
-#include <pthread.h>
 #include "taler_json_lib.h"
 #include "taler_mhd_lib.h"
 #include "taler-exchange-httpd.h"
@@ -339,10 +338,9 @@ struct SuspendedKeysRequests
 
 
 /**
- * Thread-local.  Contains a pointer to `struct TEH_KeyStateHandle` or NULL.
- * Stores the per-thread latest generation of our key state.
+ * Stores the latest generation of our key state.
  */
-static pthread_key_t key_state;
+static struct TEH_KeyStateHandle *key_state;
 
 /**
  * Counter incremented whenever we have a reason to re-build the keys because
@@ -351,7 +349,7 @@ static pthread_key_t key_state;
  * changes, the variable MUST be volatile.  See #TEH_keys_get_state() and
  * #TEH_keys_update_states() for uses of this variable.
  */
-static volatile uint64_t key_generation;
+static uint64_t key_generation;
 
 /**
  * Head of DLL of suspended /keys requests.
@@ -392,29 +390,11 @@ static struct TALER_SecurityModulePublicKeyP denom_sm_pub;
 static struct TALER_SecurityModulePublicKeyP esign_sm_pub;
 
 /**
- * Mutex protecting access to #denom_sm_pub and #esign_sm_pub.
- * (Could be split into two locks if ever needed.)
- */
-static pthread_mutex_t sm_pub_mutex = PTHREAD_MUTEX_INITIALIZER;
-
-/**
- * Mutex protecting access to #skr_head and #skr_tail.
- * (Could be split into two locks if ever needed.)
- */
-static pthread_mutex_t skr_mutex = PTHREAD_MUTEX_INITIALIZER;
-
-/**
  * Are we shutting down?
  */
 static bool terminating;
 
 /**
- * Did we ever initialize #key_state?
- */
-static bool key_state_available;
-
-
-/**
  * Suspend /keys request while we (hopefully) are waiting to be
  * provisioned with key material.
  *
@@ -427,10 +407,8 @@ suspend_request (struct MHD_Connection *connection)
 
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
               "Suspending /keys request until key material changes\n");
-  GNUNET_assert (0 == pthread_mutex_lock (&skr_mutex));
   if (terminating)
   {
-    GNUNET_assert (0 == pthread_mutex_unlock (&skr_mutex));
     return TALER_MHD_reply_with_error (connection,
                                        MHD_HTTP_INTERNAL_SERVER_ERROR,
                                        TALER_EC_EXCHANGE_GENERIC_KEYS_MISSING,
@@ -452,9 +430,9 @@ suspend_request (struct MHD_Connection *connection)
     skr_size--;
     skr_connection = skr->connection;
     MHD_resume_connection (skr->connection);
+    TALER_MHD_daemon_trigger ();
     GNUNET_free (skr);
   }
-  GNUNET_assert (0 == pthread_mutex_unlock (&skr_mutex));
   return MHD_YES;
 }
 
@@ -464,7 +442,6 @@ TEH_resume_keys_requests (bool do_shutdown)
 {
   struct SuspendedKeysRequests *skr;
 
-  GNUNET_assert (0 == pthread_mutex_lock (&skr_mutex));
   if (do_shutdown)
     terminating = true;
   while (NULL != (skr = skr_head))
@@ -474,9 +451,9 @@ TEH_resume_keys_requests (bool do_shutdown)
                                  skr);
     skr_size--;
     MHD_resume_connection (skr->connection);
+    TALER_MHD_daemon_trigger ();
     GNUNET_free (skr);
   }
-  GNUNET_assert (0 == pthread_mutex_unlock (&skr_mutex));
 }
 
 
@@ -510,7 +487,6 @@ clear_response_cache (struct TEH_KeyStateHandle *ksh)
 static void
 check_denom_sm_pub (const struct TALER_SecurityModulePublicKeyP *sm_pub)
 {
-  GNUNET_assert (0 == pthread_mutex_lock (&sm_pub_mutex));
   if (0 !=
       GNUNET_memcmp (sm_pub,
                      &denom_sm_pub))
@@ -523,7 +499,6 @@ check_denom_sm_pub (const struct TALER_SecurityModulePublicKeyP *sm_pub)
     }
     denom_sm_pub = *sm_pub; /* TOFU ;-) */
   }
-  GNUNET_assert (0 == pthread_mutex_unlock (&sm_pub_mutex));
 }
 
 
@@ -536,7 +511,6 @@ check_denom_sm_pub (const struct TALER_SecurityModulePublicKeyP *sm_pub)
 static void
 check_esign_sm_pub (const struct TALER_SecurityModulePublicKeyP *sm_pub)
 {
-  GNUNET_assert (0 == pthread_mutex_lock (&sm_pub_mutex));
   if (0 !=
       GNUNET_memcmp (sm_pub,
                      &esign_sm_pub))
@@ -549,7 +523,6 @@ check_esign_sm_pub (const struct TALER_SecurityModulePublicKeyP *sm_pub)
     }
     esign_sm_pub = *sm_pub; /* TOFU ;-) */
   }
-  GNUNET_assert (0 == pthread_mutex_unlock (&sm_pub_mutex));
 }
 
 
@@ -896,38 +869,9 @@ destroy_key_state (struct TEH_KeyStateHandle *ksh,
 }
 
 
-/**
- * Free all resources associated with @a cls.  Called when
- * the respective pthread is destroyed.
- *
- * @param[in] cls a `struct TEH_KeyStateHandle`.
- */
-static void
-destroy_key_state_cb (void *cls)
-{
-  struct TEH_KeyStateHandle *ksh = cls;
-
-  destroy_key_state (ksh,
-                     true);
-}
-
-
-/**
- * Initialize keys submodule.
- *
- * @return #GNUNET_OK on success
- */
 int
 TEH_keys_init ()
 {
-  if (0 !=
-      pthread_key_create (&key_state,
-                          &destroy_key_state_cb))
-  {
-    GNUNET_break (0);
-    return GNUNET_SYSERR;
-  }
-  key_state_available = true;
   if (GNUNET_OK !=
       GNUNET_CONFIGURATION_get_value_time (TEH_cfg,
                                            "exchange",
@@ -949,11 +893,9 @@ TEH_keys_init ()
 void __attribute__ ((destructor))
 TEH_keys_finished ()
 {
-  if (key_state_available)
-  {
-    GNUNET_assert (0 ==
-                   pthread_key_delete (key_state));
-  }
+  if (NULL != key_state)
+    destroy_key_state (key_state,
+                       true);
 }
 
 
@@ -1799,22 +1741,14 @@ get_key_state (bool management_only)
   struct TEH_KeyStateHandle *old_ksh;
   struct TEH_KeyStateHandle *ksh;
 
-  GNUNET_assert (key_state_available);
-  old_ksh = pthread_getspecific (key_state);
+  old_ksh = key_state;
   if (NULL == old_ksh)
   {
     ksh = build_key_state (NULL,
                            management_only);
     if (NULL == ksh)
       return NULL;
-    if (0 != pthread_setspecific (key_state,
-                                  ksh))
-    {
-      GNUNET_break (0);
-      destroy_key_state (ksh,
-                         true);
-      return NULL;
-    }
+    key_state = ksh;
     return ksh;
   }
   if ( (old_ksh->key_generation < key_generation) ||
@@ -1826,15 +1760,7 @@ get_key_state (bool management_only)
                 (unsigned long long) key_generation);
     ksh = build_key_state (old_ksh->helpers,
                            management_only);
-    if (0 != pthread_setspecific (key_state,
-                                  ksh))
-    {
-      GNUNET_break (0);
-      if (NULL != ksh)
-        destroy_key_state (ksh,
-                           false);
-      return NULL;
-    }
+    key_state = ksh;
     old_ksh->helpers = NULL;
     destroy_key_state (old_ksh,
                        false);
@@ -2099,17 +2025,14 @@ TEH_keys_get_handler (struct TEH_RequestContext *rc,
     ksh = TEH_keys_get_state ();
     if (NULL == ksh)
     {
-      GNUNET_assert (0 == pthread_mutex_lock (&skr_mutex));
       if ( (SKR_LIMIT == skr_size) &&
            (rc->connection == skr_connection) )
       {
-        GNUNET_assert (0 == pthread_mutex_unlock (&skr_mutex));
         return TALER_MHD_reply_with_error (rc->connection,
                                            MHD_HTTP_INTERNAL_SERVER_ERROR,
                                            TALER_EC_EXCHANGE_GENERIC_KEYS_MISSING,
                                            "too many connections suspended on /keys");
       }
-      GNUNET_assert (0 == pthread_mutex_unlock (&skr_mutex));
       return suspend_request (rc->connection);
     }
     krd = bsearch (&last_issue_date,
diff --git a/src/exchange/taler-exchange-httpd_link.c b/src/exchange/taler-exchange-httpd_link.c
index bbb027522..75d32e562 100644
--- a/src/exchange/taler-exchange-httpd_link.c
+++ b/src/exchange/taler-exchange-httpd_link.c
@@ -130,7 +130,6 @@ fail:
  *
  * @param cls closure
  * @param connection MHD request which triggered the transaction
- * @param session database session to use
  * @param[out] mhd_ret set to MHD response status for @a connection,
  *             if transaction failed (!)
  * @return transaction status
@@ -138,14 +137,12 @@ fail:
 static enum GNUNET_DB_QueryStatus
 link_transaction (void *cls,
                   struct MHD_Connection *connection,
-                  struct TALER_EXCHANGEDB_Session *session,
                   MHD_RESULT *mhd_ret)
 {
   struct HTD_Context *ctx = cls;
   enum GNUNET_DB_QueryStatus qs;
 
