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From bugzi...@apache.org
Subject [Bug 56308] New: 1 second delay in handle request kills performance for web services
Date Mon, 24 Mar 2014 16:08:19 GMT
https://issues.apache.org/bugzilla/show_bug.cgi?id=56308

            Bug ID: 56308
           Summary: 1 second delay in handle request kills performance for
                    web services
           Product: Apache httpd-2
           Version: 2.5-HEAD
          Hardware: PC
            Status: NEW
          Severity: normal
          Priority: P2
         Component: mod_fcgid
          Assignee: bugs@httpd.apache.org
          Reporter: bmccart@overwatch.textron.com

With batched requests (i.e. loading 35 dynamically generated image tiles)
mod_fcgid if it has fewer process-nodes than connections processes the last N
requests at 1 per second.  (Where N is the number of connections greater than
number of process-nodes.)

This scenario can be observed with a simple test web page that makes a group of
requests (Firefox opens 6 concurrent connections) to an Apache instance with
mod_fcgid configured to run fewer than 6 instances of the handling FastCGI
application.  For example if mod_fcgid is configured to run a single instance
of the application (FcgidMaxProcessesPerClass 1) then the first 30 requests are
handled in approximately 150 milliseconds, and the last five take an additional
5 seconds.

The guilty logic in mod_fcgid is located in the handle_request function of
fcgid_bridge.c, where it calls apr_sleep(apr_time_from_sec(1)) if it can't get
an available procnode.

For our application a sleep of 2-5 milliseconds would be much preferable (up to
10 milliseconds would be acceptable in context of our FastCGI application and
related web services).

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