On Wed, Jun 25, 2014 at 8:52 AM, Robin Becker <ro...@reportlab.com> wrote:
> An apache 2.2 mpm prefork site which uses an external mod_fastcgi socket > to django was experiencing slowdowns during a busy period. > > The main symptom seemed to be a connection delay of up to 10 seconds. > > At the time I saw the machine was not heavily loaded in cpu or memory, but > there were a large number of apache processes; stupidly I didn't think to > count them. > > Later I looked for an error message related to MaxClients exceeded or > similar, but could not see any. > It only appears once per generation, so it might have been days before you noticed the symptom. (Generation: each fresh start or restart of the server is a generation. This can be viewed from mod_status.) > I have upped the MaxClients setting from 150 to 300 and in another busy > period don't see the slowdown although monitoring the apache process count > shows it can exceed the old limit. > > The django side of this is not especially fast and the single socket > connection seems like it might be a choke point, but my understanding is > that the django side of the fastcgi is also spawning children to handle the > requests. > > What are the effects of MaxClient limit being exceeded? delays in processing new connections depending on load and MaxClients and ListenBacklogs, some new connections might even get rejected > Should I have seen an error message if it was exceeded? once per generation --/-- It can be useful to log the response time in microseconds (%D in log format) in order to distinguish delays in the application (delay is reflected in value for %D) from delays before httpd starts processing it due to capacity tuning (delay not reflected in value for %D since it happened before processing started) > -- > Robin Becker > > --------------------------------------------------------------------- > To unsubscribe, e-mail: users-unsubscr...@httpd.apache.org > For additional commands, e-mail: users-h...@httpd.apache.org > > -- Born in Roswell... married an alien... http://emptyhammock.com/ http://edjective.org/