   qs = TEH_plugin->get_link_data (TEH_plugin->cls,
-                                  session,
                                   &ctx->coin_pub,
                                   &handle_link_data,
                                   ctx);
diff --git a/src/exchange/taler-exchange-httpd_loop.c b/src/exchange/taler-exchange-httpd_loop.c
deleted file mode 100644
index 086fbc874..000000000
--- a/src/exchange/taler-exchange-httpd_loop.c
+++ /dev/null
@@ -1,209 +0,0 @@
-/*
-  This file is part of TALER
-  Copyright (C) 2014--2020 Taler Systems SA
-
-  TALER is free software; you can redistribute it and/or modify it under the
-  terms of the GNU Affero General Public License as published by the Free Software
-  Foundation; either version 3, or (at your option) any later version.
-
-  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
-  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
-  A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more details.
-
-  You should have received a copy of the GNU Affero General Public License along with
-  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
-*/
-/**
- * @file taler-exchange-httpd_loop.c
- * @brief management of our main loop
- * @author Florian Dold
- * @author Benedikt Mueller
- * @author Christian Grothoff
- */
-#include "platform.h"
-#include <pthread.h>
-#include "taler-exchange-httpd_loop.h"
-
-
-/* ************************* Signal logic ************************** */
-
-/**
- * Pipe used for signaling reloading of our key state.
- */
-static int reload_pipe[2] = { -1, -1 };
-
-
-/**
- * Handle a signal, writing relevant signal numbers to the pipe.
- *
- * @param signal_number the signal number
- */
-static void
-handle_signal (int signal_number)
-{
-  char c = (char) signal_number; /* never seen a signal_number > 127 on any platform */
-
-  (void) ! write (reload_pipe[1],
-                  &c,
-                  1);
-  /* While one might like to "handle errors" here, even logging via fprintf()
-     isn't safe inside of a signal handler. So there is nothing we safely CAN
-     do. OTOH, also very little that can go wrong in practice. Calling _exit()
-     on errors might be a possibility, but that might do more harm than good. *///
-}
-
-
-/**
- * Call #handle_signal() to pass the received signal via
- * the control pipe.
- */
-static void
-handle_sigint (void)
-{
-  handle_signal (SIGINT);
-}
-
-
-/**
- * Call #handle_signal() to pass the received signal via
- * the control pipe.
- */
-static void
-handle_sigterm (void)
-{
-  handle_signal (SIGTERM);
-}
-
-
-/**
- * Call #handle_signal() to pass the received signal via
- * the control pipe.
- */
-static void
-handle_sighup (void)
-{
-  handle_signal (SIGHUP);
-}
-
-
-/**
- * Call #handle_signal() to pass the received signal via
- * the control pipe.
- */
-static void
-handle_sigchld (void)
-{
-  handle_signal (SIGCHLD);
-}
-
-
-int
-TEH_loop_run (void)
-{
-  int ret;
-
-  ret = 2;
-  while (2 == ret)
-  {
-    char c;
-    ssize_t res;
-
-    errno = 0;
-    res = read (reload_pipe[0],
-                &c,
-                1);
-    if ((res < 0) && (EINTR != errno))
-    {
-      GNUNET_break (0);
-      ret = GNUNET_SYSERR;
-      break;
-    }
-    if (EINTR == errno)
-      continue;
-    switch (c)
-    {
-    case SIGTERM:
-    case SIGINT:
-      /* terminate */
-      ret = GNUNET_OK;
-      break;
-    case SIGHUP:
-      /* restart updated binary */
-      ret = GNUNET_NO;
-      break;
-#if HAVE_DEVELOPER
-    case SIGCHLD:
-      /* running in test-mode, test finished, terminate */
-      ret = GNUNET_OK;
-      break;
-#endif
-    default:
-      /* unexpected character */
-      GNUNET_break (0);
-      break;
-    }
-  }
-  return ret;
-}
-
-
-static struct GNUNET_SIGNAL_Context *sigterm;
-static struct GNUNET_SIGNAL_Context *sigint;
-static struct GNUNET_SIGNAL_Context *sighup;
-static struct GNUNET_SIGNAL_Context *sigchld;
-
-
-int
-TEH_loop_init (void)
-{
-  if (0 != pipe (reload_pipe))
-  {
-    GNUNET_log_strerror (GNUNET_ERROR_TYPE_ERROR,
-                         "pipe");
-    return GNUNET_SYSERR;
-  }
-  sigterm = GNUNET_SIGNAL_handler_install (SIGTERM,
-                                           &handle_sigterm);
-  sigint = GNUNET_SIGNAL_handler_install (SIGINT,
-                                          &handle_sigint);
-  sighup = GNUNET_SIGNAL_handler_install (SIGHUP,
-                                          &handle_sighup);
-  sigchld = GNUNET_SIGNAL_handler_install (SIGCHLD,
-                                           &handle_sigchld);
-  return GNUNET_OK;
-}
-
-
-void
-TEH_loop_done (void)
-{
-  if (NULL != sigterm)
-  {
-    GNUNET_SIGNAL_handler_uninstall (sigterm);
-    sigterm = NULL;
-  }
-  if (NULL != sigint)
-  {
-    GNUNET_SIGNAL_handler_uninstall (sigint);
-    sigint = NULL;
-  }
-  if (NULL != sighup)
-  {
-    GNUNET_SIGNAL_handler_uninstall (sighup);
-    sighup = NULL;
-  }
-  if (NULL != sigchld)
-  {
-    GNUNET_SIGNAL_handler_uninstall (sigchld);
-    sigchld = NULL;
-  }
-  if (-1 != reload_pipe[0])
-  {
-    GNUNET_break (0 == close (reload_pipe[0]));
-    GNUNET_break (0 == close (reload_pipe[1]));
-    reload_pipe[0] = reload_pipe[1] = -1;
-  }
-}
-
-
-/* end of taler-exchange-httpd_loop.c */
diff --git a/src/exchange/taler-exchange-httpd_loop.h b/src/exchange/taler-exchange-httpd_loop.h
deleted file mode 100644
index 700f56776..000000000
--- a/src/exchange/taler-exchange-httpd_loop.h
+++ /dev/null
@@ -1,60 +0,0 @@
-/*
-  This file is part of TALER
-  Copyright (C) 2014, 2015 Taler Systems SA
-
-  TALER is free software; you can redistribute it and/or modify it under the
-  terms of the GNU Affero General Public License as published by the Free Software
-  Foundation; either version 3, or (at your option) any later version.
-
-  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
-  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
-  A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more details.
-
-  You should have received a copy of the GNU Affero General Public License along with
-  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
-*/
-/**
- * @file exchange/taler-exchange-httpd_loop.h
- * @brief management of our main loop
- * @author Florian Dold
- * @author Benedikt Mueller
- * @author Christian Grothoff
- */
-#ifndef TALER_EXCHANGE_HTTPD_LOOP_H
-#define TALER_EXCHANGE_HTTPD_LOOP_H
-
-#include <gnunet/gnunet_util_lib.h>
-#include <microhttpd.h>
-#include "taler-exchange-httpd.h"
-
-
-/**
- * Setup our signal handlers.
- *
- * @return #GNUNET_OK on success
- */
-int
-TEH_loop_init (void);
-
-
-/**
- * Finally, tear down our signal handlers.
- */
-void
-TEH_loop_done (void);
-
-
-/**
- * Read signals from a pipe in a loop, and reload keys from disk if
- * SIGUSR1 is received, terminate if SIGTERM/SIGINT is received, and
- * restart if SIGHUP is received.
- *
- * @return #GNUNET_SYSERR on errors,
- *         #GNUNET_OK to terminate normally
- *         #GNUNET_NO to restart an update version of the binary
- */
-int
-TEH_loop_run (void);
-
-
-#endif
diff --git a/src/exchange/taler-exchange-httpd_management_auditors.c b/src/exchange/taler-exchange-httpd_management_auditors.c
index 77e7d8657..d782618f1 100644
--- a/src/exchange/taler-exchange-httpd_management_auditors.c
+++ b/src/exchange/taler-exchange-httpd_management_auditors.c
@@ -74,7 +74,6 @@ struct AddAuditorContext
  *
  * @param cls closure with a `struct AddAuditorContext`
  * @param connection MHD request which triggered the transaction
- * @param session database session to use
  * @param[out] mhd_ret set to MHD response status for @a connection,
  *             if transaction failed (!)
  * @return transaction status
@@ -82,7 +81,6 @@ struct AddAuditorContext
 static enum GNUNET_DB_QueryStatus
 add_auditor (void *cls,
              struct MHD_Connection *connection,
-             struct TALER_EXCHANGEDB_Session *session,
              MHD_RESULT *mhd_ret)
 {
   struct AddAuditorContext *aac = cls;
@@ -90,7 +88,6 @@ add_auditor (void *cls,
   enum GNUNET_DB_QueryStatus qs;
 
