add taler-merchant-depositcheck to build

2 files changed, 425 insertions, 164 deletions

diff --git a/src/backend/Makefile.am b/src/backend/Makefile.am
index 7978258d..2fe09eec 100644
--- a/src/backend/Makefile.am
+++ b/src/backend/Makefile.am
@@ -16,6 +16,7 @@ EXTRA_DIST = \
   $(pkgcfg_DATA)
 
 bin_PROGRAMS = \
+  taler-merchant-depositcheck \
   taler-merchant-exchange \
   taler-merchant-httpd \
   taler-merchant-webhook \
@@ -226,6 +227,22 @@ taler_merchant_webhook_LDADD = \
 taler_merchant_webhook_CFLAGS = \
   $(AM_CFLAGS)
 
+taler_merchant_depositcheck_SOURCES = \
+  taler-merchant-depositcheck.c
+taler_merchant_depositcheck_LDADD = \
+  $(top_builddir)/src/backenddb/libtalermerchantdb.la \
+  -ltalerexchange \
+  -ltalerjson \
+  -ltalerutil \
+  -ltalerpq \
+  -ljansson \
+  -lgnunetcurl \
+  -lgnunetjson \
+  -lgnunetutil \
+  -lcurl \
+  $(XLIB)
+taler_merchant_depositcheck_CFLAGS = \
+  $(AM_CFLAGS)
 
 taler_merchant_wirewatch_SOURCES = \
   taler-merchant-wirewatch.c
diff --git a/src/backend/taler-merchant-depositcheck.c b/src/backend/taler-merchant-depositcheck.c
index 6982d891..4364c9f5 100644
--- a/src/backend/taler-merchant-depositcheck.c
+++ b/src/backend/taler-merchant-depositcheck.c
@@ -26,37 +26,59 @@
 #include "taler_merchantdb_plugin.h"
 #include <taler/taler_dbevents.h>
 
+/**
+ * How many requests do we make at most in parallel to the same exchange?
+ */
+#define CONCURRENCY_LIMIT 32
+
 
 /**
  * Information we keep per exchange.
  */
-struct ExchangeState
+struct Child
 {
 
   /**
    * Kept in a DLL.
    */
-  struct ExchangeState *next;
+  struct Child *next;
 
   /**
    * Kept in a DLL.
    */
-  struct ExchangeState *prev;
+  struct Child *prev;
+
+  /**
+   * The child process.
+   */
+  struct GNUNET_OS_Process *process;
+
+  /**
+   * Wait handle.
+   */
+  struct GNUNET_ChildWaitHandle *cwh;
 
   /**
    * Which exchange is this state for?
    */
-  const char *base_url;
+  char *base_url;
 
   /**
-   * Key material of the exchange.
+   * Task to restart the child.
    */
-  struct TALER_EXCHANGE_Keys *keys;
+  struct GNUNET_SCHEDULER_Task *rt;
 
   /**
-   * Handle for active /keys request.
+   * When should the child be restarted at the earliest?
    */
-  struct TALER_EXCHANGE_GetKeysHandle *gkh;
+  struct GNUNET_TIME_Absolute next_start;
+
+  /**
+   * Current minimum delay between restarts, grows
+   * exponentially if child exits befor this time.
+   */
+  struct GNUNET_TIME_Relative rd;
+
 };
 
 
@@ -76,9 +98,9 @@ struct ExchangeInteraction
   struct ExchangeInteraction *prev;
 
   /**
-   * Exchange we are interacting with.
+   * Handle for exchange interaction.
    */
-  struct ExchangeState *es;
+  struct TALER_EXCHANGE_DepositGetHandle *dgh;
 
   /**
    * Wire deadline for the deposit.
@@ -115,18 +137,39 @@ struct ExchangeInteraction
    */
   struct TALER_MerchantPrivateKeyP merchant_priv;
 
+  /**
+   * Serial number of the row in the deposits table
+   * that we are processing.
+   */
+  uint64_t deposit_serial;
+
+  /**
+   * The instance the deposit belongs to.
+   */
+  char *instance_id;
+
 };
 
