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MDEV-7888, MDEV-7929: Parallel replication hangs sometimes on ANALYZE TABLE or DDL

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The hangs occur when the group_commit_orderer object is freed before the last
mark_start_commit() call on it - this loses the wakeup to other waiting worker
threads, causing them to hang until killed manually.

The object was freed because wakeup_subsequent_commits() was called two early
in two places. For MDEV-7888, during ANALYZE TABLE, and for MDEV-7929 during
record_gtid() after processing a DDL event. The group_commit_orderer object
can be freed when its last transaction has called wait_for_prior_commit().

Fix by implementing a suspend/resume mechanism for wakeup_subsequent_commits()
that can be used in places where a transaction is committed without this being
the commit of the actual replication event group.

Also add a protection mechanism (that asserts in debug builds) which can
prevent the too-early free and hang if other similar bugs should remain in
other parts of the code.
This commit is contained in:
Kristian Nielsen
2015-04-08 11:01:18 +02:00
parent 880f2273fd
commit 3b961347db
7 changed files with 231 additions and 3 deletions
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14
sql/sql_admin.cc
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@ -320,6 +320,7 @@ static bool mysql_admin_table(THD* thd, TABLE_LIST* tables,
int result_code;
int compl_result_code;
bool need_repair_or_alter= 0;
wait_for_commit* suspended_wfc;
DBUG_ENTER("mysql_admin_table");
DBUG_PRINT("enter", ("extra_open_options: %u", extra_open_options));
@ -337,6 +338,13 @@ static bool mysql_admin_table(THD* thd, TABLE_LIST* tables,
Protocol::SEND_NUM_ROWS | Protocol::SEND_EOF))
DBUG_RETURN(TRUE);
/*
This function calls trans_commit() during its operation, but that does not
imply that the operation is complete or binlogged. So we have to suspend
temporarily the wakeup_subsequent_commits() calls (if used).
*/
suspended_wfc= thd->suspend_subsequent_commits();
mysql_ha_rm_tables(thd, tables);
/*
@ -464,7 +472,7 @@ static bool mysql_admin_table(THD* thd, TABLE_LIST* tables,
if (!table->table->part_info)
{
my_error(ER_PARTITION_MGMT_ON_NONPARTITIONED, MYF(0));
DBUG_RETURN(TRUE);
goto err2;
}
if (set_part_state(alter_info, table->table->part_info, PART_ADMIN))
{
@ -1045,6 +1053,8 @@ send_result_message:
}
my_eof(thd);
thd->resume_subsequent_commits(suspended_wfc);
DBUG_EXECUTE_IF("inject_analyze_table_sleep", my_sleep(500000););
DBUG_RETURN(FALSE);
err:
@ -1058,6 +1068,8 @@ err:
}
close_thread_tables(thd); // Shouldn't be needed
thd->mdl_context.release_transactional_locks();
err2:
thd->resume_subsequent_commits(suspended_wfc);
DBUG_RETURN(TRUE);
}