   qs = TEH_plugin->lookup_auditor_timestamp (TEH_plugin->cls,
-                                             session,
                                              &aac->auditor_pub,
                                              &last_date);
   if (qs < 0)
@@ -116,14 +113,12 @@ add_auditor (void *cls,
   }
   if (0 == qs)
     qs = TEH_plugin->insert_auditor (TEH_plugin->cls,
-                                     session,
                                      &aac->auditor_pub,
                                      aac->auditor_url,
                                      aac->auditor_name,
                                      aac->validity_start);
   else
     qs = TEH_plugin->update_auditor (TEH_plugin->cls,
-                                     session,
                                      &aac->auditor_pub,
                                      aac->auditor_url,
                                      aac->auditor_name,
diff --git a/src/exchange/taler-exchange-httpd_management_auditors_AP_disable.c b/src/exchange/taler-exchange-httpd_management_auditors_AP_disable.c
index 382b0f6b4..7bf191f47 100644
--- a/src/exchange/taler-exchange-httpd_management_auditors_AP_disable.c
+++ b/src/exchange/taler-exchange-httpd_management_auditors_AP_disable.c
@@ -65,7 +65,6 @@ struct DelAuditorContext
  *
  * @param cls closure with a `struct DelAuditorContext`
  * @param connection MHD request which triggered the transaction
- * @param session database session to use
  * @param[out] mhd_ret set to MHD response status for @a connection,
  *             if transaction failed (!)
  * @return transaction status
@@ -73,7 +72,6 @@ struct DelAuditorContext
 static enum GNUNET_DB_QueryStatus
 del_auditor (void *cls,
              struct MHD_Connection *connection,
-             struct TALER_EXCHANGEDB_Session *session,
              MHD_RESULT *mhd_ret)
 {
   struct DelAuditorContext *dac = cls;
@@ -81,7 +79,6 @@ del_auditor (void *cls,
   enum GNUNET_DB_QueryStatus qs;
 
   qs = TEH_plugin->lookup_auditor_timestamp (TEH_plugin->cls,
-                                             session,
                                              &dac->auditor_pub,
                                              &last_date);
   if (qs < 0)
@@ -114,7 +111,6 @@ del_auditor (void *cls,
     return GNUNET_DB_STATUS_HARD_ERROR;
   }
   qs = TEH_plugin->update_auditor (TEH_plugin->cls,
-                                   session,
                                    &dac->auditor_pub,
                                    "", /* auditor URL */
                                    "", /* auditor name */
diff --git a/src/exchange/taler-exchange-httpd_management_denominations_HDP_revoke.c b/src/exchange/taler-exchange-httpd_management_denominations_HDP_revoke.c
index 1a89652e8..6519404df 100644
--- a/src/exchange/taler-exchange-httpd_management_denominations_HDP_revoke.c
+++ b/src/exchange/taler-exchange-httpd_management_denominations_HDP_revoke.c
@@ -70,7 +70,6 @@ TEH_handler_management_denominations_HDP_revoke (
       NULL);
   }
   qs = TEH_plugin->insert_denomination_revocation (TEH_plugin->cls,
-                                                   NULL,
                                                    h_denom_pub,
                                                    &master_sig);
   if (qs < 0)
diff --git a/src/exchange/taler-exchange-httpd_management_post_keys.c b/src/exchange/taler-exchange-httpd_management_post_keys.c
index 0e4eb9894..311fff781 100644
--- a/src/exchange/taler-exchange-httpd_management_post_keys.c
+++ b/src/exchange/taler-exchange-httpd_management_post_keys.c
@@ -107,7 +107,6 @@ struct AddKeysContext
  *
  * @param cls closure with a `struct AddKeysContext`
  * @param connection MHD request which triggered the transaction
- * @param session database session to use
  * @param[out] mhd_ret set to MHD response status for @a connection,
  *             if transaction failed (!)
  * @return transaction status
@@ -115,7 +114,6 @@ struct AddKeysContext
 static enum GNUNET_DB_QueryStatus
 add_keys (void *cls,
           struct MHD_Connection *connection,
-          struct TALER_EXCHANGEDB_Session *session,
           MHD_RESULT *mhd_ret)
 {
   struct AddKeysContext *akc = cls;
@@ -131,7 +129,6 @@ add_keys (void *cls,
     /* For idempotency, check if the key is already active */
     qs = TEH_plugin->lookup_denomination_key (
       TEH_plugin->cls,
-      session,
       &akc->d_sigs[i].h_denom_pub,
       &meta);
     if (qs < 0)
@@ -207,7 +204,6 @@ add_keys (void *cls,
       continue; /* skip, already known */
     qs = TEH_plugin->add_denomination_key (
       TEH_plugin->cls,
-      session,
       &akc->d_sigs[i].h_denom_pub,
       &denom_pub,
       &meta,
@@ -239,7 +235,6 @@ add_keys (void *cls,
 
     qs = TEH_plugin->lookup_signing_key (
       TEH_plugin->cls,
-      session,
       &akc->s_sigs[i].exchange_pub,
       &meta);
     if (qs < 0)
@@ -297,7 +292,6 @@ add_keys (void *cls,
       continue; /* skip, already known */
     qs = TEH_plugin->activate_signing_key (
       TEH_plugin->cls,
-      session,
       &akc->s_sigs[i].exchange_pub,
       &meta,
       &akc->s_sigs[i].master_sig);
diff --git a/src/exchange/taler-exchange-httpd_management_signkey_EP_revoke.c b/src/exchange/taler-exchange-httpd_management_signkey_EP_revoke.c
index 273c05d58..0d6317b47 100644
--- a/src/exchange/taler-exchange-httpd_management_signkey_EP_revoke.c
+++ b/src/exchange/taler-exchange-httpd_management_signkey_EP_revoke.c
@@ -69,7 +69,6 @@ TEH_handler_management_signkeys_EP_revoke (
       NULL);
   }
   qs = TEH_plugin->insert_signkey_revocation (TEH_plugin->cls,
-                                              NULL,
                                               exchange_pub,
                                               &master_sig);
   if (qs < 0)
diff --git a/src/exchange/taler-exchange-httpd_management_wire_disable.c b/src/exchange/taler-exchange-httpd_management_wire_disable.c
index 3b760ea9f..17bd7273f 100644
--- a/src/exchange/taler-exchange-httpd_management_wire_disable.c
+++ b/src/exchange/taler-exchange-httpd_management_wire_disable.c
@@ -65,7 +65,6 @@ struct DelWireContext
  *
  * @param cls closure with a `struct DelWireContext`
  * @param connection MHD request which triggered the transaction
- * @param session database session to use
  * @param[out] mhd_ret set to MHD response status for @a connection,
  *             if transaction failed (!)
  * @return transaction status
@@ -73,7 +72,6 @@ struct DelWireContext
 static enum GNUNET_DB_QueryStatus
 del_wire (void *cls,
           struct MHD_Connection *connection,
-          struct TALER_EXCHANGEDB_Session *session,
           MHD_RESULT *mhd_ret)
 {
   struct DelWireContext *awc = cls;
@@ -81,7 +79,6 @@ del_wire (void *cls,
   enum GNUNET_DB_QueryStatus qs;
 
