Nginx + Rails + Unicorn如何避免502 Bad Gateway？

Question

I have same 502 errors everyday, but can't find reason of that.

2014/12/22 16:33:03 [error] 1697#0: *331 upstream prematurely closed connection while reading response header from upstream, client: 105.121.243.92, server: server01.domain.com, request: "GET /doco/in_documents HTTP/1.0", upstream: "http://unix:/tmp/unicorn.docs.sock:/doco/in_documents", host: "go.domain.com:443"
2014/12/22 16:33:05 [error] 1697#0: *331 connect() failed (111: Connection refused) while connecting to upstream, client: 105.121.243.92, server: server01.domain.com, request: "GET /doco/in_documents HTTP/1.0", upstream: "http://10.213.0.46:80/doco/in_documents", host: "go.domain.com:443"
2014/12/22 16:33:09 [error] 1697#0: *334 upstream prematurely closed connection while reading response header from upstream, client: 10.212.255.3, server: server01.domain.com, request: "GET /doco/in_documents HTTP/1.1", upstream: "http://unix:/tmp/unicorn.docs.sock:/doco/in_documents", host: "server01.domain.com"
2014/12/22 16:33:09 [error] 1697#0: *334 connect() failed (111: Connection refused) while connecting to upstream, client: 10.212.255.3, server: server01.domain.com, request: "GET /doco/in_documents HTTP/1.1", upstream: "http://10.213.0.46:80/doco/in_documents", host: "server01.domain.com"
2014/12/22 16:33:15 [info] 1697#0: *333 client closed connection while waiting for request, client: 10.212.255.3, server: 0.0.0.0:80
2014/12/22 16:33:15 [info] 1697#0: *335 client closed connection while waiting for request, client: 10.212.255.3, server: 0.0.0.0:80
2014/12/22 16:33:15 [info] 1697#0: *336 client closed connection while waiting for request, client: 10.212.255.3, server: 0.0.0.0:80
2014/12/22 16:33:15 [info] 1697#0: *338 client closed connection while waiting for request, client: 10.212.255.3, server: 0.0.0.0:80
2014/12/22 16:33:15 [info] 1697#0: *337 client closed connection while waiting for request, client: 10.212.255.3, server: 0.0.0.0:80
2014/12/22 16:33:17 [info] 1697#0: *334 epoll_wait() reported that client prematurely closed connection, so upstream connection is closed too while sending request to upstream, client: 10.212.255.3, server: server01.domain.com, request: "GET /doco/in_documents HTTP/1.1", upstream: "http://unix:/tmp/unicorn.docs.sock:/doco/in_documents", host: "server01.domain.com"
2014/12/22 16:33:19 [info] 1698#0: *343 epoll_wait() reported that client prematurely closed connection, so upstream connection is closed too while sending request to upstream, client: 105.121.243.92, server: server01.domain.com, request: "GET /doco/in_documents HTTP/1.0", upstream: "http://unix:/tmp/unicorn.docs.sock:/doco/in_documents", host: "go.domain.com:443"
2014/12/22 16:33:35 [info] 1698#0: *347 client closed connection while waiting for request, client: 10.212.255.3, server: 0.0.0.0:80
2014/12/22 16:33:35 [info] 1698#0: *346 client closed connection while waiting for request, client: 10.212.255.3, server: 0.0.0.0:80

Any ideas how to avoid this? I tried different ways from another questions but it has no effect.

Answer 1

According to your error log and the returned status(502), one thing is sure that your upstream server didn't give back a response. I suggest you check your upstream configuration, the address, the port, or something else.