-add skeleton logic for purse expiration

src/exchange/.gitignore

@@ -10,3 +10,4 @@ test_taler_exchange_httpd_home/.config/taler/account-1.json
 taler-exchange-closer
 taler-exchange-transfer
 taler-exchange-router
+taler-exchange-expire

src/exchange/Makefile.am

@@ -19,6 +19,7 @@ pkgcfg_DATA = \
 bin_PROGRAMS = \
   taler-exchange-aggregator \
   taler-exchange-closer \
+  taler-exchange-expire \
   taler-exchange-httpd \
   taler-exchange-router \
   taler-exchange-transfer \
@@ -51,6 +52,19 @@ taler_exchange_closer_LDADD = \
   -lgnunetutil \
   $(XLIB)
 
+taler_exchange_expire_SOURCES = \
+  taler-exchange-expire.c
+taler_exchange_expire_LDADD = \
+  $(LIBGCRYPT_LIBS) \
+  $(top_builddir)/src/json/libtalerjson.la \
+  $(top_builddir)/src/util/libtalerutil.la \
+  $(top_builddir)/src/bank-lib/libtalerbank.la \
+  $(top_builddir)/src/exchangedb/libtalerexchangedb.la \
+  -ljansson \
+  -lgnunetcurl \
+  -lgnunetutil \
+  $(XLIB)
+
 taler_exchange_router_SOURCES = \
   taler-exchange-router.c
 taler_exchange_router_LDADD = \

src/exchange/exchange.conf

@@ -47,8 +47,15 @@ BASE_URL = http://localhost:8081/
 # How long should the aggregator sleep if it has nothing to do?
 AGGREGATOR_IDLE_SLEEP_INTERVAL = 60 s
 
+# FIXME: document!
 ROUTER_IDLE_SLEEP_INTERVAL = 60 s
 
+# How big is an individual shard to be processed
+# by taler-exchange-expire (in time).  It may take
+# this much time for an expired purse to be really
+# cleaned up and the coins refunded.
+EXPIRE_SHARD_SIZE = 5 m
+
 # How long should the transfer tool
 # sleep if it has nothing to do?
 TRANSFER_IDLE_SLEEP_INTERVAL = 60 s