   qs = TEH_plugin->lookup_wire_timestamp (TEH_plugin->cls,
-                                          session,
                                           awc->payto_uri,
                                           &last_date);
   if (qs < 0)
@@ -114,7 +111,6 @@ del_wire (void *cls,
     return GNUNET_DB_STATUS_HARD_ERROR;
   }
   qs = TEH_plugin->update_wire (TEH_plugin->cls,
-                                session,
                                 awc->payto_uri,
                                 awc->validity_end,
                                 false);
diff --git a/src/exchange/taler-exchange-httpd_management_wire_enable.c b/src/exchange/taler-exchange-httpd_management_wire_enable.c
index 00c95b05c..4bad41b40 100644
--- a/src/exchange/taler-exchange-httpd_management_wire_enable.c
+++ b/src/exchange/taler-exchange-httpd_management_wire_enable.c
@@ -72,7 +72,6 @@ struct AddWireContext
  *
  * @param cls closure with a `struct AddWireContext`
  * @param connection MHD request which triggered the transaction
- * @param session database session to use
  * @param[out] mhd_ret set to MHD response status for @a connection,
  *             if transaction failed (!)
  * @return transaction status
@@ -80,7 +79,6 @@ struct AddWireContext
 static enum GNUNET_DB_QueryStatus
 add_wire (void *cls,
           struct MHD_Connection *connection,
-          struct TALER_EXCHANGEDB_Session *session,
           MHD_RESULT *mhd_ret)
 {
   struct AddWireContext *awc = cls;
@@ -88,7 +86,6 @@ add_wire (void *cls,
   enum GNUNET_DB_QueryStatus qs;
 
   qs = TEH_plugin->lookup_wire_timestamp (TEH_plugin->cls,
-                                          session,
                                           awc->payto_uri,
                                           &last_date);
   if (qs < 0)
@@ -114,13 +111,11 @@ add_wire (void *cls,
   }
   if (0 == qs)
     qs = TEH_plugin->insert_wire (TEH_plugin->cls,
-                                  session,
                                   awc->payto_uri,
                                   awc->validity_start,
                                   &awc->master_sig_wire);
   else
     qs = TEH_plugin->update_wire (TEH_plugin->cls,
-                                  session,
                                   awc->payto_uri,
                                   awc->validity_start,
                                   true);
diff --git a/src/exchange/taler-exchange-httpd_management_wire_fees.c b/src/exchange/taler-exchange-httpd_management_wire_fees.c
index 5486ff336..4272a2d06 100644
--- a/src/exchange/taler-exchange-httpd_management_wire_fees.c
+++ b/src/exchange/taler-exchange-httpd_management_wire_fees.c
@@ -80,7 +80,6 @@ struct AddFeeContext
  *
  * @param cls closure with a `struct AddFeeContext`
  * @param connection MHD request which triggered the transaction
- * @param session database session to use
  * @param[out] mhd_ret set to MHD response status for @a connection,
  *             if transaction failed (!)
  * @return transaction status
@@ -88,7 +87,6 @@ struct AddFeeContext
 static enum GNUNET_DB_QueryStatus
 add_fee (void *cls,
          struct MHD_Connection *connection,
-         struct TALER_EXCHANGEDB_Session *session,
          MHD_RESULT *mhd_ret)
 {
   struct AddFeeContext *afc = cls;
@@ -98,7 +96,6 @@ add_fee (void *cls,
 
   qs = TEH_plugin->lookup_wire_fee_by_time (
     TEH_plugin->cls,
-    session,
     afc->wire_method,
     afc->start_time,
     afc->end_time,
@@ -142,7 +139,6 @@ add_fee (void *cls,
 
   qs = TEH_plugin->insert_wire_fee (
     TEH_plugin->cls,
-    session,
     afc->wire_method,
     afc->start_time,
     afc->end_time,
diff --git a/src/exchange/taler-exchange-httpd_melt.c b/src/exchange/taler-exchange-httpd_melt.c
index 071a9c380..af0a0a636 100644
--- a/src/exchange/taler-exchange-httpd_melt.c
+++ b/src/exchange/taler-exchange-httpd_melt.c
@@ -170,14 +170,12 @@ struct MeltContext
  * melt operation.
  *
  * @param connection the connection to send errors to
- * @param session the database connection
  * @param[in,out] rmc melt context
  * @param[out] mhd_ret status code to return to MHD on hard error
  * @return transaction status code
  */
 static enum GNUNET_DB_QueryStatus
 refresh_check_melt (struct MHD_Connection *connection,
-                    struct TALER_EXCHANGEDB_Session *session,
                     struct MeltContext *rmc,
                     MHD_RESULT *mhd_ret)
 {
@@ -191,7 +189,6 @@ refresh_check_melt (struct MHD_Connection *connection,
   /* get historic transaction costs of this coin, including recoups as
      we might be a zombie coin */
   qs = TEH_plugin->get_coin_transactions (TEH_plugin->cls,
-                                          session,
                                           &rmc->refresh_session.coin.coin_pub,
                                           GNUNET_YES,
                                           &tl);
@@ -301,7 +298,6 @@ refresh_check_melt (struct MHD_Connection *connection,
  *
  * @param cls our `struct MeltContext`
  * @param connection MHD request which triggered the transaction
- * @param session database session to use
  * @param[out] mhd_ret set to MHD response status for @a connection,
  *             if transaction failed (!)
  * @return transaction status
@@ -309,7 +305,6 @@ refresh_check_melt (struct MHD_Connection *connection,
 static enum GNUNET_DB_QueryStatus
 melt_transaction (void *cls,
                   struct MHD_Connection *connection,
-                  struct TALER_EXCHANGEDB_Session *session,
                   MHD_RESULT *mhd_ret)
 {
   struct MeltContext *rmc = cls;
@@ -321,7 +316,6 @@ melt_transaction (void *cls,
   {
     qs = TEH_make_coin_known (&rmc->refresh_session.coin,
                               connection,
-                              session,
                               mhd_ret);
     if (qs < 0)
       return qs;
@@ -329,7 +323,6 @@ melt_transaction (void *cls,
 
   /* Check if we already created a matching refresh_session */
   qs = TEH_plugin->get_melt_index (TEH_plugin->cls,
-                                   session,
                                    &rmc->refresh_session.rc,
                                    &noreveal_index);
   if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT == qs)
@@ -355,7 +348,6 @@ melt_transaction (void *cls,
 
