[ic] IC hanging whilst waiting for external responses

Sam Phillips samp at webmaint.com
Wed Jan 4 07:09:20 EST 2006

Dear all,

We run a site that communicates with external APIs to search details of
flight and accommodation availability to build holiday packages online.

Because of the necessity for up-to-date information and the variety of
searches that are performed, we perform all searches and API requests live.

Recently, the site has started being unresponsive when traffic volume is
high. Our testing seems to show that all available page servers are
being tied up waiting for responses, and because they are not 'busy',
further instances are not being spawned.

A stop gap solution has to be set the StartServers directive at a high
value - for the last few weeks, we've been running at 50, just inside
the maximum allowed range. However, even this many instances isn't
managing to cope with demand, and the site is becoming unresponsive at
busy periods.

Has anyone got any ideas on how we might better configure the IC setup
for this site? Ideally, we would like to spawn more instances as they
are required, to keep pace with demand on the site. These would be
limited by the MaxServers directive so that it didn't run out of
control, as well as the other housekeeping functions of rpc.

Our current traffic settings are (running on rpc):

ifdef TRAFFIC =~ /rpc/i
Message RPC traffic settings.
PreFork             Yes
StartServers        50
MaxServers          300
MaxRequestsPerChild 100
ChildLife           30 minutes
HouseKeeping        2
PIDcheck            120

Many Thanks,

Sam Phillips

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