Is there a way to specify a condition in apache httpd access_log to persist only requests which took longer than 500ms to process?

  • I'm confused. Are you trying to just create a log of slow requests or are you trying to make the server hang on to the connection if it takes a long time to process? If the latter, then you may want to look up the network term KeepAlive – Mike Jul 22 '17 at 15:39
  • I want to get a list of HTTP requests which tool longer than expected. I need it in order to create a plan of website optimization. – Antonio Jul 22 '17 at 17:06

The CustomLog directive allows you to set a condition (in an optional 3rd argument) that is used to control when the request is logged. (On Apache 2.4+ this can take the form of an Apache Expression.) However, this condition is generally based on a property of the request (file type, request header, etc.), rather than something that is associated with the response. (Although it does seem possible to create a condition based on the HTTP response status, as this is explicitly made available in the REQUEST_STATUS server variable.)

However, I don't see a way to create a conditon based on the server response time. (?)

A workaround might be to specifically include this information in your access log using the format string %msT (if you specifically want this logged as milliseconds) in a custom log format. You can then filter this information using a log file analyzer.

  • %T - The time taken to serve the request, in seconds.

  • %{UNIT}T - The time taken to serve the request, in a time unit given by UNIT. Valid units are ms for milliseconds, us for microseconds, and s for seconds. Using s gives the same result as %T without any format; using us gives the same result as %D. Combining %T with a unit is available in 2.4.13 and later.

Reference:
http://httpd.apache.org/docs/current/mod/mod_log_config.html#formats

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