upstream prematurely closed connection while reading response header from upstream

Question

I am having issues setting up SSL for my Jenkins CI server. I use Jenkins behind nginx for a reverse proxy. I am getting these upstream prematurely closed connection while reading response header from upstream errors in my jenkins.error.log file.

2014/09/30 13:01:49 [error] 4875#0: *1 upstream prematurely closed connection while reading response header from upstream, client: <MY IP ADDR>, server: jenkins.<SERVER URL>.com, request: "GET /favicon.ico HTTP/1.1", upstream: "http://127.0.0.1:8080/favicon.ico", host: "jenkins.<SERVER URL>.com"
2014/09/30 13:01:50 [error] 4875#0: *1 upstream prematurely closed connection while reading response header from upstream, client: <MY IP ADDR>, server: jenkins.<SERVER URL>.com, request: "GET / HTTP/1.1", upstream: "http://127.0.0.1:8080/", host: "jenkins.<SERVER URL>.com"

Jenkins is up and running. I am able to connect via https://<SERVER IP ADDR>:8080 (even though Chrome complains about the certificate). nginx gives me a 502 Bad Gateway message for the official url though.

sites-available configuration:

upstream jenkins {
    server 127.0.0.1:8080 fail_timeout=0;
}

server {
  listen 80;
  return 301 https://$host$request_uri;
}

server {
  listen 443;
  #listen [::]:443 default ipv6only=on;
  server_name jenkins.<SERVER URL>.com <SERVER IP ADDR>;

  ssl on;
  ssl_certificate /etc/nginx/ssl/jenkins.<SERVER URL>.com.chained.crt;
  ssl_certificate_key /etc/nginx/ssl/<SERVER URL>.com.key;

  access_log /etc/nginx/logs/jenkins.access.log;
  error_log /etc/nginx/logs/jenkins.error.log;

  location / {
    proxy_set_header        Host $host;
    proxy_set_header        X-Real-IP $remote_addr;
    proxy_set_header        X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header        X-Forwarded-Proto $scheme;
    proxy_redirect          http:// https://;
    proxy_pass              http://jenkins;
  }
}

Answer 1

The issue was with Jenkins itself. We originally disabled the http port for Jenkins and only allowed https. Once we allowed http again, we only allowed requests from 127.0.0.1 and that solved our issues.

tl;dr: enable http port, only allow requests through 127.0.0.1