 
 /**
- * Head of list of exchanges we interact with.
+ * Head of list of children we forked.
+ */
+static struct Child *c_head;
+
+/**
+ * Tail of list of children we forked.
+ */
+static struct Child *c_tail;
+
+/**
+ * Key material of the exchange.
  */
-static struct ExchangeState *e_head;
+static struct TALER_EXCHANGE_Keys *keys;
 
 /**
- * Tail of list of exchanges we interact with.
+ * Handle for active /keys request.
  */
-static struct ExchangeState *e_tail;
+static struct TALER_EXCHANGE_GetKeysHandle *gkh;
 
 /**
  * Head of list of active exchange interactions.
@@ -139,6 +182,11 @@ static struct ExchangeInteraction *w_head;
 static struct ExchangeInteraction *w_tail;
 
 /**
+ * Number of active entries in the @e w_head list.
+ */
+static uint64_t w_count;
+
+/**
  * Notification handler from database on new work.
  */
 static struct GNUNET_DB_EventHandler *eh;
@@ -149,6 +197,11 @@ static struct GNUNET_DB_EventHandler *eh;
 static const struct GNUNET_CONFIGURATION_Handle *cfg;
 
 /**
+ * Name of the configuration file we use.
+ */
+static const char *cfg_filename;
+
+/**
  * Our database plugin.
  */
 static struct TALER_MERCHANTDB_Plugin *db_plugin;
@@ -174,6 +227,12 @@ static struct GNUNET_CURL_Context *ctx;
 static struct GNUNET_CURL_RescheduleContext *rc;
 
 /**
+ * Which exchange are we monitoring? NULL if we
+ * are the parent of the workers.
+ */
+static char *exchange_url;
+
+/**
  * Value to return from main(). 0 on success, non-zero on errors.
  */
 static int global_ret;
@@ -192,7 +251,7 @@ static int test_mode;
 static void
 shutdown_task (void *cls)
 {
-  struct ExchangeState *es;
+  struct Child *c;
   struct ExchangeInteraction *w;
 
   (void) cls;
@@ -208,24 +267,70 @@ shutdown_task (void *cls)
     GNUNET_SCHEDULER_cancel (task);
     task = NULL;
   }
+  if (NULL != gkh)
+  {
+    TALER_EXCHANGE_get_keys_cancel (gkh);
+    gkh = NULL;
+  }
   while (NULL != (w = w_head))
   {
     GNUNET_CONTAINER_DLL_remove (w_head,
                                  w_tail,
                                  w);
+    if (NULL != w->dgh)
+    {
+      TALER_EXCHANGE_deposits_get_cancel (w->dgh);
+      w->dgh = NULL;
+    }
+    w_count--;
+    GNUNET_free (w->instance_id);
     GNUNET_free (w);
   }
-  while (NULL != (es = e_head))
+  while (NULL != (c = c_head))
+  {
+    enum GNUNET_OS_ProcessStatusType type;
+    unsigned long code;
+
+    GNUNET_CONTAINER_DLL_remove (c_head,
+                                 c_tail,
+                                 c);
+    if (NULL != c->rt)
+    {
+      GNUNET_SCHEDULER_cancel (c->rt);
+      c->rt = NULL;
+    }
+    if (NULL != c->cwh)
+    {
+      GNUNET_wait_child_cancel (c->cwh);
+      c->cwh = NULL;
+    }
+    if (NULL != c->process)
+    {
+      GNUNET_break (0 ==
+                    GNUNET_OS_process_kill (c->process,
+                                            SIGTERM));
+      GNUNET_break (GNUNET_OK ==
+                    GNUNET_OS_process_wait_status (c->process,
+                                                   &type,
+                                                   &code));
+      if ( (GNUNET_OS_PROCESS_EXITED != type) ||
+           (0 != code) )
+        GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                    "Process for exchange %s had trouble (%d/%d)\n",
+                    c->base_url,
+                    (int) type,
+                    (int) code);
+      GNUNET_OS_process_destroy (c->process);
+    }
+    GNUNET_free (c->base_url);
+    GNUNET_free (c);
+  }
+  if (NULL != db_plugin)
   {
-    GNUNET_CONTAINER_DLL_remove (e_head,
-                                 e_tail,
-                                 es);
-    GNUNET_free (es->base_url);
-    GNUNET_free (es);
+    db_plugin->rollback (db_plugin->cls); /* just in case */
+    TALER_MERCHANTDB_plugin_unload (db_plugin);
+    db_plugin = NULL;
   }
-  db_plugin->rollback (db_plugin->cls); /* just in case */
-  TALER_MERCHANTDB_plugin_unload (db_plugin);
-  db_plugin = NULL;
   cfg = NULL;
   if (NULL != ctx)
   {
@@ -253,22 +358,21 @@ select_work (void *cls);
  * Make sure to run the select_work() task at
  * the @a next_deadline.
  *
- * @param next_deadline deadline when work becomes ready
+ * @param deadline time when work becomes ready
  */
 static void
-run_at (struct GNUNET_TIME_Absolute next_deadline)
+run_at (struct GNUNET_TIME_Absolute deadline)
 {
   if (GNUNET_TIME_absolute_cmp (deadline,
-                                <,
+                                >,
                                 next_deadline))
-  {
-    if (NULL != task)
-      GNUNET_SCHEDULER_cancel (task);
-    next_deadline = deadline;
-    task = GNUNET_SCHEDULER_add_at (deadline,
-                                    &select_work,
-                                    NULL);
-  }
+    return;
+  if (NULL != task)
+    GNUNET_SCHEDULER_cancel (task);
+  next_deadline = deadline;
+  task = GNUNET_SCHEDULER_add_at (deadline,
+                                  &select_work,
+                                  NULL);
 }
 
