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PO502 Bad Gateway on WSGI app using Nginx + Cherrypy
 

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    <p>I have a Python application served via CherryPy's WSGI server, receiving requests from Nginx. It's hosted on a Windows Server 2003 box, and there are only a few users accessing it.</p> <p>Sometimes, requests to a specific resource fail almost instantly with a <strong>502 Bad Gateway</strong> on Firefox. I've tried to reproduce the problem on other browsers, without success.</p> <p>The application is started like this:</p> <pre><code>paths = { "/resource": resource_func } dispatcher = wsgiserver.WSGIPathInfoDispatcher(paths) server = wsgiserver.CherryPyWSGIServer(("127.0.0.1", 9191), dispatcher) server.start() </code></pre> <p>The nginx server is forwarding requests to CherryPy via <code>proxy_pass</code>:</p> <pre><code>location / { proxy_pass http://127.0.0.1:9191/; proxy_redirect off; proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; } </code></pre> <p>The requests are sent via jQuery.ajax method:</p> <pre><code>$.ajax(requestURI).done(myRequestCallback); </code></pre> <p>If I run Firebug, then open nginx error log when a 502 occurs, I see the following error:</p> <pre><code>(time): *92 WSASend() failed (10054: An existing connection was forcibly closed by the remote host) while sending request to upstream, client: xxx.xxx.xxx.xxx, server: localhost, request: "GET /resource?params=VALUES&amp;_=1371674388573 HTTP/1.1", upstream: "http://127.0.0.1:9191/resource?params=VALUES&amp;_=1371674388573", host: "xxx.xxx.xxx.xxx:9080", referrer: "http://172.27.129.112:9080/myAppPage.html" </code></pre> <p>... where <code>xxx.xxx.xxx.xxx</code> is the IP from which I'm testing the application, and nginx is listening to <code>9080</code>.</p> <p>The failing requests do not show up in our app's log file, and the same resource and params are valid (a request does not fail on every attempt).</p> <p>I've even added the following lines to my nginx.conf file (then restarted both servers) to try to fix the problem, but it didn't seem to make ay difference:</p> <pre><code>proxy_buffers 8 16k; proxy_buffer_size 32k; </code></pre> <p>The versions are:</p> <ul> <li>Firefox 21</li> <li>Python 2.7.5</li> <li>nginx 1.2.0</li> <li>CherryPy 3.2.2</li> </ul> <p>What could be causing the error?</p>
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