src/exchange/taler-exchange-expire.c

@@ -0,0 +1,479 @@
+/*
+  This file is part of TALER
+  Copyright (C) 2022 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-expire.c
+ * @brief Process that cleans up expired purses
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include <gnunet/gnunet_util_lib.h>
+#include <jansson.h>
+#include <pthread.h>
+#include "taler_exchangedb_lib.h"
+#include "taler_exchangedb_plugin.h"
+#include "taler_json_lib.h"
+#include "taler_bank_service.h"
+
+
+/**
+ * Work shard we are processing.
+ */
+struct Shard
+{
+
+  /**
+   * When did we start processing the shard?
+   */
+  struct GNUNET_TIME_Timestamp start_time;
+
+  /**
+   * Starting row of the shard.
+   */
+  struct GNUNET_TIME_Absolute shard_start;
+
+  /**
+   * Inclusive end row of the shard.
+   */
+  struct GNUNET_TIME_Absolute shard_end;
+
+  /**
+   * Number of starting points found in the shard.
+   */
+  uint64_t work_counter;
+
+};
+
+
+/**
+ * The exchange's configuration.
+ */
+static const struct GNUNET_CONFIGURATION_Handle *cfg;
+
+/**
+ * Our database plugin.
+ */
+static struct TALER_EXCHANGEDB_Plugin *db_plugin;
+
+/**
+ * Next task to run, if any.
+ */
+static struct GNUNET_SCHEDULER_Task *task;
+
+/**
+ * How long should we sleep when idle before trying to find more work?
+ */
+static struct GNUNET_TIME_Relative expire_idle_sleep_interval;
+
+/**
+ * How big are the shards we are processing? Is an inclusive offset, so every
+ * shard ranges from [X,X+shard_size) exclusive.  So a shard covers
+ * shard_size slots.
+ */
+static struct GNUNET_TIME_Relative shard_size;
+
+/**
+ * Value to return from main(). 0 on success, non-zero on errors.
+ */
+static int global_ret;
+
+/**
+ * #GNUNET_YES if we are in test mode and should exit when idle.
+ */
+static int test_mode;
+
+
+/**
+ * Select a shard to work on.
+ *
+ * @param cls NULL
+ */
+static void
+run_shard (void *cls);
+
+
+/**
+ * We're being aborted with CTRL-C (or SIGTERM). Shut down.
+ *
+ * @param cls closure
+ */
+static void
+shutdown_task (void *cls)
+{
+  (void) cls;
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+              "Running shutdown\n");
+  if (NULL != task)
+  {
+    GNUNET_SCHEDULER_cancel (task);
+    task = NULL;
+  }
+  TALER_EXCHANGEDB_plugin_unload (db_plugin);
+  db_plugin = NULL;
+  cfg = NULL;
+}
+
+
+/**
+ * Parse the configuration for expire.
+ *
+ * @return #GNUNET_OK on success
+ */
+static enum GNUNET_GenericReturnValue
+parse_expire_config (void)
+{
+  if (GNUNET_OK !=
+      GNUNET_CONFIGURATION_get_value_time (cfg,
+                                           "exchange",
+                                           "EXPIRE_IDLE_SLEEP_INTERVAL",
+                                           &expire_idle_sleep_interval))
+  {
+    GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
+                               "exchange",
+                               "EXPIRE_IDLE_SLEEP_INTERVAL");
+    return GNUNET_SYSERR;
+  }
+  if (NULL ==
+      (db_plugin = TALER_EXCHANGEDB_plugin_load (cfg)))
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "Failed to initialize DB subsystem\n");
+    return GNUNET_SYSERR;
+  }
+  return GNUNET_OK;
+}
+
+
+/**
+ * Perform a database commit. If it fails, print a warning.
+ *
+ * @return status of commit
+ */
+static enum GNUNET_DB_QueryStatus
+commit_or_warn (void)
+{
+  enum GNUNET_DB_QueryStatus qs;
+
+  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)
+              ? GNUNET_ERROR_TYPE_INFO
+              : GNUNET_ERROR_TYPE_ERROR,
+              "Failed to commit database transaction!\n");
+  return qs;
+}
+
+
+/**
+ * Release lock on shard @a s in the database.
+ * On error, terminates this process.
+ *
+ * @param[in] s shard to free (and memory to release)
+ */
+static void
+release_shard (struct Shard *s)
+{
+  enum GNUNET_DB_QueryStatus qs;
+
+  qs = db_plugin->complete_shard (
+    db_plugin->cls,
+    "expire",
+    s->shard_start.abs_value_us,
+    s->shard_end.abs_value_us);
+  GNUNET_free (s);
+  switch (qs)
+  {
+  case GNUNET_DB_STATUS_HARD_ERROR:
+  case GNUNET_DB_STATUS_SOFT_ERROR:
+    GNUNET_break (GNUNET_DB_STATUS_SOFT_ERROR != qs);
+    GNUNET_break (0);
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
+    /* Strange, but let's just continue */
+    break;
+  case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
+    GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+                "Purse expiration shard completed with %llu purses\n",
+                (unsigned long long) s->work_counter);
+    /* normal case */
+    break;
+  }
+}
+
+
+/**
+ * Release lock on shard @a s in the database due to an abort of the
+ * operation.  On error, terminates this process.
+ *
+ * @param[in] s shard to free (and memory to release)
+ */
+static void
+abort_shard (struct Shard *s)
+{
+  enum GNUNET_DB_QueryStatus qs;
+
+  qs = db_plugin->abort_shard (db_plugin->cls,
+                               "expire",
+                               s->shard_start.abs_value_us,
+                               s->shard_end.abs_value_us);
+  if (0 >= qs)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "Failed to abort shard (%d)!\n",
+                qs);
+    global_ret = EXIT_FAILURE;
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
+}
+
+
+/**
+ * Main function that processes the work in one shard.
+ *
+ * @param[in] cls a `struct Shard` to process
+ */
+static void
+run_expire (void *cls)
+{
+  struct Shard *s = cls;
+  enum GNUNET_DB_QueryStatus qs;
+
+  task = NULL;
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+              "Checking for expired purses\n");
+  if (GNUNET_SYSERR ==
+      db_plugin->preflight (db_plugin->cls))
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "Failed to obtain database connection!\n");
+    global_ret = EXIT_FAILURE;
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
+  if (db_plugin->start (db_plugin->cls,
+                        "expire-purse"))