 
@@ -282,7 +386,7 @@ static void
 deposit_get_cb (void *cls,
                 const struct TALER_EXCHANGE_GetDepositResponse *dr)
 {
-  struct ExchangeState *es = cls;
+  struct ExchangeInteraction *w = cls;
 
   switch (dr->hr.http_status)
   {
@@ -293,10 +397,12 @@ deposit_get_cb (void *cls,
       GNUNET_log (GNUNET_ERROR_TYPE_INFO,
                   "Exchange returned wire transfer over %s for deposited coin %s\n",
                   TALER_amount2s (&dr->details.ok.coin_contribution),
-                  TALER_B2S (&tq->coin_pub));
-      qs = TMH_db->insert_deposit_to_transfer (TMH_db->cls,
-                                               tq->deposit_serial,
-                                               &dr->details.ok);
+                  TALER_B2S (&w->coin_pub));
+      // FIXME: this must filter this particular entry from the
+      // select below for good!
+      qs = db_plugin->insert_deposit_to_transfer (db_plugin->cls,
+                                                  w->deposit_serial,
+                                                  &dr->details.ok);
       if (qs < 0)
       {
         GNUNET_break (0);
@@ -316,13 +422,16 @@ deposit_get_cb (void *cls,
                   "Exchange returned KYC requirement (%d/%d) for deposited coin %s\n",
                   dr->details.accepted.kyc_ok,
                   dr->details.accepted.aml_decision,
-                  TALER_B2S (&tq->coin_pub));
+                  TALER_B2S (&w->coin_pub));
       now = GNUNET_TIME_timestamp_get ();
-      qs = TMH_db->account_kyc_set_status (
-        TMH_db->cls,
-        gorc->hc->instance->settings.id,
-        &tq->h_wire,
-        tq->exchange_url,
+      // FIXME: this must filter this particular entry from the
+      // select below, at least until the KYC/AML request is
+      // satisfied; how will we learn that?
+      qs = db_plugin->account_kyc_set_status (
+        db_plugin->cls,
+        w->instance_id,
+        &w->h_wire,
+        exchange_url,
         dr->details.accepted.requirement_row,
         NULL,
         NULL,
@@ -340,8 +449,9 @@ deposit_get_cb (void *cls,
   default:
     {
       GNUNET_log (GNUNET_ERROR_TYPE_INFO,
-                  "Exchange returned tracking failure for deposited coin %s\n",
-                  TALER_B2S (&tq->coin_pub));
+                  "Exchange %s returned tracking failure for deposited coin %s\n",
+                  exchange_url,
+                  TALER_B2S (&w->coin_pub));
       /* FIXME: how to handle? */
       return;
     }
@@ -350,107 +460,26 @@ deposit_get_cb (void *cls,
   GNUNET_CONTAINER_DLL_remove (w_head,
                                w_tail,
                                w);
+  w_count--;
   GNUNET_free (w);
-  // FIXME: not the best condition to go for more work,
-  // one down exchange would halt us entirely!
-  if (NULL == w_head)
+  if ( (w_count < CONCURRENCY_LIMIT / 2) ||
+       (0 == w_count) )
     task = GNUNET_SCHEDULER_add_now (&select_work,
                                      NULL);
 }
 
