exchange

Base system with REST service to issue digital coins, run by the payment service provider
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commit.c (2920B)

      1 /*
      2    This file is part of TALER
      3    Copyright (C) 2022 Taler Systems SA
      4 
      5    TALER is free software; you can redistribute it and/or modify it under the
      6    terms of the GNU General Public License as published by the Free Software
      7    Foundation; either version 3, or (at your option) any later version.
      8 
      9    TALER is distributed in the hope that it will be useful, but WITHOUT ANY
     10    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
     11    A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
     12 
     13    You should have received a copy of the GNU General Public License along with
     14    TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
     15  */
     16 /**
     17  * @file exchangedb/commit.c
     18  * @brief Implementation of the commit function for Postgres
     19  * @author Christian Grothoff
     20  */
     21 #include "taler/taler_pq_lib.h"
     22 #include "exchange-database/commit.h"
     23 #include "helper.h"
     24 
     25 
     26 /**
     27  * Commit the current transaction of a database connection.
     28  *
     29  * @param pg the database context
     30  * @return final transaction status
     31  */
     32 enum GNUNET_DB_QueryStatus
     33 TALER_EXCHANGEDB_commit (struct TALER_EXCHANGEDB_PostgresContext *pg)
     34 {
     35   struct GNUNET_PQ_QueryParam params[] = {
     36     GNUNET_PQ_query_param_end
     37   };
     38   enum GNUNET_DB_QueryStatus qs;
     39 
     40   GNUNET_break (NULL != pg->transaction_name);
     41   GNUNET_log (GNUNET_ERROR_TYPE_INFO,
     42               "Committing transaction `%s'\n",
     43               pg->transaction_name);
     44   PREPARE (pg,
     45            "commit",
     46            "COMMIT");
     47   {
     48     PGresult *result;
     49 
     50     result = GNUNET_PQ_exec_prepared (pg->conn,
     51                                       "commit",
     52                                       params);
     53     qs = GNUNET_PQ_eval_result (pg->conn,
     54                                 "commit",
     55                                 result);
     56     if ( (0 <= qs) &&
     57          (NULL != result) &&
     58          (0 == strcmp ("ROLLBACK",
     59                        PQcmdStatus (result))) )
     60     {
     61       /* PostgreSQL accepts COMMIT on a transaction it has already aborted:
     62          it silently rolls back and answers PGRES_COMMAND_OK with the command
     63          tag ROLLBACK.  That is indistinguishable from a successful commit to
     64          GNUNET_PQ_eval_result(), so every caller would take the success path
     65          for a transaction whose writes are gone.  Report it as a soft error:
     66          the transaction is almost always aborted by a serialization failure
     67          (we run SERIALIZABLE), so retrying is the right answer, and callers
     68          with a retry loop will give up and fail visibly after
     69          MAX_RETRIES. */
     70       GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
     71                   "Transaction `%s' was rolled back by the database instead of committed; a previous statement must have failed without being handled\n",
     72                   pg->transaction_name);
     73       qs = GNUNET_DB_STATUS_SOFT_ERROR;
     74     }
     75     PQclear (result);
     76   }
     77   pg->transaction_name = NULL;
     78   return qs;
     79 }