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Hi Folks,</div>
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I've inherited an nginx plugin, written against 0.7.69 that has recently been moved to use nginx 1.24.0 to resolve the need to ship old versions of openssl. </div>
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I've found during performance testing that it's leaking file descriptors. After a few hours running and leaking I hit my configured limit of 100k worker_connections which gets written to logs, and nginx starts "reusing connections".</div>
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The leaked file descriptors don't show up in the output of "ss", they look like this in lsof:</div>
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$ /usr/bin/lsof -p 2875952 | grep protocol | head -2</div>
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nginx 2875952 user 8u sock 0,8 0t0 2222824178 protocol: TCP</div>
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nginx 2875952 user 19u sock 0,8 0t0 2266802646 protocol: TCP</div>
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Googling suggests this may be a socket that has been created but never had a "bind" or "connect" call. I've combed through our plugin code, and am confident it's not responsible for making and leaking these sockets. </div>
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I should flag two stinkers which may be responsible:</div>
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We have "lingering_timeout" set to an hour, a hack to allow long poll / COMET requests to not be torn down before responding. Stopping load and waiting for an hour does drop some of these leaked fds, but not all. After leaking 17k fds, I stopped my load test
and saw it drop to 7k fds which appeared to remain indefinitely. Is this a terrible idea? </div>
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Within our plugin, we are incrementing the request count field for the same purpose. I'm not really sure why we need both of these, maybe I'm missing something but I can't get COMET polls to work without. I believe that was inspired by Nchan which does something
similar. Should I be able to avoid requests getting torn down via this method without lingering_timeout? </div>
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What could be responsible for these leaked file descriptors and worker connections? I'm unexperienced with nginx so any pointers of where to look are greatly appreciated. </div>
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Many thanks,</div>
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Alex</div>
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