# Proxy returns 504 then blocks next connections **URL:** \ **Category:** NGINX\ **Created:** [July 11, 2013, 9:55pm UTC](https://www.ruby-forum.com/t/proxy-returns-504-then-blocks-next-connections/245739 "2013-07-11T21:55:53Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Rafa\_F](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/958977/32.png) [@Rafa\_F](https://www.ruby-forum.com/u/Rafa_F)\ **Post date:** [July 11, 2013, 9:55pm UTC](https://www.ruby-forum.com/t/proxy-returns-504-then-blocks-next-connections/245739/1 "2013-07-11T21:55:53Z")
I’m having an issue where I proxy a long running script and receive a 504 error when it exceeds my proxy\_read\_timeout setting. All of that’s behaving normally – what isn’t behaving normally is that the next several requests I make to the domain via the same proxy code also return 504s after timing out, despite the fact that the request should complete properly. The first script that runs takes approximately 10 minutes to run and, once it completes on the origin, the server again takes connections. The oddest part is that all of this is specific to the web browser calling the pages on the server. If I access the long running script in Chrome, I can no longer access another page through the proxy until the script finishes on the origin. Meanwhile, I can access pages without issue on Firefox or IE. If I run the script through Firefox, it becomes locked out but Chrome and IE work fine. Here are the relevant proxy lines: proxy\_cache CACHEFOLDER; proxy\_cache\_use\_stale updating error timeout invalid\_header http\_500 http\_502 http\_503 http\_504; proxy\_cache\_valid 60m; proxy\_redirect off; proxy\_connect\_timeout 120; proxy\_send\_timeout 120; proxy\_read\_timeout 120; proxy\_buffers 8 16k; proxy\_buffer\_size 16k; proxy\_busy\_buffers\_size 64k; proxy\_cache\_key $host$request\_uri; proxy\_set\_header X-Forwarded-For $IP; proxy\_set\_header Host $VAR\_HOST; proxy\_pass $REQUEST\_PROTO://$PROXY\_TO; Has anyone experienced anything like this before? Or is there any setting within NGINX that could be the culprit? The server being proxied is running IIS, but when I run the long running script directly against the proxied server, I’m not getting the same behavior. The long running script runs and I’m able to open a new browser tab and continue browsing as well. Posted at Nginx Forum: > **[Proxy returns 504 then blocks next connections](https://forum.nginx.org/read.php?2,240766,240766#msg-240766)** > > I'm having an issue where I proxy a long running script and receive a 504 error when it exceeds my proxy\_read\_timeout setting. All of that's behaving normally -- what isn't behaving normally is that the next several requests I make to the domain via... ---
**Author:** ![abstein2](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/a3d4f5/32.png) [@abstein2](https://www.ruby-forum.com/u/abstein2)\ **Post date:** [July 12, 2013, 2:18am UTC](https://www.ruby-forum.com/t/proxy-returns-504-then-blocks-next-connections/245739/2 "2013-07-12T02:18:40Z")
Does your script use sessions? You didn’t specify with language it uses, but several popular languages such as PHP will lock a session file until the request is complete, preventing multiple requests while the first request continues to run. Mechanisms similar to session\_write\_close() in PHP can work around this, but it sounds like this script should run as a background process rather than as a web request. Posted at Nginx Forum: > **[Re: Proxy returns 504 then blocks next connections](https://forum.nginx.org/read.php?2,240766,240771#msg-240771)** > > I'm having an issue where I proxy a long running script and receive a 504 error when it exceeds my proxy\_read\_timeout setting. All of that's behaving normally -- what isn't behaving normally is that the next several requests I make to the domain via... ---
**Author:** ![abstein2](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/a3d4f5/32.png) [@abstein2](https://www.ruby-forum.com/u/abstein2)\ **Post date:** [July 15, 2013, 6:47am UTC](https://www.ruby-forum.com/t/proxy-returns-504-then-blocks-next-connections/245739/3 "2013-07-15T06:47:11Z")
The script is an ASPX script and, to my knowledge, it doesn’t use sessions. I don’t control the script, but I can’t duplicate the behavior when running against the proxied server. It only occurs when going through the proxy. I don’t believe sessions are the issue. Posted at Nginx Forum: > **[Re: Proxy returns 504 then blocks next connections](https://forum.nginx.org/read.php?2,240766,240842#msg-240842)** > > I'm having an issue where I proxy a long running script and receive a 504 error when it exceeds my proxy\_read\_timeout setting. All of that's behaving normally -- what isn't behaving normally is that the next several requests I make to the domain via... ---
**Author:** ![abstein2](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/a3d4f5/32.png) [@abstein2](https://www.ruby-forum.com/u/abstein2)\ **Post date:** [July 15, 2013, 1:05pm UTC](https://www.ruby-forum.com/t/proxy-returns-504-then-blocks-next-connections/245739/4 "2013-07-15T13:05:52Z")
Hello! On Mon, Jul 15, 2013 at 12:46:41AM -0400, abstein2 wrote: > The script is an ASPX script and, to my knowledge, it doesn’t use sessions. > I don’t control the script, but I can’t duplicate the behavior when running > against the proxied server. It only occurs when going through the proxy. I > don’t believe sessions are the issue. For me it looks like the problem is a concurent connections limit in a browser. Not sure why it’s triggered though, but probably there are other connections to the same host open. If you are using Chrome, try looking into chrome://net-internals/ page, it might be helpful. – Maxim D. > **[nginx: donation](http://nginx.org/en/donation.html)**