# Socket connection failures on 1.6.1~precise **URL:** \ **Category:** NGINX\ **Created:** [September 2, 2014, 6:00pm UTC](https://www.ruby-forum.com/t/socket-connection-failures-on-1-6-1-precise/231845 "2014-09-02T18:00:58Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\ **Post date:** [September 2, 2014, 6:00pm UTC](https://www.ruby-forum.com/t/socket-connection-failures-on-1-6-1-precise/231845/1 "2014-09-02T18:00:58Z")
I’m trying to track down an issue that is being presented only when I run nginx version 1.6.1-1~precise. My nodes running 1.6.0-1~precise do not display this issue, but freshly created servers are getting floods of these socket connection issues a couple times a day. /connect() to unix:/tmp/unicorn.sock failed (11: Resource temporarily unavailable) while connecting to upstream/ The setup I’m working with is nginx proxying requests to a unicorn socket powered by a ruby app. As stated above, the error is NOT present on nodes running 1.6.0-1~precise, but any newly created node gets the newer 1.6.1-1~precise package installed and will inevitably have that error. All settings from nodes running 1.6.0 appear to be the same as newly created nodes on 1.6.1 in terms of sysctl settings, nginx settings, and unicorn settings. All package versions are the same except for nginx. When I downgraded one of the newly created nodes to nginx 1.6.0 using the nginx ppa (ref: [NGINX Stable : “Nginx” team](https://launchpad.net/~nginx/+archive/ubuntu/stable)), the error was not present. Is there any advice, direction, or similar issue experienced that someone else might be able to help me track this down? ---
**Author:** ![Jon\_Clayton](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/73ab20/32.png) [@Jon\_Clayton](https://www.ruby-forum.com/u/Jon_Clayton)\ **Post date:** [September 2, 2014, 9:15pm UTC](https://www.ruby-forum.com/t/socket-connection-failures-on-1-6-1-precise/231845/2 "2014-09-02T21:15:13Z")
Hello! On Tue, Sep 02, 2014 at 11:00:10AM -0500, Jon Clayton wrote: > running 1.6.0-1~precise, but any newly created node gets the newer > Is there any advice, direction, or similar issue experienced that someone > else might be able to help me track this down? Just some information: - In nginx itself, the difference between 1.6.0 and 1.6.1 is fairy minimal. The only change affecting http is one code line added in the 400 Bad Request handling code (see [hg.nginx.org is decommissioned](http://hg.nginx.org/nginx/rev/b8188afb3bbb)). - The message suggests that backend’s backlog is full. This can easily happen on load spikes and/or if a backend is overloaded, and usually unrelated to the nginx itself. – Maxim D. > **[nginx](http://nginx.org/)** ---
**Author:** ![Jon\_Clayton](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/73ab20/32.png) [@Jon\_Clayton](https://www.ruby-forum.com/u/Jon_Clayton)\ **Post date:** [September 2, 2014, 10:36pm UTC](https://www.ruby-forum.com/t/socket-connection-failures-on-1-6-1-precise/231845/3 "2014-09-02T22:36:03Z")
I did see the changelog hadn’t noted many changes and running a diff of the versions shows what you mentioned regarding the 400 bad request handling code. I’m not necessarily stating that nginx is the problem, but it would seem like something had changed enough to cause the backend’s backlog to fill more rapidly. That could be a completely bogus statement as I’ve been attempting to find a way to track down exactly what backlog is being filled, but my test of downgrading nginx back to 1.6.0 from the nginx ppa seemed to also point at a change in nginx causing the issue since the errors did not persist after downgrading. It’s very possible that I’m barking up the wrong tree, but the fact that only changing nginx versions back down to 1.6.0 from 1.6.1 eliminated the errors seems suspicious. I’ll keep digging, but I’m open to any other suggestions. ---
**Author:** ![Jon\_Clayton](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/73ab20/32.png) [@Jon\_Clayton](https://www.ruby-forum.com/u/Jon_Clayton)\ **Post date:** [September 10, 2014, 5:16am UTC](https://www.ruby-forum.com/t/socket-connection-failures-on-1-6-1-precise/231845/4 "2014-09-10T05:16:12Z")
Just closing the loop on this, but what appeared to be happening was that newly created nodes were not having the nginx master PID start up with a custom ulimit set in /etc/security/limits.d/. The workers were all fine since the worker\_rlimit\_nofile was set in the nginx.conf, but I was running into a separate issue that was preventing nginx from inheriting the custom ulimit setting for that master PID file. Truth be told, I never quite nailed down an exact RCA other than ensuring the nginx master PID came up with the custom ulimit setting. That would seem to indicate something was causing a spike in the number of open files for the master PID, but I can look into that separately.