http://maggienelson.com/2008/08/to-persist-or-not-to-persist/ databases and code goodness Thu, 28 Jan 2010 22:17:15 -0500 http://wordpress.org/?v=2.8.4 hourly 1 http://maggienelson.com/2008/08/to-persist-or-not-to-persist/comment-page-1/#comment-29 M. van der Klip Fri, 22 Aug 2008 10:35:30 +0000 http://maggienelson.com/blog/?p=43#comment-29 Actually, I'd say it depends on the use case. We're running some ad delivery software which does about 2k inserts per second at peak times. We have been running this without persistent connections for a long time under Apache. We had long learned that enabling persistent connections under Apache is a no-go. However when we made the switch from Apache to lighttpd several years ago, we got loads more control of the number of running PHP processes. Previously we were running hundreds of Apache processes on one single webserver, which got replaced by one single lighttpd process and a fixed amount of 20 PHP FastCGI processes. Recently we decided to evaluate persistent connections again because we realized that the math had became easy: servers * 20 = max_connections. The number of connections to our MySQL server is now constant and the system load has gone down by about 20%. Actually, I’d say it depends on the use case. We’re running some ad delivery software which does about 2k inserts per second at peak times. We have been running this without persistent connections for a long time under Apache. We had long learned that enabling persistent connections under Apache is a no-go.
However when we made the switch from Apache to lighttpd several years ago, we got loads more control of the number of running PHP processes. Previously we were running hundreds of Apache processes on one single webserver, which got replaced by one single lighttpd process and a fixed amount of 20 PHP FastCGI processes.
Recently we decided to evaluate persistent connections again because we realized that the math had became easy: servers * 20 = max_connections. The number of connections to our MySQL server is now constant and the system load has gone down by about 20%.

]]> http://maggienelson.com/2008/08/to-persist-or-not-to-persist/comment-page-1/#comment-28 Daniel Smith Fri, 22 Aug 2008 08:30:25 +0000 http://maggienelson.com/blog/?p=43#comment-28 Maggie, Don't forget that with persistent connections, MySQL won't know to drop temporary tables if you use them in the connection. It's bit me in the past. Good luck making your decision! Daniel Maggie,
Don’t forget that with persistent connections, MySQL won’t know to drop temporary tables if you use them in the connection. It’s bit me in the past. Good luck making your decision!
Daniel

]]> http://maggienelson.com/2008/08/to-persist-or-not-to-persist/comment-page-1/#comment-27 Carsten Pedersen Fri, 22 Aug 2008 08:19:17 +0000 http://maggienelson.com/blog/?p=43#comment-27 Good run-down of the issues and documentation available. I've been teaching "don't bother with persistent connections" for years, but haven't had a good source. Now I do. Thanks! Good run-down of the issues and documentation available. I’ve been teaching “don’t bother with persistent connections” for years, but haven’t had a good source. Now I do. Thanks!

]]> http://maggienelson.com/2008/08/to-persist-or-not-to-persist/comment-page-1/#comment-26 Richard Harrison Thu, 21 Aug 2008 21:58:11 +0000 http://maggienelson.com/blog/?p=43#comment-26 My experience with persistent connections is from years ago (circa 2001) but the problem we found was that on a very busy server the Apache processes would get so numerous that they would suck up all of the available MySQL connections and then the next Apache process was screwed because it's connection would then get refused. This was mostly because Apache was used to serve all static content, so a process serving a static image would still have it's own persistent connection. My experience with persistent connections is from years ago (circa 2001) but the problem we found was that on a very busy server the Apache processes would get so numerous that they would suck up all of the available MySQL connections and then the next Apache process was screwed because it’s connection would then get refused.
This was mostly because Apache was used to serve all static content, so a process serving a static image would still have it’s own persistent connection.

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