Monday, March 5, 2012
MySQL can ignore --relay-log-space-limit
Do you have replication slaves that ignore --relay-log-space-limit? This bug has been open for a while on the bug system that isn't http://bugs.mysql.com. I was forced to fix it myself to avert a mutiny. I am amused that the variable named ignore_log_space_limit is part of the problem.
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I used this option recently to prevent saturation of disk space but I have not found any problems so far.
ReplyDeleteThis is "funny" that pt-variable-advisor says "Setting relay_log_space_limit is relatively rare, and could cause an increased risk of previously unknown bugs in replication" about this option...
I've seen bugs in the past with relay_log_space, including infinite loops in relay log fetching: suddenly the server would start fetching a single log from the master over and over again, filling up disk space in a matter of minutes (and ignoring the space limit!). These bugs were probably fixed in the late 5.0 series, though. We should update the advice in the pt-variable-advisor rule to mention the other concern, which is that if you're relying on a replica to have a copy of the master's logs for crash recovery, it may have stopped fetching due to the space limit and not have recent transactions.
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