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.
The only way to not acquire the query cache mutex in My SQL pre-5.5 is to compile My SQL without query cache. For My SQL 5.5 , to completely disable the query cache (thus, not acquiring the query cache mutex) is required to set query_cache_type=OFF at startup (not at runtime).
For example, the position is 999 and I want to analyze the previous five events. Q: We are having issues with inconsistencies over time.
We also have a lot of “waiting for table lock” statuses during high volume usage.
I see mysql cranking away with 99% CPU usage, whereas when I use statement-based replication it is decidely IO bound, with barely any CPU usage that isn't IO wait.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.So, the jumpy behaviour is caused by not using a global timestamp for replication delay, but simply the delay behind the last "hop" in the replication chain.We found this severely annoying and now use My SQL's event scheduler to update a timer table on each master every second, so we can actually see actual delay from the global master (in a non-ring topology) or delay from any peer in a ring.