   /* check coin has enough funds remaining on it to cover melt cost */
   qs = refresh_check_melt (connection,
-                           session,
                            rmc,
                            mhd_ret);
   if (0 > qs)
@@ -367,7 +359,6 @@ melt_transaction (void *cls,
                                 TALER_CNC_KAPPA);
   if (0 >=
       (qs = TEH_plugin->insert_melt (TEH_plugin->cls,
-                                     session,
                                      &rmc->refresh_session)))
   {
     if (GNUNET_DB_STATUS_SOFT_ERROR != qs)
@@ -511,7 +502,6 @@ check_for_denomination_key (struct MHD_Connection *connection,
        revoked (those must be recouped) */
     qs = TEH_plugin->get_coin_denomination (
       TEH_plugin->cls,
-      NULL,
       &rmc->refresh_session.coin.coin_pub,
       &denom_hash);
     if (0 > qs)
diff --git a/src/exchange/taler-exchange-httpd_recoup.c b/src/exchange/taler-exchange-httpd_recoup.c
index 521b75627..137034a42 100644
--- a/src/exchange/taler-exchange-httpd_recoup.c
+++ b/src/exchange/taler-exchange-httpd_recoup.c
@@ -114,7 +114,6 @@ struct RecoupContext
  *
  * @param cls the `struct RecoupContext *`
  * @param connection MHD request which triggered the transaction
- * @param session database session to use
  * @param[out] mhd_ret set to MHD response status for @a connection,
  *             if transaction failed (!)
  * @return transaction status code
@@ -122,7 +121,6 @@ struct RecoupContext
 static enum GNUNET_DB_QueryStatus
 recoup_transaction (void *cls,
                     struct MHD_Connection *connection,
-                    struct TALER_EXCHANGEDB_Session *session,
                     MHD_RESULT *mhd_ret)
 {
   struct RecoupContext *pc = cls;
@@ -135,7 +133,6 @@ recoup_transaction (void *cls,
   /* make sure coin is 'known' in database */
   qs = TEH_make_coin_known (pc->coin,
                             connection,
-                            session,
                             mhd_ret);
   if (qs < 0)
     return qs;
@@ -145,7 +142,6 @@ recoup_transaction (void *cls,
   if (pc->refreshed)
   {
     qs = TEH_plugin->get_old_coin_by_h_blind (TEH_plugin->cls,
-                                              session,
                                               &pc->h_blind,
                                               &pc->target.old_coin_pub);
     if (0 > qs)
@@ -164,7 +160,6 @@ recoup_transaction (void *cls,
   else
   {
     qs = TEH_plugin->get_reserve_by_h_blind (TEH_plugin->cls,
-                                             session,
                                              &pc->h_blind,
                                              &pc->target.reserve_pub);
     if (0 > qs)
@@ -194,7 +189,6 @@ recoup_transaction (void *cls,
 
   /* Calculate remaining balance, including recoups already applied. */
   qs = TEH_plugin->get_coin_transactions (TEH_plugin->cls,
-                                          session,
                                           &pc->coin->coin_pub,
                                           GNUNET_YES,
                                           &tl);
@@ -270,8 +264,7 @@ recoup_transaction (void *cls,
     /* Recoup has no effect: coin fully spent! */
     enum GNUNET_DB_QueryStatus ret;
 
-    TEH_plugin->rollback (TEH_plugin->cls,
-                          session);
+    TEH_plugin->rollback (TEH_plugin->cls);
     if (GNUNET_NO == existing_recoup_found)
     {
       /* Refuse: insufficient funds for recoup */
@@ -300,7 +293,6 @@ recoup_transaction (void *cls,
   if (pc->refreshed)
   {
     qs = TEH_plugin->insert_recoup_refresh_request (TEH_plugin->cls,
-                                                    session,
                                                     pc->coin,
                                                     pc->coin_sig,
                                                     pc->coin_bks,
@@ -311,7 +303,6 @@ recoup_transaction (void *cls,
   else
   {
     qs = TEH_plugin->insert_recoup_request (TEH_plugin->cls,
-                                            session,
                                             &pc->target.reserve_pub,
                                             pc->coin,
                                             pc->coin_sig,
diff --git a/src/exchange/taler-exchange-httpd_refreshes_reveal.c b/src/exchange/taler-exchange-httpd_refreshes_reveal.c
index dc4bdf0e6..4ca6bd15b 100644
--- a/src/exchange/taler-exchange-httpd_refreshes_reveal.c
+++ b/src/exchange/taler-exchange-httpd_refreshes_reveal.c
@@ -201,7 +201,6 @@ check_exists_cb (void *cls,
  *
  * @param cls closure of type `struct RevealContext`
  * @param connection MHD request which triggered the transaction
- * @param session database session to use
  * @param[out] mhd_ret set to MHD response status for @a connection,
  *             if transaction failed (!)
  * @return transaction status
@@ -209,7 +208,6 @@ check_exists_cb (void *cls,
 static enum GNUNET_DB_QueryStatus
 refreshes_reveal_preflight (void *cls,
                             struct MHD_Connection *connection,
-                            struct TALER_EXCHANGEDB_Session *session,
                             MHD_RESULT *mhd_ret)
 {
   struct RevealContext *rctx = cls;
@@ -217,7 +215,6 @@ refreshes_reveal_preflight (void *cls,
 
   /* Try to see if we already have given an answer before. */
   qs = TEH_plugin->get_refresh_reveal (TEH_plugin->cls,
-                                       session,
                                        &rctx->rc,
                                        &check_exists_cb,
                                        rctx);
@@ -258,7 +255,6 @@ refreshes_reveal_preflight (void *cls,
  *
  * @param cls closure of type `struct RevealContext`
  * @param connection MHD request which triggered the transaction
- * @param session database session to use
  * @param[out] mhd_ret set to MHD response status for @a connection,
  *             if transaction failed (!)
  * @return transaction status
@@ -266,7 +262,6 @@ refreshes_reveal_preflight (void *cls,
 static enum GNUNET_DB_QueryStatus
 refreshes_reveal_transaction (void *cls,
                               struct MHD_Connection *connection,
-                              struct TALER_EXCHANGEDB_Session *session,
                               MHD_RESULT *mhd_ret)
 {
   struct RevealContext *rctx = cls;
@@ -276,7 +271,6 @@ refreshes_reveal_transaction (void *cls,
   /* Obtain basic information about the refresh operation and what
      gamma we committed to. */
   qs = TEH_plugin->get_melt (TEH_plugin->cls,
-                             session,
                              &rctx->rc,
                              &melt);
   if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
@@ -441,7 +435,6 @@ refreshes_reveal_transaction (void *cls,
  *
  * @param cls closure of type `struct RevealContext`
  * @param connection MHD request which triggered the transaction
- * @param session database session to use
  * @param[out] mhd_ret set to MHD response status for @a connection,
  *             if transaction failed (!)
  * @return transaction status
@@ -449,7 +442,6 @@ refreshes_reveal_transaction (void *cls,
 static enum GNUNET_DB_QueryStatus
 refreshes_reveal_persist (void *cls,
                           struct MHD_Connection *connection,
-                          struct TALER_EXCHANGEDB_Session *session,
                           MHD_RESULT *mhd_ret)
 {
   struct RevealContext *rctx = cls;
@@ -470,7 +462,6 @@ refreshes_reveal_persist (void *cls,
       rrc->coin_sig = rctx->ev_sigs[i];
     }
     qs = TEH_plugin->insert_refresh_reveal (TEH_plugin->cls,
-                                            session,
                                             &rctx->rc,
                                             rctx->num_fresh_coins,
                                             rrcs,
@@ -621,7 +612,6 @@ resolve_refreshes_reveal_denominations (struct MHD_Connection *connection,
 
     if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT !=
         (qs = TEH_plugin->get_melt (TEH_plugin->cls,
-                                    NULL,
                                     &rctx->rc,
                                     &melt)))
     {
diff --git a/src/exchange/taler-exchange-httpd_refund.c b/src/exchange/taler-exchange-httpd_refund.c
index 2ea19b7e8..73b4b251b 100644
--- a/src/exchange/taler-exchange-httpd_refund.c
+++ b/src/exchange/taler-exchange-httpd_refund.c
@@ -94,7 +94,6 @@ reply_refund_success (struct MHD_Connection *connection,
  *
  * @param cls closure with a `const struct TALER_EXCHANGEDB_Refund *`
  * @param connection MHD request which triggered the transaction
- * @param session database session to use
  * @param[out] mhd_ret set to MHD response status for @a connection,
  *             if transaction failed (!)
  * @return transaction status
@@ -102,7 +101,6 @@ reply_refund_success (struct MHD_Connection *connection,
 static enum GNUNET_DB_QueryStatus
 refund_transaction (void *cls,
                     struct MHD_Connection *connection,
-                    struct TALER_EXCHANGEDB_Session *session,
                     MHD_RESULT *mhd_ret)
 {
   const struct TALER_EXCHANGEDB_Refund *refund = cls;
@@ -118,7 +116,6 @@ refund_transaction (void *cls,
 
   tl = NULL;
   qs = TEH_plugin->get_coin_transactions (TEH_plugin->cls,
-                                          session,
                                           &refund->coin.coin_pub,
                                           GNUNET_NO,
                                           &tl);
@@ -344,7 +341,6 @@ refund_transaction (void *cls,
 
