MySQL Bugs: #79: relay_log_space_limit can cause deadlock if we have a big transaction

Bug #79	relay_log_space_limit can cause deadlock if we have a big transaction
Submitted:	16 Feb 2003 10:44	Modified:	17 Mar 2003 14:08
Reporter:	Guilhem Bichot	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Replication	Severity:	S3 (Non-critical)
Version:	4.0	OS:	Any (all)
Assigned to:	Guilhem Bichot	CPU Architecture:	Any

Description:
When using the relay_log_space_limit (undocumented) option, the I/O slave thread will block if the cumulative size of relay logs exceeds relay_log_space_limit ; but this can cause a deadlock if the SQL slave thread is executing a transaction, and cannot free the space because the COMMIT is not in the relay log (and it will never be as the I/O thread is blocked).

How to repeat:
InnoDB
+ 1MB transaction on the master
+ relay_log_space_limit=1024 on the slave
Then do :
START SLAVE
The replication does not make any progress, and it's impossible to STOP SLAVE.
Only 'kill -9' works.

Suggested fix:
I have a patch, will send it with other patches (for #52, #53 and #70).
-- 
   __  ___     ___ ____  __
  /  |/  /_ __/ __/ __ \/ /    Mr. Guilhem Bichot <guilhem@mysql.com>
 / /|_/ / // /\ \/ /_/ / /__   MySQL AB, Full-Time Software Developer
/_/  /_/\_, /___/\___\_\___/   Bordeaux, France
       <___/   www.mysql.com   +33 5 56 88 34 39

need a bit of time to finish the patch (same as #53)

It is non-critical as it happens only when one uses --relay_log_space_limit which is undocumented. Will be fixed in 4.0 some day (I have a patch but it's low priority).

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