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Re: mysql strangeness...




Hello Chris,

Can pls you share the below command output...

> SHOW STATUS LIKE 'Threads%';
> SELECT @@thread_cache_size, @@net_buffer_length, @@max_allowed_packet;

What about the limits.conf config on operating system level?

-- WB, MySQL Oracle ACE

> Em 07/12/2014, às 20:03, "Chris Knipe" <savage@xxxxxxxxxxxxx> escreveu:
> 
> FYI - just an example...
> 
> mysql> SELECT VERSION();
> ERROR 2006 (HY000): MySQL server has gone away
> No connection. Trying to reconnect...
> Connection id:    203720459
> Current database: NNTP
> 
> +-----------------------------+
> | VERSION()                   |
> +-----------------------------+
> | 5.5.38-0ubuntu0.12.04.1-log |
> +-----------------------------+
> 1 row in set (33.94 sec)
> 
> 
> mysql> SELECT VERSION();
> +-----------------------------+
> | VERSION()                   |
> +-----------------------------+
> | 5.5.38-0ubuntu0.12.04.1-log |
> +-----------------------------+
> 1 row in set (0.00 sec)
> 
> 
> This is from the mysql client running on the same host as the mysql server,
> connected to localhost via TCP.  Current connections to the DB was at about
> 200 out of 500
> 
> --
> Chris.
> 
> 
> 
> -----Original Message-----
> From: Chris Knipe [mailto:savage@xxxxxxxxxxxxx] 
> Sent: Sunday, December 07, 2014 11:34 PM
> To: 'mysql@xxxxxxxxxxxxxxx'
> Subject: mysql strangeness...
> 
> 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.
> 
> 
> 
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