   /* Finally, store new refund data */
   qs = TEH_plugin->insert_refund (TEH_plugin->cls,
-                                  session,
                                   refund);
   if (GNUNET_DB_STATUS_HARD_ERROR == qs)
   {
@@ -407,7 +403,6 @@ verify_and_execute_refund (struct MHD_Connection *connection,
     enum GNUNET_DB_QueryStatus qs;
 
     qs = TEH_plugin->get_coin_denomination (TEH_plugin->cls,
-                                            NULL,
                                             &refund->coin.coin_pub,
                                             &denom_hash);
     if (0 > qs)
diff --git a/src/exchange/taler-exchange-httpd_reserves_get.c b/src/exchange/taler-exchange-httpd_reserves_get.c
index 04085a0c3..57ab71378 100644
--- a/src/exchange/taler-exchange-httpd_reserves_get.c
+++ b/src/exchange/taler-exchange-httpd_reserves_get.c
@@ -54,7 +54,7 @@ struct ReservePoller
    * Subscription for the database event we are
    * waiting for.
    */
-  struct TALER_EXCHANGEDB_EventHandler *eh;
+  struct GNUNET_DB_EventHandler *eh;
 
   /**
    * When will this request time out?
@@ -110,8 +110,11 @@ rp_cleanup (struct TEH_RequestContext *rc)
 {
   struct ReservePoller *rp = rc->rh_ctx;
 
+  GNUNET_assert (! rp->suspended);
   if (NULL != rp->eh)
   {
+    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+                "Cancelling DB event listening\n");
     TEH_plugin->event_listen_cancel (TEH_plugin->cls,
                                      rp->eh);
     rp->eh = NULL;
@@ -153,6 +156,7 @@ db_event_cb (void *cls,
                                rp_tail,
                                rp);
   MHD_resume_connection (rp->connection);
+  TALER_MHD_daemon_trigger ();
   GNUNET_async_scope_restore (&old_scope);
 }
 
@@ -218,7 +222,6 @@ struct ReserveHistoryContext
  *
  * @param cls a `struct ReserveHistoryContext *`
  * @param connection MHD request which triggered the transaction
- * @param session database session to use
  * @param[out] mhd_ret set to MHD response status for @a connection,
  *             if transaction failed (!); unused
  * @return transaction status
@@ -226,7 +229,6 @@ struct ReserveHistoryContext
 static enum GNUNET_DB_QueryStatus
 reserve_history_transaction (void *cls,
                              struct MHD_Connection *connection,
-                             struct TALER_EXCHANGEDB_Session *session,
                              MHD_RESULT *mhd_ret)
 {
   struct ReserveHistoryContext *rsc = cls;
@@ -234,7 +236,6 @@ reserve_history_transaction (void *cls,
   (void) connection;
   (void) mhd_ret;
   return TEH_plugin->get_reserve_history (TEH_plugin->cls,
-                                          session,
                                           &rsc->reserve_pub,
                                           &rsc->rh);
 }
@@ -247,7 +248,7 @@ TEH_handler_reserves_get (struct TEH_RequestContext *rc,
   struct ReserveHistoryContext rsc;
   MHD_RESULT mhd_ret;
   struct GNUNET_TIME_Relative timeout = GNUNET_TIME_UNIT_ZERO;
-  struct TALER_EXCHANGEDB_EventHandler *eh = NULL;
+  struct GNUNET_DB_EventHandler *eh = NULL;
 
   if (GNUNET_OK !=
       GNUNET_STRINGS_string_to_data (args[0],
@@ -288,7 +289,8 @@ TEH_handler_reserves_get (struct TEH_RequestContext *rc,
                                                timeout_ms);
     }
   }
-  if (! GNUNET_TIME_relative_is_zero (timeout))
+  if ( (! GNUNET_TIME_relative_is_zero (timeout)) &&
+       (NULL == rc->rh_ctx) )
   {
     struct TALER_ReserveEventP rep = {
       .header.size = htons (sizeof (rep)),
@@ -296,6 +298,8 @@ TEH_handler_reserves_get (struct TEH_RequestContext *rc,
       .reserve_pub = rsc.reserve_pub
     };
 
+    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+                "Starting DB event listening\n");
     eh = TEH_plugin->event_listen (TEH_plugin->cls,
                                    timeout,
                                    &rep.header,
@@ -309,7 +313,12 @@ TEH_handler_reserves_get (struct TEH_RequestContext *rc,
                               &mhd_ret,
                               &reserve_history_transaction,
                               &rsc))
+  {
+    if (NULL != eh)
+      TEH_plugin->event_listen_cancel (TEH_plugin->cls,
+                                       eh);
     return mhd_ret;
+  }
   /* generate proper response */
   if (NULL == rsc.rh)
   {
@@ -340,6 +349,9 @@ TEH_handler_reserves_get (struct TEH_RequestContext *rc,
     MHD_suspend_connection (rc->connection);
     return MHD_YES;
   }
+  if (NULL != eh)
+    TEH_plugin->event_listen_cancel (TEH_plugin->cls,
+                                     eh);
   mhd_ret = reply_reserve_history_success (rc->connection,
                                            rsc.rh);
   TEH_plugin->free_reserve_history (TEH_plugin->cls,
diff --git a/src/exchange/taler-exchange-httpd_transfers_get.c b/src/exchange/taler-exchange-httpd_transfers_get.c
index 9fd343a53..abf0fdbc8 100644
--- a/src/exchange/taler-exchange-httpd_transfers_get.c
+++ b/src/exchange/taler-exchange-httpd_transfers_get.c
@@ -406,7 +406,6 @@ free_ctx (struct WtidTransactionContext *ctx)
  *
  * @param cls closure
  * @param connection MHD request which triggered the transaction
- * @param session database session to use
  * @param[out] mhd_ret set to MHD response status for @a connection,
  *             if transaction failed (!)
  * @return transaction status
@@ -414,7 +413,6 @@ free_ctx (struct WtidTransactionContext *ctx)
 static enum GNUNET_DB_QueryStatus
 get_transfer_deposits (void *cls,
                        struct MHD_Connection *connection,
-                       struct TALER_EXCHANGEDB_Session *session,
                        MHD_RESULT *mhd_ret)
 {
   struct WtidTransactionContext *ctx = cls;
@@ -428,7 +426,6 @@ get_transfer_deposits (void *cls,
      serialization failure */
   free_ctx (ctx);
   qs = TEH_plugin->lookup_wire_transfer (TEH_plugin->cls,
-                                         session,
                                          &ctx->wtid,
                                          &handle_deposit_data,
                                          ctx);
@@ -462,7 +459,6 @@ get_transfer_deposits (void *cls,
     return GNUNET_DB_STATUS_HARD_ERROR;
   }
   qs = TEH_plugin->get_wire_fee (TEH_plugin->cls,
-                                 session,
                                  ctx->wire_method,
                                  ctx->exec_time,
                                  &wire_fee_start_date,
diff --git a/src/exchange/taler-exchange-httpd_withdraw.c b/src/exchange/taler-exchange-httpd_withdraw.c
index 7d10bb8e7..d9cba045c 100644
--- a/src/exchange/taler-exchange-httpd_withdraw.c
+++ b/src/exchange/taler-exchange-httpd_withdraw.c
@@ -152,7 +152,6 @@ struct WithdrawContext
  *
  * @param cls a `struct WithdrawContext *`
  * @param connection MHD request which triggered the transaction
- * @param session database session to use
  * @param[out] mhd_ret set to MHD response status for @a connection,
  *             if transaction failed (!)
  * @return transaction status
@@ -160,7 +159,6 @@ struct WithdrawContext
 static enum GNUNET_DB_QueryStatus
 withdraw_transaction (void *cls,
                       struct MHD_Connection *connection,
-                      struct TALER_EXCHANGEDB_Session *session,
                       MHD_RESULT *mhd_ret)
 {
   struct WithdrawContext *wc = cls;
@@ -175,7 +173,6 @@ withdraw_transaction (void *cls,
   wc->collectable.sig.rsa_signature = NULL;
 #endif
   qs = TEH_plugin->get_withdraw_info (TEH_plugin->cls,
-                                      session,
                                       &wc->wsrd.h_coin_envelope,
                                       &wc->collectable);
   if (0 > qs)
@@ -212,7 +209,6 @@ withdraw_transaction (void *cls,
               "Trying to withdraw from reserve: %s\n",
               TALER_B2S (&r.pub));
   qs = TEH_plugin->reserves_get (TEH_plugin->cls,
-                                 session,
                                  &r);
   if (0 > qs)
   {
@@ -253,7 +249,6 @@ withdraw_transaction (void *cls,
     }
 #endif
     qs = TEH_plugin->get_reserve_history (TEH_plugin->cls,
-                                          session,
                                           &wc->wsrd.reserve_pub,
                                           &rh);
     if (NULL == rh)
@@ -300,7 +295,6 @@ withdraw_transaction (void *cls,
   wc->collectable.h_coin_envelope = wc->wsrd.h_coin_envelope;
   wc->collectable.reserve_sig = wc->signature;
   qs = TEH_plugin->insert_withdraw_info (TEH_plugin->cls,
-                                         session,
                                          &wc->collectable);
   if (0 > qs)
   {
diff --git a/src/exchange/taler-exchange-transfer.c b/src/exchange/taler-exchange-transfer.c
index 567943437..d6d44eb05 100644
--- a/src/exchange/taler-exchange-transfer.c
+++ b/src/exchange/taler-exchange-transfer.c
@@ -38,11 +38,6 @@ struct WirePrepareData
 {
 
