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nginxunicornhaproxycloud66

Dropped connections to server. Haproxy + Nginx + Unicorn

Some requests to my site are failed with "Server unexpectedly dropped the connection" and there is no errors in error logs.

RPM is 1-1.2k.

Do you have any ideas?

Here is configs of haproxy, nginx and unicorn:

https://gist.github.com/releu/59b7f1d649c681856320

Solution

  • Before you share logs which is critical you have misconfiguration:

    1. Nginx worker_connections 3000 Reason: keep it 2-3x more than actual active connections number

    2. Nginx worker_rlimit_nofile 20000. Reason: each single connection requires 2 file descriptors for serving request via proxying

    3. Nginx absence of location that serves static files straight from file system bypass backend. Reason: if you pass any static file via backend it reach the limit very quick

    4. Unicorn worker_processes 4. Reason: 4 workers are not enough to serve 1K RPM

    5. System: I guess there is lack of kernel optimisation. Take a look Unicorn System Kernel tips