 
 /**
- * Initiate request with the exchange about deposits.
- *
- * @param[in,out] exchange interaction handle
- */
-static void
-inquire_at_exchange (struct ExchangeInteraction *w)
-{
-  struct ExchangeState *es = w->es;
-
-  GNUNET_assert (NULL == w->dgh);
-  w->dgh = TALER_EXCHANGE_deposits_get (
-    ctx,
-    es->exchange_url,
-    es->keys,
-    &w->merchant_priv,
-    &w->h_wire,
-    &w->h_contract_terms,
-    &w->coin_pub,
-    GNUNET_TIME_UNIT_ZERO,
-    &deposit_get_cb,
-    w);
-}
-
-
-/**
- * Function called with information about who is auditing
- * a particular exchange and what keys the exchange is using.
- * The ownership over the @a keys object is passed to
- * the callee, thus it is given explicitly and not
- * (only) via @a kr.
- *
- * @param cls closure
- * @param kr response from /keys
- * @param[in] keys keys object passed to callback with
- *  reference counter of 1. Must be freed by callee
- *  using #TALER_EXCHANGE_keys_decref(). NULL on failure.
- */
-static void
-keys_cb (
-  void *cls,
-  const struct TALER_EXCHANGE_KeysResponse *kr,
-  struct TALER_EXCHANGE_Keys *keys)
-{
-  struct ExchangeState *es = cls;
-
-  es->gkh = NULL;
-  if (NULL == keys)
-    return;
-  if (NULL != es->keys)
-    TALER_EXCHANGE_keys_decref (keys);
-  es->keys = TALER_EXCHANGE_keys_incref (keys);
-  /* Trigger all deposits blocked on fetching /keys */
-  for (struct ExchangeInteraction *w = w_head;
-       NULL != w;
-       w = w->next)
-  {
-    if (w->es != es)
-      continue;
-    if (NULL != w->dgh)
-      continue;
-    inquire_at_exchange (w);
-  }
-}
-
-
-/**
- * Download /keys from an exchange.
- *
- * @param[in,out] es exchange state
- */
-static void
-fetch_keys (struct ExchangeState *es)
-{
-  GNUNET_assert (NULL == es->gkh);
-  es->gkh = TALER_EXCHANGE_get_keys (ctx,
-                                     es->base_url,
-                                     es->keys,
-                                     &keys_cb,
-                                     es);
-}
-
-
-/**
  * Typically called by `select_work`.
  *
  * @param cls NULL
  * @param deposit_serial identifies the deposit operation
- * @param exchange_url URL of the exchange that issued @a coin_pub
- * @param amount_with_fee amount the exchange will deposit for this coin
- * @param deposit_fee fee the exchange will charge for this coin
- * @param h_wire hash of the merchant's wire account into which the deposit was made
+ * @param wire_deadline when is the wire due
+ * @param h_contract_terms hash of the contract terms
+ * @param merchant_priv private key of the merchant
+ * @param instance_id row ID of the instance
+ * @param h_wire hash of the merchant's wire account into  * @param amount_with_fee amount the exchange will deposit for this coin
+ * @param deposit_fee fee the exchange will charge for this coin which the deposit was made
  * @param coin_pub public key of the deposited coin
  */
 static void
@@ -458,16 +487,15 @@ pending_deposits_cb (
   void *cls,
   uint64_t deposit_serial,
   struct GNUNET_TIME_Absolute wire_deadline, /* missing in DB! Funky migration needed! */
-  const char *exchange_url,
   const struct TALER_PrivateContractHashP *h_contract_terms,
   const struct TALER_MerchantPrivateKeyP *merchant_priv,
+  const char *instance_id,
   const struct TALER_MerchantWireHashP *h_wire,
   const struct TALER_Amount *amount_with_fee,
   const struct TALER_Amount *deposit_fee,
   const struct TALER_CoinSpendPublicKeyP *coin_pub)
 {
   struct ExchangeInteraction *w = GNUNET_new (struct ExchangeInteraction);
-  struct ExchangeState *es = NULL;
 
