MySQL Bugs: #40355: RESET MASTER causes slave(s) to hang with no message

Bug #40355	RESET MASTER causes slave(s) to hang with no message
Submitted:	27 Oct 2008 18:45	Modified:	27 Oct 2008 18:51
Reporter:	Sven Sandberg	Email Updates:
Status:	Not a Bug	Impact on me:	None
Category:	MySQL Server: Replication	Severity:	S2 (Serious)
Version:	5.1+	OS:	Any
Assigned to:		CPU Architecture:	Any
Tags:	RESET MASTER

Description:
RESET MASTER removes the binlog files without informing any running dump thread(s) about it. That causes running slaves to hang.

How to repeat:
==== BEGIN TEST CASE ====
source include/master-slave.inc;

CREATE TABLE t1 (a INT);

sync_slave_with_master;
connection master;

reset master;
INSERT INTO t1 VALUES (1);

connection slave;
query_vertical SHOW SLAVE STATUS;

connection master;
query_vertical SHOW MASTER STATUS;
sync_slave_with_master;

SELECT * FROM t1;

exit;
==== END TEST CASE ====

The test case fails on the second sync_with_master. The previous call to SHOW SLAVE STATUS shows that Slave_IO_Running = Yes and Slave_SQL_Running = Yes.

Suggested fix:
One of:
 - Document as a (probably unwanted) side effect of running RESET MASTER when there are running slaves.
 - Make the dump threads send some sort of end-of-file message when RESET MASTER is executed.

This is not a bug, because RESET MASTER is not supposed to work when there are running slaves.

See BUG#40361