   /**
-   * Database session for all of our transactions.
-   */
-  struct TALER_EXCHANGEDB_Session *session;
-
-  /**
    * Wire execution handle.
    */
   struct TALER_BANK_TransferHandle *eh;
@@ -140,8 +135,7 @@ shutdown_task (void *cls)
       TALER_BANK_transfer_cancel (wpd->eh);
       wpd->eh = NULL;
     }
-    db_plugin->rollback (db_plugin->cls,
-                         wpd->session);
+    db_plugin->rollback (db_plugin->cls);
     GNUNET_free (wpd);
     wpd = NULL;
   }
@@ -196,16 +190,14 @@ parse_wirewatch_config (void)
 /**
  * Perform a database commit. If it fails, print a warning.
  *
- * @param session session to perform the commit for.
  * @return status of commit
  */
 static enum GNUNET_DB_QueryStatus
-commit_or_warn (struct TALER_EXCHANGEDB_Session *session)
+commit_or_warn (void)
 {
   enum GNUNET_DB_QueryStatus qs;
 
-  qs = db_plugin->commit (db_plugin->cls,
-                          session);
+  qs = db_plugin->commit (db_plugin->cls);
   if (GNUNET_DB_STATUS_SUCCESS_NO_RESULTS == qs)
     return qs;
   GNUNET_log ((GNUNET_DB_STATUS_SOFT_ERROR == qs)
@@ -245,7 +237,6 @@ wire_confirm_cb (void *cls,
                  uint64_t row_id,
                  struct GNUNET_TIME_Absolute wire_timestamp)
 {
-  struct TALER_EXCHANGEDB_Session *session = wpd->session;
   enum GNUNET_DB_QueryStatus qs;
 
   (void) cls;
@@ -256,7 +247,6 @@ wire_confirm_cb (void *cls,
   {
   case MHD_HTTP_OK:
     qs = db_plugin->wire_prepare_data_mark_finished (db_plugin->cls,
-                                                     session,
                                                      wpd->row_id);
     /* continued below */
     break;
@@ -267,7 +257,6 @@ wire_confirm_cb (void *cls,
                 http_status_code,
                 ec);
     qs = db_plugin->wire_prepare_data_mark_failed (db_plugin->cls,
-                                                   session,
                                                    wpd->row_id);
     /* continued below */
     break;
@@ -276,8 +265,7 @@ wire_confirm_cb (void *cls,
                 "Wire transaction failed: %u/%d\n",
                 http_status_code,
                 ec);
-    db_plugin->rollback (db_plugin->cls,
-                         session);
+    db_plugin->rollback (db_plugin->cls);
     global_ret = EXIT_FAILURE;
     GNUNET_SCHEDULER_shutdown ();
     GNUNET_free (wpd);
@@ -287,8 +275,7 @@ wire_confirm_cb (void *cls,
   if (0 >= qs)
   {
     GNUNET_break (GNUNET_DB_STATUS_SOFT_ERROR == qs);
-    db_plugin->rollback (db_plugin->cls,
-                         session);
+    db_plugin->rollback (db_plugin->cls);
     if (GNUNET_DB_STATUS_SOFT_ERROR == qs)
     {
       /* try again */
@@ -307,7 +294,7 @@ wire_confirm_cb (void *cls,
   }
   GNUNET_free (wpd);
   wpd = NULL;
-  switch (commit_or_warn (session))
+  switch (commit_or_warn ())
   {
   case GNUNET_DB_STATUS_SOFT_ERROR:
     /* try again */
@@ -362,8 +349,7 @@ wire_prepare_cb (void *cls,
        (NULL == buf) )
   {
     GNUNET_break (0);
-    db_plugin->rollback (db_plugin->cls,
-                         wpd->session);
+    db_plugin->rollback (db_plugin->cls);
     global_ret = EXIT_FAILURE;
     goto cleanup;
   }
@@ -377,8 +363,7 @@ wire_prepare_cb (void *cls,
     /* Should really never happen here, as when we get
        here the wire account should be in the cache. */
     GNUNET_break (0);
-    db_plugin->rollback (db_plugin->cls,
-                         wpd->session);
+    db_plugin->rollback (db_plugin->cls);
     global_ret = EXIT_NOTCONFIGURED;
     goto cleanup;
   }
@@ -392,8 +377,7 @@ wire_prepare_cb (void *cls,
   if (NULL == wpd->eh)
   {
     GNUNET_break (0); /* Irrecoverable */
-    db_plugin->rollback (db_plugin->cls,
-                         wpd->session);
+    db_plugin->rollback (db_plugin->cls);
     global_ret = EXIT_FAILURE;
     goto cleanup;
   }
@@ -415,23 +399,22 @@ static void
 run_transfers (void *cls)
 {
   enum GNUNET_DB_QueryStatus qs;
-  struct TALER_EXCHANGEDB_Session *session;
 
   (void) cls;
   task = NULL;
   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
               "Checking for pending wire transfers\n");
-  if (NULL == (session = db_plugin->get_session (db_plugin->cls)))
+  if (GNUNET_SYSERR ==
+      db_plugin->preflight (db_plugin->cls))
   {
     GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                "Failed to obtain database session!\n");
+                "Failed to obtain database connection!\n");
     global_ret = EXIT_FAILURE;
     GNUNET_SCHEDULER_shutdown ();
     return;
   }
   if (GNUNET_OK !=
       db_plugin->start (db_plugin->cls,
-                        session,
                         "aggregator run transfer"))
   {
     GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
@@ -441,15 +424,12 @@ run_transfers (void *cls)
     return;
   }
   wpd = GNUNET_new (struct WirePrepareData);
-  wpd->session = session;
   qs = db_plugin->wire_prepare_data_get (db_plugin->cls,
-                                         session,
                                          &wire_prepare_cb,
                                          NULL);
   if (GNUNET_DB_STATUS_SUCCESS_ONE_RESULT == qs)
     return;  /* continued via continuation set in #wire_prepare_cb() */
-  db_plugin->rollback (db_plugin->cls,
-                       session);
+  db_plugin->rollback (db_plugin->cls);
   GNUNET_free (wpd);
   wpd = NULL;
   switch (qs)
diff --git a/src/exchange/taler-exchange-wirewatch.c b/src/exchange/taler-exchange-wirewatch.c
index 2993999a8..fb1fde31d 100644
--- a/src/exchange/taler-exchange-wirewatch.c
+++ b/src/exchange/taler-exchange-wirewatch.c
@@ -63,11 +63,6 @@ struct WireAccount
   const struct TALER_EXCHANGEDB_AccountInfo *ai;
 