+  {
+    global_ret = EXIT_FAILURE;
+    db_plugin->rollback (db_plugin->cls);
+    abort_shard (s);
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
+  qs = db_plugin->expire_purse (db_plugin->cls,
+                                s->shard_start,
+                                s->shard_end);
+  switch (qs)
+  {
+  case GNUNET_DB_STATUS_HARD_ERROR:
+    GNUNET_break (0);
+    global_ret = EXIT_FAILURE;
+    db_plugin->rollback (db_plugin->cls);
+    abort_shard (s);
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  case GNUNET_DB_STATUS_SOFT_ERROR:
+    db_plugin->rollback (db_plugin->cls);
+    abort_shard (s);
+    task = GNUNET_SCHEDULER_add_now (&run_shard,
+                                     NULL);
+    return;
+  case GNUNET_DB_STATUS_SUCCESS_NO_RESULTS:
+    if (0 > commit_or_warn ())
+    {
+      db_plugin->rollback (db_plugin->cls);
+      abort_shard (s);
+    }
+    else
+    {
+      release_shard (s);
+    }
+    task = GNUNET_SCHEDULER_add_now (&run_shard,
+                                     NULL);
+    return;
+  case GNUNET_DB_STATUS_SUCCESS_ONE_RESULT:
+    /* commit, and go again immediately */
+    s->work_counter++;
+    (void) commit_or_warn ();
+    task = GNUNET_SCHEDULER_add_now (&run_expire,
+                                     s);
+  }
+}
+
+
+/**
+ * Select a shard to work on.
+ *
+ * @param cls NULL
+ */
+static void
+run_shard (void *cls)
+{
+  struct Shard *s;
+  enum GNUNET_DB_QueryStatus qs;
+
+  (void) cls;
+  task = NULL;
+  if (GNUNET_SYSERR ==
+      db_plugin->preflight (db_plugin->cls))
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "Failed to obtain database connection!\n");
+    global_ret = EXIT_FAILURE;
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
+  s = GNUNET_new (struct Shard);
+  s->start_time = GNUNET_TIME_timestamp_get ();
+  qs = db_plugin->begin_shard (db_plugin->cls,
+                               "expire",
+                               shard_size,
+                               shard_size.rel_value_us,
+                               &s->shard_start.abs_value_us,
+                               &s->shard_end.abs_value_us);
+  if (0 >= qs)
+  {
+    if (GNUNET_DB_STATUS_SOFT_ERROR == qs)
+    {
+      static struct GNUNET_TIME_Relative delay;
+
+      GNUNET_free (s);
+      delay = GNUNET_TIME_randomized_backoff (delay,
+                                              GNUNET_TIME_UNIT_SECONDS);
+      task = GNUNET_SCHEDULER_add_delayed (delay,
+                                           &run_shard,
+                                           NULL);
+      return;
+    }
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                "Failed to begin shard (%d)!\n",
+                qs);
+    GNUNET_break (GNUNET_DB_STATUS_HARD_ERROR != qs);
+    global_ret = EXIT_FAILURE;
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
+  if (GNUNET_TIME_absolute_is_future (s->shard_end))
+  {
+    task = GNUNET_SCHEDULER_add_at (s->shard_end,
+                                    &run_shard,
+                                    NULL);
+    abort_shard (s);
+    return;
+  }
+  /* If this is a first-time run, we immediately
+     try to catch up with the present */
+  if (GNUNET_TIME_absolute_is_zero (s->shard_start))
+    s->shard_end = GNUNET_TIME_absolute_get ();
+
+  GNUNET_log (GNUNET_ERROR_TYPE_INFO,
+              "Starting shard [%llu:%llu]!\n",
+              (unsigned long long) s->shard_start.abs_value_us,
+              (unsigned long long) s->shard_end.abs_value_us);
+  task = GNUNET_SCHEDULER_add_now (&run_expire,
+                                   s);
+}
+
+
+/**
+ * First task.
+ *
+ * @param cls closure, NULL
+ * @param args remaining command-line arguments
+ * @param cfgfile name of the configuration file used (for saving, can be NULL!)
+ * @param c configuration
+ */
+static void
+run (void *cls,
+     char *const *args,
+     const char *cfgfile,
+     const struct GNUNET_CONFIGURATION_Handle *c)
+{
+  (void) cls;
+  (void) args;
+  (void) cfgfile;
+
+  cfg = c;
+  if (GNUNET_OK != parse_expire_config ())
+  {
+    cfg = NULL;
+    global_ret = EXIT_NOTCONFIGURED;
+    return;
+  }
+  if (GNUNET_OK !=
+      GNUNET_CONFIGURATION_get_value_time (cfg,
+                                           "exchange",
+                                           "EXPIRE_SHARD_SIZE",
+                                           &shard_size))
+  {
+    cfg = NULL;
+    global_ret = EXIT_NOTCONFIGURED;
+    return;
+  }
+  GNUNET_assert (NULL == task);
+  task = GNUNET_SCHEDULER_add_now (&run_shard,
+                                   NULL);
+  GNUNET_SCHEDULER_add_shutdown (&shutdown_task,
+                                 cls);
+}
+
+
+/**
+ * The main function of the taler-exchange-expire.
+ *
+ * @param argc number of arguments from the command line
+ * @param argv command line arguments
+ * @return 0 ok, non-zero on error, see #global_ret
+ */
+int
+main (int argc,
+      char *const *argv)
+{
+  struct GNUNET_GETOPT_CommandLineOption options[] = {
+    GNUNET_GETOPT_option_timetravel ('T',
+                                     "timetravel"),
+    GNUNET_GETOPT_option_flag ('t',
+                               "test",
+                               "run in test mode and exit when idle",
+                               &test_mode),
+    GNUNET_GETOPT_OPTION_END
+  };
+  enum GNUNET_GenericReturnValue ret;
+
+  if (GNUNET_OK !=
+      GNUNET_STRINGS_get_utf8_args (argc, argv,
+                                    &argc, &argv))
+    return EXIT_INVALIDARGUMENT;
+  TALER_OS_init ();
+  ret = GNUNET_PROGRAM_run (
+    argc, argv,
+    "taler-exchange-expire",
+    gettext_noop (
+      "background process that expires purses"),
+    options,
+    &run, NULL);
+  GNUNET_free_nz ((void *) argv);
+  if (GNUNET_SYSERR == ret)
+    return EXIT_INVALIDARGUMENT;
+  if (GNUNET_NO == ret)
+    return EXIT_SUCCESS;
+  return global_ret;
+}
+
+
+/* end of taler-exchange-expire.c */

