Mysql replication invalidating query cache entries
I'm running a 4 servers master-master cluster of My Sql. Replication topology: 1 - 1 UPDATE It seems that server 3 has its SBM at 0, while the other servers are jumping up and down. It looks like the server is busy doing something, and there is a huge delay between when the server gets the statement, and when it executes it. After disabling cache, server 4 is ok but 1&2 are still having this issue. id=60696 If anyone knows how to fix it, i would be glad to hear There is one flaw with mysql's seconds_behind_master value: it only takes into account the position relative to one upstream hop away.
(2 servers version 5.1, and 2 version 5.5) While checking the slave status, i see the seconds_behind_master at 0, and half a second after i see it jumps to 2000, and so fourth. Easiest demonstrated with a slightly simpler replication topology: server1 - server3 If server2 falls behind, and is processing some long-running queries, the following will happen, assuming as start point: : Everyone ok : server1 writes two 10-minute queries to the binlog, no replication delay anywhere : server2 starts processing query one. : server2 is done with query 2, replication delay zero again.
I belive the issue is not related to long running queries.
You should invest more time in understanding the question rather than using your copy&paste skills with a hope that it [email protected] the dead lock "Waiting for query cache lock" is usually coming from write contention on the query cache, because it's too big and mysql spend more time to invalidate that cache, and therefore reducing the size of the cache to the lowest performing value is the way to go.
, mostly INSERT statements, around 5-10 rows per second. In 5-10 seconds when it will be time to process new data again the same lock up will happen. Query #2 is the updating of the post-processed data.
A PHP based application is running on the server that reads the freshly replicated data every 5-10 seconds, processes it and stores (INSERT ON DUPLICATE KEY UPDATE) results in a separate database . A web application displays the post-processed data for the user. Query #3 is streaming (unbuffered) the newly replicated data for processing.
id=38551 In short, in all My SQL versions before 5.5 , the query cache mutex is acquired even if query_cache_size=0 and query_cache_type=OFF : always!
That is, even if the query cache is not enabled, the mutex (slow, by nature) to access the (not existing) query cache is acquired for every binlog event.