   (void) cls;
   if (GNUNET_TIME_absolute_is_future (wire_deadline))
@@ -475,6 +503,7 @@ pending_deposits_cb (
     run_at (wire_deadline);
     return;
   }
+  w->deposit_serial = deposit_serial;
   w->wire_deadline = wire_deadline;
   w->h_contract_terms = *h_contract_terms;
   w->merchant_priv = *merchant_priv;
@@ -482,29 +511,30 @@ pending_deposits_cb (
   w->amount_with_fee = *amount_with_fee;
   w->deposit_fee = *deposit_fee;
   w->coin_pub = *coin_pub;
+  w->instance_id = GNUNET_strdup (instance_id);
   GNUNET_CONTAINER_DLL_insert (w_head,
                                w_tail,
                                w);
-  for (es = e_head; NULL != es; es = es->next)
-    if (0 == strcmp (exchange_url,
-                     es->base_url))
-      break;
-  if (NULL == es)
+  w_count++;
+  GNUNET_assert (NULL != keys);
+  if (GNUNET_TIME_absolute_is_past (keys->key_data_expiration.abs_time))
   {
-    es = GNUNET_new (struct ExchangeState);
-    es->base_url = GNUNET_strdup (exchange_url);
-    GNUNET_CONTAINER_DLL_insert (e_head,
-                                 e_tail,
-                                 es);
-  }
-  w->es = es;
-  if ( (NULL == es->keys) ||
-       (GNUNET_TIME_absolute_is_past (es->keys->key_data_expiration)) )
-  {
-    fetch_keys (es);
+    /* Parent should re-start us, then we will re-fetch /keys */
+    GNUNET_SCHEDULER_shutdown ();
     return;
   }
-  inquire_at_exchange (w);
+  GNUNET_assert (NULL == w->dgh);
+  w->dgh = TALER_EXCHANGE_deposits_get (
+    ctx,
+    exchange_url,
+    keys,
+    &w->merchant_priv,
+    &w->h_wire,
+    &w->h_contract_terms,
+    &w->coin_pub,
+    GNUNET_TIME_UNIT_ZERO,
+    &deposit_get_cb,
+    w);
 }
 
 
@@ -529,6 +559,8 @@ db_notify (void *cls,
     GNUNET_break (0);
     return;
   }
+  if (0 != w_count)
+    return; /* already at work! */
   memcpy (&nbo_deadline,
           extra,
           extra_size);
@@ -541,18 +573,35 @@ static void
 select_work (void *cls)
 {
   bool retry = false;
+  uint32_t limit = CONCURRENCY_LIMIT - w_count;
 
   (void) cls;
   task = NULL;
+  GNUNET_assert (NULL != keys);
+  if (GNUNET_TIME_absolute_is_past (keys->key_data_expiration.abs_time))
+  {
+    /* Parent should re-start us, then we will re-fetch /keys */
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
   while (1)
   {
-    struct GNUNET_TIME_Absolute now;
     enum GNUNET_DB_QueryStatus qs;
 
