lib-sql: mysql - Keep a persistent cache of used sql databases

Currently we don't really need to support freeing databases. If needed,
this could be done with e.g. freeing unused databases after N seconds
of idling.

diff --git a/src/lib-sql/driver-mysql.c b/src/lib-sql/driver-mysql.c
index 9139bc9c00f8cc0679b6b4ae5948f0c4b012b2bd..54aa0909e4a978628dbf9c222d8444322f798b79 100644 (file)
--- a/src/lib-sql/driver-mysql.c
+++ b/src/lib-sql/driver-mysql.c
@@ -153,10 +153,20 @@ struct mysql_transaction_context {
        bool commit_started:1;
 };
 
+struct mysql_db_cache {
+       /* Contains the sqlpool connection */
+       struct sql_db *db;
+
+       const struct mysql_settings *set;
+       const struct ssl_settings *ssl_set;
+};
+
 extern const struct sql_db driver_mysql_db;
 extern const struct sql_result driver_mysql_result;
 extern const struct sql_result driver_mysql_error_result;
 
+static ARRAY(struct mysql_db_cache) mysql_db_cache;
+
 static struct event_category event_category_mysql = {
        .parent = &event_category_sql,
        .name = "mysql"
@@ -390,6 +400,23 @@ driver_mysql_parse_connect_string(pool_t pool, const char *connect_string,
        return 0;
 }
 
+static struct mysql_db_cache *
+driver_mysql_db_cache_find(const struct mysql_settings *set,
+                          const struct ssl_settings *ssl_set)
+{
+       struct mysql_db_cache *cache;
+
+       array_foreach_modifiable(&mysql_db_cache, cache) {
+               if (settings_equal(&mysql_setting_parser_info,
+                                  set, cache->set, NULL) &&
+                   (!set->ssl ||
+                    settings_equal(&ssl_setting_parser_info,
+                                   ssl_set, cache->ssl_set, NULL)))
+                       return cache;
+       }
+       return NULL;
+}
+
 static struct sql_db *
 driver_mysql_init_common(pool_t pool, struct event *event_parent,
                         const struct mysql_settings *set,
@@ -461,13 +488,28 @@ driver_mysql_init_v(struct event *event, struct sql_db **db_r,
        }
 
        if (event_get_ptr(event, SQLPOOL_EVENT_PTR) == NULL) {
-               /* Use sqlpool for managing multiple connections */
-               *db_r = driver_sqlpool_init(&driver_mysql_db, event,
-                                           MYSQL_SQLPOOL_SET_NAME,
-                                           &set->sqlpool_hosts,
-                                           set->connection_limit);
-               settings_free(set);
-               settings_free(ssl_set);
+               /* See if there is already such a database */
+               struct mysql_db_cache *cache =
+                       driver_mysql_db_cache_find(set, ssl_set);
+               if (cache != NULL) {
+                       settings_free(set);
+                       settings_free(ssl_set);
+               } else {
+                       /* Use sqlpool for managing multiple connections.
+                          Leave an extra reference to it, so it won't be freed
+                          while it's still in the cache array. */
+                       struct sql_db *db =
+                               driver_sqlpool_init(&driver_mysql_db, event,
+                                                   MYSQL_SQLPOOL_SET_NAME,
+                                                   &set->sqlpool_hosts,
+                                                   set->connection_limit);
+                       cache = array_append_space(&mysql_db_cache);
+                       cache->db = db;
+                       cache->set = set;
+                       cache->ssl_set = ssl_set;
+               }
+               sql_ref(cache->db);
+               *db_r = cache->db;
                return 0;
        }
        /* We're being initialized by sqlpool - create a real mysql
@@ -1020,11 +1062,20 @@ const char *driver_mysql_version = DOVECOT_ABI_VERSION;
 
 void driver_mysql_init(void)
 {
+       i_array_init(&mysql_db_cache, 4);
        sql_driver_register(&driver_mysql_db);
 }
 
 void driver_mysql_deinit(void)
 {
+       struct mysql_db_cache *cache;
+
+       array_foreach_modifiable(&mysql_db_cache, cache) {
+               settings_free(cache->set);
+               settings_free(cache->ssl_set);
+               sql_unref(&cache->db);
+       }
+       array_free(&mysql_db_cache);
        sql_driver_unregister(&driver_mysql_db);
 }