MDEV-35465 Async replication stops working on Galera async replica no…

…de when parallel replication is enabled

Parallel slave failed to retry in retry_event_group() with error

    WSREP: Parallel slave worker failed at wsrep_before_command() hook

Fix wsrep transaction cleanup/restart in retry_event_group() to properly
clean up previous transaction by calling wsrep_after_statement().
Also move call to reset error after call to wsrep_after_statement()
to make sure that it remains effective.

Add a MTR test galera_as_slave_parallel_retry to reproduce the error
when the fix is not present.

Other issues which were detected when testing with sysbench:

Check if parallel slave is killed for retry before waiting for prior
commits in THD::wsrep_parallel_slave_wait_for_prior_commit(). This
is required with slave-parallel-mode=optimistic to avoid deadlock
when a slave later in commit order manages to reach prepare phase
before a lock conflict is detected.

Suppress wsrep applier specific warning for slave threads.

mysql-test/suite/galera/r/galera_as_slave_parallel_retry.result

@@ -0,0 +1,22 @@
+connection node_2;
+connection node_1;
+connect master, 127.0.0.1, root, , test, $NODE_MYPORT_3;
+connect node_1_ctrl, 127.0.0.1, root, , test, $NODE_MYPORT_1;
+connection node_1;
+START SLAVE;
+connection master;
+CREATE TABLE t1 (f1 INT PRIMARY KEY) ENGINE=InnoDB;
+connection node_1;
+SET GLOBAL debug_dbug = '+d,rpl_parallel_simulate_temp_err_xid,sync.wsrep_retry_event_group';
+connection master;
+INSERT INTO t1 VALUES (1);
+connection node_1_ctrl;
+SET debug_sync = 'now WAIT_FOR sync.wsrep_retry_event_group_reached';
+SET GLOBAL debug_dbug = '';
+SET debug_sync = 'now SIGNAL signal.wsrep_retry_event_group';
+connection node_1;
+SET debug_sync = 'RESET';
+connection master;
+DROP TABLE t1;
+connection node_1;
+STOP SLAVE;

mysql-test/suite/galera/t/galera_as_slave_parallel_retry.cnf

@@ -0,0 +1,10 @@
+!include ../galera_2nodes_as_slave.cnf
+
+[mysqld]
+log-bin=mysqld-bin
+log-slave-updates
+binlog-format=ROW
+
+[mysqld.1]
+slave-parallel-threads=2
+slave-parallel-mode=optimistic

mysql-test/suite/galera/t/galera_as_slave_parallel_retry.test

@@ -0,0 +1,52 @@
+# MDEV-35465 Async replication stops working on Galera async replica node
+# when parallel replication is enabled
+
+--source include/have_innodb.inc
+--source include/have_log_bin.inc
+--source include/galera_cluster.inc
+--source include/have_debug_sync.inc
+
+# Node 3 is not a Galera node, use it as a master
+--connect master, 127.0.0.1, root, , test, $NODE_MYPORT_3
+--connect node_1_ctrl, 127.0.0.1, root, , test, $NODE_MYPORT_1
+
+--connection node_1
+--disable_query_log
+--eval CHANGE MASTER TO MASTER_HOST='127.0.0.1', MASTER_USER='root', MASTER_PORT=$NODE_MYPORT_3;
+--enable_query_log
+START SLAVE;
+
+--connection master
+CREATE TABLE t1 (f1 INT PRIMARY KEY) ENGINE=InnoDB;
+
+--connection node_1
+--let $wait_condition = SELECT COUNT(*) = 1 FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 't1'
+--source include/wait_condition.inc
+
+#
+--let debug_dbug_orig = `SELECT @@GLOBAL.debug_dbug`
+SET GLOBAL debug_dbug = '+d,rpl_parallel_simulate_temp_err_xid,sync.wsrep_retry_event_group';
+
+--connection master
+INSERT INTO t1 VALUES (1);
+
+--connection node_1_ctrl
+SET debug_sync = 'now WAIT_FOR sync.wsrep_retry_event_group_reached';
+--eval SET GLOBAL debug_dbug = '$debug_dbug_orig'
+SET debug_sync = 'now SIGNAL signal.wsrep_retry_event_group';
+
+--let $wait_condition = SELECT COUNT(*) = 1 FROM t1;
+--source include/wait_condition.inc
+
+
+--connection node_1
+SET debug_sync = 'RESET';
+
+--connection master
+DROP TABLE t1;
+
+--connection node_1
+--let $wait_condition = SELECT COUNT(*) = 0 FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME = 't1'
+--source include/wait_condition.inc
+
+STOP SLAVE;

