exchange

commit 0b6b2f3a05fb8fc77182748ed2693ae9fe50070c
parent 33679d241f5f0d25af328a28d6796a41d6c35e4e
Author: Christian Grothoff <christian@grothoff.org>
Date:   Fri,  9 Oct 2026 22:11:30 +0200

flush coin-history cache between transactions to avoid looking at a stale one

Diffstat:
M
src/auditor/taler-helper-auditor-coins.c
 | 
44
++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 44 insertions(+), 0 deletions(-)
diff --git a/src/auditor/taler-helper-auditor-coins.c b/src/auditor/taler-helper-auditor-coins.c
@@ -169,6 +169,18 @@ struct CoinHistory
 static struct CoinHistory coin_histories[MAX_COIN_HISTORIES];
 
 /**
+ * Indices of the entries of #coin_histories that are in use.  Used to
+ * flush the cache at the end of a pass without touching the entire
+ * (huge) #coin_histories array.
+ */
+static unsigned int *used_histories;
+
+/**
+ * Length of the #used_histories array.
+ */
+static unsigned int num_used_histories;
+
+/**
  * Should we run checks that only work for exchange-internal audits?
  */
 static int internal_checks;
@@ -213,12 +225,43 @@ cache_history (const struct TALER_CoinSpendPublicKeyP *coin_pub,
 
   if (NULL != coin_histories[i].tl)
     TALER_EXCHANGEDB_free_coin_transaction_list (coin_histories[i].tl);
+  else
+    GNUNET_array_append (used_histories,
+                         num_used_histories,
+                         i);
   coin_histories[i].coin_pub = *coin_pub;
   coin_histories[i].tl = tl;
 }
 
 
 /**
+ * Drop all cached coin histories.
+ *
+ * Must be called at the end of each pass: within a pass the history we
+ * fetched is complete (we read it from a consistent snapshot), but the
+ * exchange keeps adding transactions to coins we already saw.  Keeping
+ * the entry across passes would make us skip the over-spending check
+ * for every coin the process has already looked at.
+ */
+static void
+flush_coin_histories (void)
+{
+  for (unsigned int j = 0; j < num_used_histories; j++)
+  {
+    struct CoinHistory *ch = &coin_histories[used_histories[j]];
+
+    TALER_EXCHANGEDB_free_coin_transaction_list (ch->tl);
+    memset (ch,
+            0,
+            sizeof (*ch));
+  }
+  GNUNET_array_grow (used_histories,
+                     num_used_histories,
+                     0);
+}
+
+
+/**
  * Obtain a coin's history from our in-memory cache.
  *
  * @param coin_pub public key of the coin to cache
@@ -2979,6 +3022,7 @@ analyze_coins (void *cls)
                 coins_purse_refunds_serial_id));
   qs = GNUNET_DB_STATUS_SUCCESS_ONE_RESULT;
 cleanup:
+  flush_coin_histories ();
   GNUNET_CONTAINER_multihashmap_iterate (cc.denom_summaries,
                                          &cleanup_denomination,
                                          &cc);