Encourage leak containment by limiting the number of requests a CKAN process serves

[nils.toedtmann]

CKAN has memory leaks. They can be contained by limiting the time-to-live of a ckan process. An easy way to achieve this is to limit the number of requests a ckan server process can serve before it gets killed and replaced.

One should ...

• research ways to limit requests-per-process with the different web servers (see below for a start);
• explain these safeguards in the CKAN documentation and encourage users to apply them;
• consider the helper script ​ckan-create-instance to generate Apache configs with WSGIDaemonProcess ... maximum-requests=XY being active instead of ​commented out. Or at least let it warn the user to use MaxRequestsPerChild;
• Investigate current CKAN deployments whether they suffer from mem leaks, and if so contain them.

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How to limit requests-per-process

• Apache:
  • Use WSGIDaemonProcess with maximum-requests=50 or whatever limit is appropriate. We did this sucessfully on ​datahub.io and the ​ckan farm
  • (This need to be verified) Without WSGIDaemonProcess, MaxRequestsPerChild 50 should achieve the same.
• nginx/supervisord: to be researched.