nginx 1.7.9: Reverse Proxy Web Sockets: hangs on service stop / service restart, never exits
Solution 1:
Possibly netstat and tcpdump are useful for debugging as well as lsof - is the worker process still connected and exchanging data? I notice your proxy_read_timeout is a day rather than the default 60s, and wonder if that's significant. It sounds like an nginx bug, and just possibly this post about ZLIB compression and keepalive is related: http://forum.nginx.org/read.php?2,170139,209671