[wp-hackers] HyperDB seems to be causing an unusual number of PING to the database

[Potkanski, Jason]

The number of pings does not seem to be all that unusual. The CONNECT response time does seems a bit long.

Have you run mysqltuner against your production dbs? See http://blog.mysqltuner.com/ . Extensive Mysql tuning is not for this list. Mysql workbench has some nice realtime graphs as well.

Also, check your DNS server that it isn't overloaded. Replacing the entry with the IP address may save you connect time. 

During a lot of our various "panics" here we always start looking at the database server. The case has always been that the DB server is generally fine, that we had overloaded PHP instances, a poorly written plugin, etc. 

Jason Potkanski
Tribune Technology, Back-End Support

-----Original Message-----
From: wp-hackers-bounces at lists.automattic.com [mailto:wp-hackers-bounces at lists.automattic.com] On Behalf Of dave morris
Sent: Tuesday, January 25, 2011 10:24 AM
To: wp-hackers at lists.automattic.com
Subject: [wp-hackers] HyperDB seems to be causing an unusual number of PING to the database

I am using HyperDB with WordPress 3.0.1, and I have a MySQL network
sniffer setup to log all database traffic. I have a master write db
server and two slave read servers right now.

While analyzing some of the log files the other day, I noticed an
unusual number of PING and CONNECT requests, and I'm wondering if this
may be caused by my HyperDB configuration. Here is an example from the
sniffer logs of a 10 minute period of time. There are 600K+ PING
requests:

# Profile
# Rank Query ID           Response time    Calls  R/Call   Apdx V/M
Item
# ==== ================== ================ ====== ======== ==== =====
====
#    1 0x5D51E5F01B88B79E  1730.0760 78.0%  15216   0.1137 1.00 32...
ADMIN CONNECT
#    2 0x04FE01C5B31FD305    74.5528  3.4% 604880   0.0001 1.00  0.67
ADMIN PING
#    3 0x23C8A0F1ED72D23D    57.2139  2.6%  17758   0.0032 1.00  0.02
SELECT wp_?_posts
#    4 0xE0E902FB71244C1E    41.6918  1.9%   2540   0.0164 1.00  0.09
SELECT wp_?_posts
#    5 0xDAADAC0539F80EE6    27.2083  1.2% 175902   0.0002 1.00  0.00
SELECT wp_sitemeta
...

This happened during a high traffic day, but it's still making me
curious whether I should modify my HyperDB configuration. I have
tcp_responsiveness_check on, and persistent off right now. Could this
be causing the large number of PINGs and CONNECTs?

If I turn on persistent connections and turn off
tcp_responsiveness_check, what other implications will that have on my
current setup?

Thanks for your help,
Dave
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