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POMysterious ~1min delay in HTTP POST between browser and Nginx
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12606898
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2012-09-26T17:07:18.177
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2012-09-26T17:19:29.163
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We've lately been experiencing a very strange but very consistent delay when POSTing from client-side javascript to our server. Here's our technology stack, from front to back: <ol> <li>Custom javascript client code</li> <li>Backbone.js</li> <li><a href="https://gist.github.com/3789008">Custom Backbone.sync() implementation</a></li> <li>jQuery.ajax() (1.7.2)</li> <li>XmlHttpRequest</li> <li>Browser (verified on both Firefox and Chrome)</li> <li>Internet</li> <li>Nginx front-end</li> <li>Intranet (via Nginx <code>http://</code> upstream)</li> <li>Nginx back-end</li> <li>Gunicorn (via Nginx <code>unix://</code> upstream socket)</li> <li>Django 1.4</li> <li>django-tastypie</li> </ol> (Side note: do you ever just step back in awe at how complicated web development is?) Here's a timeline of events: <ol> <li>Client code calls <code>.save()</code> on a newly created Backbone <a href="https://gist.github.com/3789008#L358"><code>APIModel</code></a>.</li> <li>Our custom <a href="https://gist.github.com/3789008#L245"><code>.sync()</code></a> winds its way to <a href="https://gist.github.com/3789008#L180"><code>client.send()</code></a> which dispatches the newly created object to <a href="http://api.jquery.com/jQuery.ajax/"><code>$.ajax()</code></a>.</li> <li>The resulting XmlHttpRequest POSTs. The request appears in the browser dev tool's Network pane, marked as pending.</li> <li>The HTTP request reaches Nginx, which routes it to the django-tastypie backend.</li> <li>Tastypie handles the request promptly and flawlessly, creating the resource, and returning a 201 CREATED response, with a <code>Location</code> header pointing to the new resource.</li> <li>Nginx logs the request and (ostensibly) sends the response.</li> <li>1.1 minutes elapse, during which the request is still marked as pending in the Network pane.</li> <li>The request is marked as complete in the browser's Network pane.</li> <li>The jQuery <code>xhr</code> fires success handlers</li> <li>Our custom API client's <a href="https://gist.github.com/3789008#L223">success handler</a> detects the 201 response code and fires off a subsequent GET request to the Location.</li> <li>The usual stuff happens, the GET responds promptly, and the outermost <code>$.Deferred()</code> object resolves, firing any associated client code success handlers.</li> </ol> Other details to consider: <ol> <li>GET requests and PUT requests in the same stack resolve promptly.</li> <li>When interacting directly with the outermost Nginx via a dedicated HTTP client, POST requests identical to the request in question resolve promptly.</li> <li>Removing the special-case 201 handler and subsequent GET has no effect on the bug.</li> <li>The delay is always 1.1 minutes. I've used <code>console.time()</code> to determine that the delay varies within the 65,000ms range.</li> <li>The delay only appears in this configuration. It does not occur in our development setups, which are slightly simpler.</li> </ol> Unverified assumptions I'm making: <ol> <li>Once Nginx logs a request, the response has been tied up with a bow and sent to the client with a handwritten thank-you note.</li> <li>This is not a bug in the browsers or in jQuery.</li> </ol> Forgive the painstaking detail, but I've done my best to eliminate variables, and at present, I feel safe in saying that the problem is one of the following: <ol> <li>a flaw in the physical structure of the universe</li> <li>a flaw in the perceptual models of our minds</li> <li>something else we haven't considered yet</li> </ol> I'm hoping for #3. Any ideas?
Tags
<javascript><backbone.js><nginx><xmlhttprequest><tastypie>
Title
Mysterious ~1min delay in HTTP POST between browser and Nginx
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1. USDavid Eyk
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