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MDEV-30780 optimistic parallel slave hangs after hit an error

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The hang could be seen as show slave status displaying an error like
    Last_Error: Could not execute Write_rows_v1
along with
    Slave_SQL_Running: Yes

accompanied with one of the replication threads in show-processlist
characteristically having status like

   2394 | system user  |    | NULL | Slave_worker | 50852| closing tables

It turns out that closing tables worker got entrapped in endless looping
in mark_start_commit_inner() across already garbage-collected gco items.

The reclaimed gco links are explained with actually possible
out-of-order groups of events termination due to the Last_Error.
This patch reinforces the correct ordering to perform
finish_event_group's cleanup actions, incl unlinking gco:s
from the active list.
This commit is contained in:
Andrei
2023-03-05 15:12:13 +02:00
parent dfdcd7ffab
commit d4339620be
5 changed files with 299 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

38
sql/rpl_parallel.cc
View File

@ -261,6 +261,12 @@ finish_event_group(rpl_parallel_thread *rpt, uint64 sub_id,
STRING_WITH_LEN("now WAIT_FOR proceed_by_1000"));
}
});
DBUG_EXECUTE_IF("hold_worker2_favor_worker3", {
if (rgi->current_gtid.seq_no == 2001) {
DBUG_ASSERT(!rgi->worker_error || entry->stop_on_error_sub_id == sub_id);
debug_sync_set_action(thd, STRING_WITH_LEN("now SIGNAL cont_worker3"));
}
});
#endif
if (rgi->killed_for_retry == rpl_group_info::RETRY_KILL_PENDING)
@ -284,6 +290,11 @@ signal_error_to_sql_driver_thread(THD *thd, rpl_group_info *rgi, int err)
In case we get an error during commit, inform following transactions that
we aborted our commit.
*/
DBUG_EXECUTE_IF("hold_worker2_favor_worker3", {
if (rgi->current_gtid.seq_no == 2002) {
debug_sync_set_action(thd, STRING_WITH_LEN("now WAIT_FOR cont_worker2"));
}});
rgi->unmark_start_commit();
rgi->cleanup_context(thd, true);
rgi->rli->abort_slave= true;
@ -788,7 +799,14 @@ do_retry:
thd->reset_killed();
thd->clear_error();
rgi->killed_for_retry = rpl_group_info::RETRY_KILL_NONE;
#ifdef ENABLED_DEBUG_SYNC
DBUG_EXECUTE_IF("hold_worker2_favor_worker3", {
if (rgi->current_gtid.seq_no == 2003) {
debug_sync_set_action(thd,
STRING_WITH_LEN("now WAIT_FOR cont_worker3"));
}
});
#endif
/*
If we retry due to a deadlock kill that occurred during the commit step, we
might have already updated (but not committed) an update of table
@ -806,15 +824,12 @@ do_retry:
for (;;)
{
mysql_mutex_lock(&entry->LOCK_parallel_entry);
if (entry->stop_on_error_sub_id == (uint64) ULONGLONG_MAX ||
register_wait_for_prior_event_group_commit(rgi, entry);
if (!(entry->stop_on_error_sub_id == (uint64) ULONGLONG_MAX ||
#ifndef DBUG_OFF
(DBUG_EVALUATE_IF("simulate_mdev_12746", 1, 0)) ||
(DBUG_EVALUATE_IF("simulate_mdev_12746", 1, 0)) ||
#endif
rgi->gtid_sub_id < entry->stop_on_error_sub_id)
{
register_wait_for_prior_event_group_commit(rgi, entry);
}
else
rgi->gtid_sub_id < entry->stop_on_error_sub_id))
{
/*
A failure of a preceeding "parent" transaction may not be
@ -1991,6 +2006,9 @@ rpl_parallel_thread::get_gco(uint64 wait_count, group_commit_orderer *prev,
gco->prior_sub_id= prior_sub_id;
gco->installed= false;
gco->flags= 0;
#ifndef DBUG_OFF
gco->gc_done= false;
#endif
return gco;
}
@ -1998,6 +2016,10 @@ rpl_parallel_thread::get_gco(uint64 wait_count, group_commit_orderer *prev,
void
rpl_parallel_thread::loc_free_gco(group_commit_orderer *gco)
{
#ifndef DBUG_OFF
DBUG_ASSERT(!gco->gc_done);
gco->gc_done= true;
#endif
if (!loc_gco_list)
loc_gco_last_ptr_ptr= &gco->next_gco;
else