   /**
-   * Database session we are using for the current transaction.
-   */
-  struct TALER_EXCHANGEDB_Session *session;
-
-  /**
    * Active request for history.
    */
   struct TALER_BANK_CreditHistoryHandle *hh;
@@ -355,8 +350,7 @@ find_transfers (void *cls);
 static void
 handle_soft_error (struct WireAccount *wa)
 {
-  db_plugin->rollback (db_plugin->cls,
-                       wa->session);
+  db_plugin->rollback (db_plugin->cls);
   if (1 < wa->batch_size)
   {
     wa->batch_thresh = wa->batch_size;
@@ -386,7 +380,6 @@ do_commit (struct WireAccount *wa)
   {
     /* shard is complete, mark this as well */
     qs = db_plugin->complete_shard (db_plugin->cls,
-                                    wa->session,
                                     wa->job_name,
                                     wa->shard_start,
                                     wa->shard_end);
@@ -394,8 +387,7 @@ do_commit (struct WireAccount *wa)
     {
     case GNUNET_DB_STATUS_HARD_ERROR:
       GNUNET_break (0);
-      db_plugin->rollback (db_plugin->cls,
-                           wa->session);
+      db_plugin->rollback (db_plugin->cls);
       GNUNET_SCHEDULER_shutdown ();
       return;
     case GNUNET_DB_STATUS_SOFT_ERROR:
@@ -413,8 +405,7 @@ do_commit (struct WireAccount *wa)
       break;
     }
   }
-  qs = db_plugin->commit (db_plugin->cls,
-                          wa->session);
+  qs = db_plugin->commit (db_plugin->cls);
   switch (qs)
   {
   case GNUNET_DB_STATUS_HARD_ERROR:
@@ -432,7 +423,6 @@ do_commit (struct WireAccount *wa)
   }
   /* transaction success, update #last_row_off */
   wa->batch_start = wa->latest_row_off;
-  wa->session = NULL;     /* should not be needed */
   if (wa->batch_size < MAXIMUM_BATCH_SIZE)
   {
     int delta;
@@ -492,7 +482,6 @@ history_cb (void *cls,
             const json_t *json)
 {
   struct WireAccount *wa = cls;
-  struct TALER_EXCHANGEDB_Session *session = wa->session;
   enum GNUNET_DB_QueryStatus qs;
 
   (void) json;
@@ -518,8 +507,7 @@ history_cb (void *cls,
                 "Serial ID %llu not monotonic (got %llu before). Failing!\n",
                 (unsigned long long) serial_id,
                 (unsigned long long) wa->latest_row_off);
-    db_plugin->rollback (db_plugin->cls,
-                         session);
+    db_plugin->rollback (db_plugin->cls);
     GNUNET_SCHEDULER_shutdown ();
     wa->hh = NULL;
     return GNUNET_SYSERR;
@@ -547,7 +535,6 @@ history_cb (void *cls,
      (Note: this may require changing both the
      plugin API as well as modifying how this function is called.) */
   qs = db_plugin->reserves_in_insert (db_plugin->cls,
-                                      session,
                                       &details->reserve_pub,
                                       &details->amount,
                                       details->execution_date,
@@ -558,8 +545,7 @@ history_cb (void *cls,
   {
   case GNUNET_DB_STATUS_HARD_ERROR:
     GNUNET_break (0);
-    db_plugin->rollback (db_plugin->cls,
-                         session);
+    db_plugin->rollback (db_plugin->cls);
     GNUNET_SCHEDULER_shutdown ();
     wa->hh = NULL;
     return GNUNET_SYSERR;
@@ -590,23 +576,22 @@ history_cb (void *cls,
 static void
 find_transfers (void *cls)
 {
-  struct TALER_EXCHANGEDB_Session *session;
   enum GNUNET_DB_QueryStatus qs;
   unsigned int limit;
 
   (void) cls;
   task = NULL;
-  if (NULL == (session = db_plugin->get_session (db_plugin->cls)))
+  if (GNUNET_SYSERR ==
+      db_plugin->preflight (db_plugin->cls))
   {
     GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
-                "Failed to obtain database session!\n");
+                "Failed to obtain database connection!\n");
     global_ret = EXIT_FAILURE;
     GNUNET_SCHEDULER_shutdown ();
     return;
   }
   wa_pos->delay = true;
   wa_pos->current_batch_size = 0; /* reset counter */
-  wa_pos->session = session;
   if (wa_pos->shard_end <= wa_pos->batch_start)
   {
     uint64_t start;
@@ -662,7 +647,6 @@ find_transfers (void *cls)
   }
   if (GNUNET_OK !=
       db_plugin->start_read_committed (db_plugin->cls,
-                                       session,
                                        "wirewatch check for incoming wire transfers"))
   {
     GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
@@ -689,8 +673,7 @@ find_transfers (void *cls)
   {
     GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                 "Failed to start request for account history!\n");
-    db_plugin->rollback (db_plugin->cls,
-                         session);
+    db_plugin->rollback (db_plugin->cls);
     global_ret = EXIT_FAILURE;
     GNUNET_SCHEDULER_shutdown ();
     return;
diff --git a/src/exchange/test_taler_exchange_httpd_restart.sh b/src/exchange/test_taler_exchange_httpd_restart.sh
deleted file mode 100755
index 26a315bf8..000000000
--- a/src/exchange/test_taler_exchange_httpd_restart.sh
+++ /dev/null
@@ -1,107 +0,0 @@
-#!/bin/bash
-#
-# This file is part of TALER
-# Copyright (C) 2020 Taler Systems SA
-#
-#  TALER is free software; you can redistribute it and/or modify it under the
-#  terms of the GNU Affero General Public License as published by the Free Software
-#  Foundation; either version 3, or (at your option) any later version.
-#
-#  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
-#  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
-#  A PARTICULAR PURPOSE.  See the GNU Affero General Public License for more details.
-#
-#  You should have received a copy of the GNU Affero General Public License along with
-#  TALER; see the file COPYING.  If not, If not, see <http://www.gnu.org/licenses/>
-#
-#
-# This script launches an exchange (binding to a UNIX domain socket) and then
-# restarts it in various ways (SIGHUP to re-read configuration, and SIGUSR1 to
-# re-spawn a new binary).  Basically, the goal is to make sure that the HTTP
-# server survives these less common operations.
-#
-#
-set -eu
-
-# Exit, with status code "skip" (no 'real' failure)
-function exit_skip() {
-    echo $1
-    exit 77
-}
-
-# Exit, with error message (hard failure)
-function exit_fail() {
-    echo $1
-    kill `jobs -p` >/dev/null 2>/dev/null || true
-    wait
-    exit 1
-}
-
-echo -n "Testing for curl"
-curl --version >/dev/null </dev/null || exit_skip " MISSING"
-echo " FOUND"
-
-
-# Clear environment from variables that override config.
-unset XDG_DATA_HOME
-unset XDG_CONFIG_HOME
-#
-echo -n "Launching exchange ..."
-PREFIX=
-# Uncomment this line to run with valgrind...
-# PREFIX="valgrind --trace-children=yes --leak-check=yes --track-fds=yes --error-exitcode=1 --log-file=valgrind.%p"
-
-CONFIG=test_taler_exchange_unix.conf
-
-# Setup database
-taler-exchange-dbinit -c $CONFIG &> /dev/null
-# Run Exchange HTTPD (in background)
-$PREFIX taler-exchange-httpd -c $CONFIG 2> test-exchange.log &
-
-# Where should we be bound to?
-UNIXPATH=`taler-config -c $CONFIG -s exchange -f -o UNIXPATH`
-
-# Give HTTP time to start
-
-for n in `seq 1 100`
-do
-    echo -n "."
-    sleep 0.1
-    OK=1
-    curl --unix-socket "${UNIXPATH}" "http://ignored/" >/dev/null 2> /dev/null && break
-    OK=0
-done
-if [ 1 != $OK ]
-then
-    exit_fail "Failed to launch exchange"
-fi
-echo " DONE"
-
-# Finally run test...
-echo -n "Restarting program ..."
-kill -SIGHUP $!
-sleep 1
-curl --unix-socket "${UNIXPATH}" "http://ignored/" >/dev/null 2> /dev/null || exit_fail "SIGHUP killed HTTP service"
-echo " DONE"
-
-echo -n "Waiting for parent to die ..."
-wait $!
-echo " DONE"
-
-echo -n "Testing child still alive ..."
-curl --unix-socket "${UNIXPATH}" "http://ignored/" >/dev/null 2> /dev/null || exit_fail "SIGHUP killed HTTP service"
-echo " DONE"
-
-
-echo -n "Killing grandchild ..."
-CPID=`ps x | grep taler-exchange-httpd | grep -v grep | awk '{print $1}'`
-kill -TERM $CPID
-while true
-do
-    ps x | grep -v grep | grep taler-exchange-httpd > /dev/null || break
-    sleep 0.1
-done
-echo " DONE"
-
-# Return status code from exchange for this script
-exit 0