-    now = GNUNET_TIME_absolute_get ();
     db_plugin->preflight (db_plugin->cls);
+    // NOTE:
+    // SQL must filter all deposits for accounts
+    // that are already KYC/AML-blocked!
+    // (FIXME: How do we then learn about KYC unblocking?)
+    // Usually, select up to limit
+    // deposits with wire deadlines < now,
+    // or *1* deposit with smallest wire deadline if
+    // retry is 'true'.
+    if (retry)
+      limit = 1;
     qs = db_plugin->lookup_pending_deposits (db_plugin->cls,
-                                             now,
+                                             exchange_url,
+                                             limit,
                                              retry,
                                              &pending_deposits_cb,
                                              NULL);
@@ -582,6 +631,178 @@ select_work (void *cls)
 
 
 /**
+ * Function called with information about who is auditing
+ * a particular exchange and what keys the exchange is using.
+ * The ownership over the @a keys object is passed to
+ * the callee, thus it is given explicitly and not
+ * (only) via @a kr.
+ *
+ * @param cls closure, NULL
+ * @param kr response from /keys
+ * @param[in] keys keys object passed to callback with
+ *  reference counter of 1. Must be freed by callee
+ *  using #TALER_EXCHANGE_keys_decref(). NULL on failure.
+ */
+static void
+keys_cb (
+  void *cls,
+  const struct TALER_EXCHANGE_KeysResponse *kr,
+  struct TALER_EXCHANGE_Keys *keys)
+{
+  gkh = NULL;
+  if (NULL == keys)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                "Failed to download %skeys\n",
+                exchange_url);
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
+  keys = TALER_EXCHANGE_keys_incref (keys);
+  GNUNET_assert (NULL == task);
+  task = GNUNET_SCHEDULER_add_now (&select_work,
+                                   NULL);
+}
+
+
+/**
+ * Start a copy of this process with the exchange URL
+ * set to the given @a base_url
+ *
+ * @param base_url base URL to run with
+ */
+static struct GNUNET_OS_Process *
+start_worker (const char *base_url)
+{
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+              "Launching worker for exchange `%s'\n",
+              base_url);
+  return GNUNET_OS_start_process (GNUNET_OS_INHERIT_STD_ALL,
+                                  NULL,
+                                  NULL,
+                                  NULL,
+                                  "taler-merchant-depositcheck",
+                                  "-c", cfg_filename,
+                                  "-e", base_url,
+                                  NULL);
+}
+
+
+/**
+ * Restart worker process for the given child.
+ *
+ * @param cls a `struct Child *` that needs a worker.
+ */
+static void
+restart_child (void *cls);
+
+
+/**
+ * Function called upon death or completion of a child process.
+ *
+ * @param cls a `struct Child *`
+ * @param type type of the process
+ * @param exit_code status code of the process
+ */
+static void
+child_done_cb (void *cls,
+               enum GNUNET_OS_ProcessStatusType type,
+               long unsigned int exit_code)
+{
+  struct Child *c = cls;
+
+  c->cwh = NULL;
+  if ( (GNUNET_OS_PROCESS_EXITED != type) ||
+       (0 != exit_code) )
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                "Process for exchange %s had trouble (%d/%d)\n",
+                c->base_url,
+                (int) type,
+                (int) exit_code);
+    GNUNET_SCHEDULER_shutdown ();
+    global_ret = 1;
+    return;
+  }
+  GNUNET_OS_process_destroy (c->process);
+  if (GNUNET_TIME_absolute_is_future (c->next_start))
+    c->rd = GNUNET_TIME_STD_BACKOFF (c->rd);
+  else
+    c->rd = GNUNET_TIME_UNIT_SECONDS;
+  c->rt = GNUNET_SCHEDULER_add_at (c->next_start,
+                                   &restart_child,
+                                   c);
+}
+
+
+static void
+restart_child (void *cls)
+{
+  struct Child *c = cls;
+
+  c->rt = NULL;
+  c->next_start = GNUNET_TIME_relative_to_absolute (c->rd);
+  c->process = start_worker (c->base_url);
+  if (NULL == c->process)
+  {
+    GNUNET_log_strerror (GNUNET_ERROR_TYPE_ERROR,
+                         "exec");
+    global_ret = 1;
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
+  c->cwh = GNUNET_wait_child (c->process,
+                              &child_done_cb,
+                              c);
+}
+
+
+/**
+ * Function to iterate over section.
+ *
+ * @param cls closure
+ * @param section name of the section
+ */
+static void
+cfg_iter_cb (void *cls,
+             const char *section)
+{
+  char *base_url;
+  struct Child *c;
+
+  if (0 !=
+      strncasecmp (section,
+                   "merchant-exchange-",
+                   strlen ("merchant-exchange-")))
+    return;
+  if (GNUNET_YES ==
+      GNUNET_CONFIGURATION_get_value_yesno (cfg,
+                                            section,
+                                            "DISABLED"))
+    return;
+  if (GNUNET_OK !=
+      GNUNET_CONFIGURATION_get_value_string (cfg,
+                                             section,
+                                             "EXCHANGE_BASE_URL",
+                                             &base_url))
+  {
+    GNUNET_log_config_missing (GNUNET_ERROR_TYPE_WARNING,
+                               section,
+                               "EXCHANGE_BASE_URL");
+    return;
+  }
+  c = GNUNET_new (struct Child);
+  c->rd = GNUNET_TIME_UNIT_SECONDS;
+  c->base_url = base_url;
+  GNUNET_CONTAINER_DLL_insert (c_head,
+                               c_tail,
+                               c);
+  c->rt = GNUNET_SCHEDULER_add_now (&restart_child,
+                                    c);
+}
+
+
+/**
  * First task.
  *
  * @param cls closure, NULL
@@ -596,11 +817,25 @@ run (void *cls,
      const struct GNUNET_CONFIGURATION_Handle *c)
 {
   (void) args;
-  (void) cfgfile;
 