sql/log_event_server.cc

@@ -5511,7 +5511,7 @@ int Rows_log_event::do_apply_event(rpl_group_info *rgi)
     if (unlikely(open_and_lock_tables(thd, rgi->tables_to_lock, FALSE, 0)))
     {
 #ifdef WITH_WSREP
-      if (WSREP(thd))
+      if (WSREP(thd) && !thd->slave_thread)
       {
         WSREP_WARN("BF applier thread=%lu failed to open_and_lock_tables for "
                    "%s, fatal: %d "

sql/rpl_parallel.cc

@@ -134,7 +134,7 @@ handle_queued_pos_update(THD *thd, rpl_parallel_thread::queued_event *qev)
   asynchronously, we need to be sure they will be completed before starting a
   new transaction. Otherwise the new transaction might suffer a spurious kill.
 */
-static void
+void
 wait_for_pending_deadlock_kill(THD *thd, rpl_group_info *rgi)
 {
   PSI_stage_info old_stage;
@@ -831,8 +831,12 @@ retry_event_group(rpl_group_info *rgi, rpl_parallel_thread *rpt,
   err= 0;
   errmsg= NULL;
 #ifdef WITH_WSREP
-  thd->wsrep_cs().reset_error();
-  WSREP_DEBUG("retrying async replication event");
+  DBUG_EXECUTE_IF("sync.wsrep_retry_event_group", {
+    const char act[]= "now "
+                      "SIGNAL sync.wsrep_retry_event_group_reached "
+                      "WAIT_FOR signal.wsrep_retry_event_group";
+    debug_sync_set_action(thd, STRING_WITH_LEN(act));
+  };);
 #endif /* WITH_WSREP */
 
   /*
@@ -981,15 +985,20 @@ retry_event_group(rpl_group_info *rgi, rpl_parallel_thread *rpt,
   */
   thd->reset_killed();
 #ifdef WITH_WSREP
-  if (wsrep_before_command(thd))
+  if (WSREP(thd))
   {
-    WSREP_WARN("Parallel slave worker failed at wsrep_before_command() hook");
-    err= 1;
-    goto err;
+    /* Exec after statement hook to make sure that the failed transaction
+     * gets cleared and reset error state. */
+    if (wsrep_after_statement(thd))
+    {
+      WSREP_WARN("Parallel slave worker failed at wsrep_after_statement() hook");
+      err= 1;
+      goto err;
+    }
+    thd->wsrep_cs().reset_error();
+    wsrep_start_trx_if_not_started(thd);
+    WSREP_DEBUG("parallel slave retry, after trx start");
   }
-  wsrep_start_trx_if_not_started(thd);
-  WSREP_DEBUG("parallel slave retry, after trx start");
-
 #endif /* WITH_WSREP */
   strmake_buf(log_name, ir->name);
   if ((fd= open_binlog(&rlog, log_name, &errmsg)) <0)

sql/rpl_parallel.h

@@ -380,6 +380,7 @@ struct rpl_parallel {
 extern struct rpl_parallel_thread_pool global_rpl_thread_pool;
 
 
+extern void wait_for_pending_deadlock_kill(THD *thd, rpl_group_info *rgi);
 extern int rpl_parallel_resize_pool_if_no_slaves(void);
 extern int rpl_parallel_activate_pool(rpl_parallel_thread_pool *pool);
 extern int rpl_parallel_inactivate_pool(rpl_parallel_thread_pool *pool);

sql/wsrep_mysqld.cc

@@ -3426,11 +3426,16 @@ enum wsrep::streaming_context::fragment_unit wsrep_fragment_unit(ulong unit)
 
 bool THD::wsrep_parallel_slave_wait_for_prior_commit()
 {
-  if (rgi_slave && rgi_slave->is_parallel_exec && wait_for_prior_commit())
+  if (rgi_slave && rgi_slave->is_parallel_exec)
   {
-    return 1;
+    wait_for_pending_deadlock_kill(this, rgi_slave);
+    if (rgi_slave->killed_for_retry) {
+      my_error(ER_LOCK_DEADLOCK, MYF(0));
+      return true;
+    }
+    return wait_for_prior_commit();
   }
-  return 0;
+  return false;
 }
 
 /***** callbacks for wsrep service ************/