lib-sql: Connect earlier to fallback host when using multiple hosts and primary fails.

diff --git a/src/lib-sql/driver-sqlpool.c b/src/lib-sql/driver-sqlpool.c
index 7bd2af90bb6595dec38df0c9a0e40b99934422dd..237270815220baca49a9f72a1b916400c4d1378c 100644 (file)
--- a/src/lib-sql/driver-sqlpool.c
+++ b/src/lib-sql/driver-sqlpool.c
@@ -70,6 +70,9 @@ struct sqlpool_transaction_context {
 
 extern struct sql_db driver_sqlpool_db;
 
+static struct sqlpool_connection *
+sqlpool_add_connection(struct sqlpool_db *db, struct sqlpool_host *host,
+                      unsigned int host_idx);
 static void
 driver_sqlpool_query_callback(struct sql_result *result,
                              struct sqlpool_request *request);
@@ -172,39 +175,6 @@ static void sqlpool_reconnect(struct sql_db *conndb)
        (void)sql_connect(conndb);
 }
 
-static void
-sqlpool_state_changed(struct sql_db *conndb, enum sql_db_state prev_state,
-                     void *context)
-{
-       struct sqlpool_db *db = context;
-
-       if (conndb->state == SQL_DB_STATE_IDLE) {
-               conndb->connect_failure_count = 0;
-               conndb->connect_delay = SQL_CONNECT_MIN_DELAY;
-               sqlpool_request_send_next(db, conndb);
-       }
-
-       if (prev_state == SQL_DB_STATE_CONNECTING &&
-           conndb->state == SQL_DB_STATE_DISCONNECTED &&
-           !conndb->no_reconnect) {
-               /* connect failed */
-               if (conndb->connect_failure_count > 0) {
-                       /* increase delay between reconnections to this
-                          server */
-                       conndb->connect_delay *= 5;
-                       if (conndb->connect_delay > SQL_CONNECT_MAX_DELAY)
-                               conndb->connect_delay = SQL_CONNECT_MAX_DELAY;
-               }
-               conndb->connect_failure_count++;
-
-               /* reconnect after the delay */
-               if (conndb->to_reconnect != NULL)
-                       timeout_remove(&conndb->to_reconnect);
-               conndb->to_reconnect = timeout_add(conndb->connect_delay * 1000,
-                                                  sqlpool_reconnect, conndb);
-       }
-}
-
 static struct sqlpool_host *
 sqlpool_find_host_with_least_connections(struct sqlpool_db *db,
                                         unsigned int *host_idx_r)
@@ -227,16 +197,72 @@ sqlpool_find_host_with_least_connections(struct sqlpool_db *db,
        return min;
 }
 
-static struct sqlpool_connection *sqlpool_add_connection(struct sqlpool_db *db)
+static bool sqlpool_have_successful_connections(struct sqlpool_db *db)
+{
+       const struct sqlpool_connection *conn;
+
+       array_foreach(&db->all_connections, conn) {
+               if (conn->db->state >= SQL_DB_STATE_IDLE)
+                       return TRUE;
+       }
+       return FALSE;
+}
+
+static void
+sqlpool_handle_connect_failed(struct sqlpool_db *db, struct sql_db *conndb)
 {
-       struct sql_db *conndb;
        struct sqlpool_host *host;
-       struct sqlpool_connection *conn;
        unsigned int host_idx;
 
-       host = sqlpool_find_host_with_least_connections(db, &host_idx);
-       if (host->connection_count >= db->connection_limit)
-               return NULL;
+       if (conndb->connect_failure_count > 0) {
+               /* increase delay between reconnections to this
+                  server */
+               conndb->connect_delay *= 5;
+               if (conndb->connect_delay > SQL_CONNECT_MAX_DELAY)
+                       conndb->connect_delay = SQL_CONNECT_MAX_DELAY;
+       }
+       conndb->connect_failure_count++;
+
+       /* reconnect after the delay */
+       if (conndb->to_reconnect != NULL)
+               timeout_remove(&conndb->to_reconnect);
+       conndb->to_reconnect = timeout_add(conndb->connect_delay * 1000,
+                                          sqlpool_reconnect, conndb);
+
+       /* if we have zero successful hosts and there still are hosts
+          without connections, connect to one of them. */
+       if (!sqlpool_have_successful_connections(db)) {
+               host = sqlpool_find_host_with_least_connections(db, &host_idx);
+               if (host->connection_count == 0)
+                       (void)sqlpool_add_connection(db, host, host_idx);
+       }
+}
+
+static void
+sqlpool_state_changed(struct sql_db *conndb, enum sql_db_state prev_state,
+                     void *context)
+{
+       struct sqlpool_db *db = context;
+
+       if (conndb->state == SQL_DB_STATE_IDLE) {
+               conndb->connect_failure_count = 0;
+               conndb->connect_delay = SQL_CONNECT_MIN_DELAY;
+               sqlpool_request_send_next(db, conndb);
+       }
+
+       if (prev_state == SQL_DB_STATE_CONNECTING &&
+           conndb->state == SQL_DB_STATE_DISCONNECTED &&
+           !conndb->no_reconnect)
+               sqlpool_handle_connect_failed(db, conndb);
+}
+
+static struct sqlpool_connection *
+sqlpool_add_connection(struct sqlpool_db *db, struct sqlpool_host *host,
+                      unsigned int host_idx)
+{
+       struct sql_db *conndb;
+       struct sqlpool_connection *conn;
+
        host->connection_count++;
 
        conndb = db->driver->v.init(host->connect_string);
@@ -252,6 +278,19 @@ static struct sqlpool_connection *sqlpool_add_connection(struct sqlpool_db *db)
        return conn;
 }
 
+static struct sqlpool_connection *
+sqlpool_add_new_connection(struct sqlpool_db *db)
+{
+       struct sqlpool_host *host;
+       unsigned int host_idx;
+
+       host = sqlpool_find_host_with_least_connections(db, &host_idx);
+       if (host->connection_count >= db->connection_limit)
+               return NULL;
+       else
+               return sqlpool_add_connection(db, host, host_idx);
+}
+
 static const struct sqlpool_connection *
 sqlpool_find_available_connection(struct sqlpool_db *db,
                                  unsigned int unwanted_host_idx,
@@ -316,7 +355,7 @@ driver_sqlpool_get_connection(struct sqlpool_db *db,
        }
        if (conn == NULL) {
                /* still nothing. try creating new connections */
-               conn = sqlpool_add_connection(db);
+               conn = sqlpool_add_new_connection(db);
                if (conn == NULL || !SQL_DB_IS_READY(conn->db))
                        return FALSE;
        }
@@ -425,7 +464,7 @@ driver_sqlpool_init(const char *connect_string, const struct sql_db *driver)
 
        i_array_init(&db->all_connections, 16);
        /* always have at least one backend connection initialized */
-       (void)sqlpool_add_connection(db);
+       (void)sqlpool_add_new_connection(db);
        return &db->api;
 }