Hi, I have a "not so" busy MySQL server (+- 150 Selects/sec, 180 Deletes/Sec, 320 Updates/Sec, 90 Inserts/Sec and 200 Replace/Sec), max 512 concurrent connections.
The server is running on a Dell R720 with 64GB Ram, Xeon E5-2620. Data is on a 4 x 3TB (RAID10) SATA3 array, and binlogs on a 4 x 600GB (RAID10) SSD array. MySQL 5.5.38 Up to a while ago (few days / week), everything was running absolutely fine. Lately however, I have noticed more and more times that I am hitting my max connection limits. Standard tools like mysql-tuner (which took more than an hour to run because of slow connections to MySQL), tuning-primer, innotop, etc. all shows that the configured variables are within normal parameters, and MySQL is also not under *any* IO load what so ever. I'd say 99% of all tables are InnoDB, and even the one single Memory table that I have, seems to be running slow queries :-( I'm also seeing a lot of "connection reset by peer" network related errors. What I am seeing, is that even when there are only like 300 or so connections established to the server, even the mysql (command utility) running on the localhost, takes MINUTES to establish a connection to the mysql server - however, once the connection IS established, queries execute absolutely fine and within seconds. It's just the initial establishment of the connection to mysql which is taking forever. The process list shows 99% of all the active connections in a "READING FROM NET" state (unauthenticated users). Skip-name-resolve and all those things are disabled, and tcpdumps also confirmed that mysql is in fact NOT doing DNS lookups. The server IMHO is under no significant load at all (dedicated mysql system), and there's only +- 5Mbps of traffic on the 1Gbps interface in the server. All in all, graphs indicate 750/800 QPS with about 30% reads, and 70% writes. Can anyone perhaps suggest some things to look into here? I'm pretty sure that the problem is with the initial establishment of the TCP connection to mysql, rather than it being a mysql issue related to queries and what not. Telneting to the mysql socket, I do get the initial greeting from the server virtually instantaneous like it should be. So the only thing that I can think of is that something is whacked in terms of authenticating users? Box is firewalled, only authorised hosts are permitted to connect, all users are authenticating by password and IP (%) -- Chris. -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql
