Hi Guy, On Wed, Oct 27, 2010 at 12:49:16PM -0700, [email protected] wrote: > Hi all, > > We're trying to narrow down the source of delays we're seeing in > response times from our web cluster. Using firebug, we're seeing that > scripts are taking around 10 - 50 ms to complete (we're returning that > in the response data), but the total response time shown by firebug is > anywhere between 100ms all the way up to, in some cases, a couple of > seconds. This also seems to have increased in the recent past.
if you observe randomly spread response times with a background noise looking like stairs at multiple seconds (generally 3 secs), most of the time this is caused by TCP retransmits due to losses anywhere between a client and a server. If your logs report long connect times between haproxy and your servers, then you can spot an issue in your infra. If you are lucky to see long request times (those are rare), sometimes it indicates that a client is having difficulties sending a request after the connection is accepted. If you want to check how your server's response times are seen from haproxy, then halog (in the contrib subdir) can help you. Use it with "-pct" to get a percentile of connect and response times. And the newly released 1.4.9 adds features to report response times by URL in halog. Most of the time, the log files are the starting point, so that you can find where to search and where not to search. Regards, Willy