   cfg = c;
+  cfg_filename = cfgfile;
   GNUNET_SCHEDULER_add_shutdown (&shutdown_task,
                                  NULL);
+  if (NULL == exchange_url)
+  {
+    GNUNET_CONFIGURATION_iterate_sections (c,
+                                           &cfg_iter_cb,
+                                           NULL);
+    if (NULL == c_head)
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
+                  "No exchanges found in configuration\n");
+      return;
+    }
+    return;
+  }
+
   ctx = GNUNET_CURL_init (&GNUNET_CURL_gnunet_scheduler_reschedule,
                           &rc);
   rc = GNUNET_CURL_gnunet_rc_create (ctx);
@@ -616,6 +851,7 @@ run (void *cls,
     GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                 "Failed to initialize DB subsystem\n");
     GNUNET_SCHEDULER_shutdown ();
+    global_ret = 1;
     return;
   }
   if (GNUNET_OK !=
@@ -624,6 +860,7 @@ run (void *cls,
     GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
                 "Failed to connect to database\n");
     GNUNET_SCHEDULER_shutdown ();
+    global_ret = 1;
     return;
   }
   {
@@ -638,9 +875,11 @@ run (void *cls,
                                   &db_notify,
                                   NULL);
   }
-  GNUNET_assert (NULL == task);
-  task = GNUNET_SCHEDULER_add_now (&select_work,
-                                   NULL);
+  gkh = TALER_EXCHANGE_get_keys (ctx,
+                                 exchange_url,
+                                 NULL,
+                                 &keys_cb,
+                                 NULL);
 }
 
 
@@ -656,6 +895,11 @@ main (int argc,
       char *const *argv)
 {
   struct GNUNET_GETOPT_CommandLineOption options[] = {
+    GNUNET_GETOPT_option_string ('e',
+                                 "exchange",
+                                 "BASE_URL",
+                                 "limit us to checking deposits of this exchange",
+                                 &exchange_url),
     GNUNET_GETOPT_option_flag ('t',
                                "test",
                                "run in test mode and exit when idle",