Apache ReverseProxy 502 to local jenkins process

Question

I have apache listening on port 443 running https and performing a ProxyPass back to a standalone jenkins process on the same server.

The bulk of the time, this works fine, but it often produces a 502 error. I can reproduce this by loading the jenkin's web page up and having it auto refresh. Often within 20 minutes of doing so, I can get a 502 page.

I enabled debug logging in Apache and provided my config + apache logs below. Jenkins logs reveal nothing (like it never received the request).

I need some more pointers on tracking this down (and ultimately resolve).

Apache/2.2.3 Jenkins ver. 1.451

 <Location /> ProxyPass http://jenkins.example.com:8080/ ProxyPassReverse http://jenkins.example.com:8080/ </Location> /usr/lib/jvm/jre-1.6.0/bin/java -Dcom.sun.akuma.Daemon=daemonized -Djava.awt.headless=true -DJENKINS_HOME=/var/lib/jenkins -jar /usr/lib/jenkins/jenkins.war --logfile=/var/log/jenkins/jenkins.log --daemon --httpPort=8080 --ajp13Port=8009 --debug=5 --handlerCountMax=100 --handlerCountMaxIdle=20 

Myself getting the error: 192.168.186.207 - - [13/Mar/2013:09:23:16 -0400] "GET /?auto_refresh=true HTTP/1.1" 502 473

[Wed Mar 13 09:23:16 2013] [info] Initial (No.1) HTTPS request received for child 10 (server jenkins.example.com:443) [Wed Mar 13 09:23:16 2013] [debug] mod_proxy_http.c(56): proxy: HTTP: canonicalising URL //jenkins.example.com:8080/ [Wed Mar 13 09:23:16 2013] [debug] proxy_util.c(1505): [client 192.168.186.207] proxy: http: found worker http://jenkins.example.com:8080/ for http://jenkins.example.com:8080/?auto_re fresh=true, referer: https://jenkins.example.com/?auto_refresh=true [Wed Mar 13 09:23:16 2013] [debug] mod_proxy.c(986): Running scheme http handler (attempt 0) [Wed Mar 13 09:23:16 2013] [debug] mod_proxy_http.c(1982): proxy: HTTP: serving URL http://jenkins.example.com:8080/?auto_refresh=true [Wed Mar 13 09:23:16 2013] [debug] proxy_util.c(2007): proxy: HTTP: has acquired connection for (jenkins.example.com) [Wed Mar 13 09:23:16 2013] [debug] proxy_util.c(2063): proxy: connecting http://jenkins.example.com:8080/?auto_refresh=true to jenkins.example.com:8080 [Wed Mar 13 09:23:16 2013] [debug] proxy_util.c(2189): proxy: connected /?auto_refresh=true to jenkins.example.com:8080 [Wed Mar 13 09:23:16 2013] [error] [client 192.168.186.207] (104)Connection reset by peer: proxy: error reading status line from remote server jenkins.example.com, referer: https://jenkins.example.com/?auto_refresh=true [Wed Mar 13 09:23:16 2013] [debug] mod_proxy_http.c(1484): [client 192.168.186.207] proxy: NOT Closing connection to client although reading from backend server jenkins.example.com failed., r eferer: https://jenkins.example.com/?auto_refresh=true [Wed Mar 13 09:23:16 2013] [error] [client 192.168.186.207] proxy: Error reading from remote server returned by /, referer: https://jenkins.example.com/?auto_refresh=true [Wed Mar 13 09:23:16 2013] [debug] proxy_util.c(2025): proxy: HTTP: has released connection for (jenkins.example.com) [Wed Mar 13 09:23:16 2013] [debug] ssl_engine_kernel.c(1823): OpenSSL: Write: SSL negotiation finished successfully [Wed Mar 13 09:23:16 2013] [info] [client 192.168.186.207] Connection closed to child 10 with standard shutdown (server jenkins.example.com:443) [Wed Mar 13 09:23:17 2013] [info] [client 192.168.186.207] Connection to child 7 established (server jenkins.example.com:443) 

Answer 1

"502" means that there is a problem with the backend server, not with Apache. You can also see this in the log:

[Wed Mar 13 09:23:16 2013] [error] [client 192.168.186.207] (104)Connection reset by peer: proxy: error reading status line from remote server jenkins.example.com, referer: https://jenkins.example.com/?auto_refresh=true 

It's your Jenkins Server that is hanging up on the apache server. Try if the problem also appears if you do this directly on your Jenkins instance (port 8080).