src/exchange/taler-exchange-router.c

@@ -17,8 +17,7 @@
 /**
  * @file taler-exchange-router.c
  * @brief Process that routes P2P payments. Responsible for
- *   (1) refunding coins in unmerged purses, (2) merging purses into local reserves;
- *   (3) aggregating remote payments into the respective wad transfers.
+ *   aggregating remote payments into the respective wad transfers.
  *   Execution of actual wad transfers is still to be done by taler-exchange-transfer,
  *   and watching for incoming wad transfers is done by taler-exchange-wirewatch.
  * @author Christian Grothoff

src/exchangedb/plugin_exchangedb_postgres.c

@@ -13554,6 +13554,25 @@ postgres_insert_purse_request (
 }
 
 
+/**
+ * Function called to clean up one expired purse.
+ *
+ * @param cls the @e cls of this struct with the plugin-specific state
+ * @param start_time select purse expired after this time
+ * @param end_time select purse expired before this time
+ * @return transaction status code (#GNUNET_DB_STATUS_SUCCESS_NO_RESULTS if no purse expired in the given time interval).
+ */
+static enum GNUNET_DB_QueryStatus
+postgres_expire_purse (
+  void *cls,
+  struct GNUNET_TIME_Absolute start_time,
+  struct GNUNET_TIME_Absolute end_time)
+{
+  GNUNET_break (0);
+  return GNUNET_DB_STATUS_HARD_ERROR;
+}
+
+
 /**
  * Function called to obtain information about a purse.
  *
@@ -14283,6 +14302,8 @@ libtaler_plugin_exchangedb_postgres_init (void *cls)
     = &postgres_insert_purse_request;
   plugin->select_purse_request
     = &postgres_select_purse_request;
+  plugin->expire_purse
+    = &postgres_expire_purse;
   plugin->select_purse
     = &postgres_select_purse;
   plugin->select_purse_by_merge_pub

src/include/taler_exchangedb_plugin.h

@@ -4603,6 +4603,21 @@ struct TALER_EXCHANGEDB_Plugin
     bool *in_conflict);
 
 
+  /**
+   * Function called to clean up one expired purse.
+   *
+   * @param cls the @e cls of this struct with the plugin-specific state
+   * @param start_time select purse expired after this time
+   * @param end_time select purse expired before this time
+   * @return transaction status code (#GNUNET_DB_STATUS_SUCCESS_NO_RESULTS if no purse expired in the given time interval).
+   */
+  enum GNUNET_DB_QueryStatus
+  (*expire_purse)(
+    void *cls,
+    struct GNUNET_TIME_Absolute start_time,
+    struct GNUNET_TIME_Absolute end_time);
+
+
   /**
    * Function called to obtain information about a purse.
    *