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POxmlhttprequest timeout / abort not working as expected?
 

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    <p>Here is my AJAX function:</p> <pre><code>/** * Send an AJAX request * * @param url The URL to call (located in the /ajax/ directory) * @param data The data to send (will be serialised with JSON) * @param callback The function to call with the response text * @param silent If true, doesn't show errors to the user * @param loader The element containing "Loading... Please wait" */ AJAX = function(url,data,callback,silent,loader) { var a, attempt = 0, rsc = function() { if( a.readyState == 4) { if( a.status != 200) { if( a.status &gt; 999) { // IE sometimes throws 12152 attempt++; if( attempt &lt; 5) send(); else if( !silent) { alert("HTTP Error "+a.status+" "+a.statusText+"&lt;br /&gt;Failed to access "+url); } } else if(!silent) { alert("HTTP Error "+a.status+" "+a.statusText+"\nFailed to access "+url); } } else { callback(JSON.parse(a.responseText)); } } }, to = function() { a.abort(); attempt++; if( attempt &lt; 5) send(); else if( !silent) { alert("Request Timeout\nFailed to access "+url); } }; data = JSON.stringify(data); var send = function() { if( loader &amp;&amp; attempt != 0) { loader.children[0].firstChild.nodeValue = "Error... retrying..."; loader.children[1].firstChild.nodeValue = "Attempt "+(attempt+1)+" of 5"; } a = new XMLHttpRequest(); a.open("POST","/ajax/"+url,true); a.onreadystatechange = rsc; a.timeout = 5000; a.ontimeout = to; a.setRequestHeader("Content-Type","application/json"); a.send(data); }; send(); }; </code></pre> <p>The general idea is to attempt the request up to five times. Sometimes IE fails with an unusual HTTP error (12xxx), and sometimes the server may fail to respond.</p> <p>The problem I'm having is that the <code>abort()</code> call doesn't appear to be aborting the connection. To test, I made a simple PHP script:</p> <pre><code>&lt;?php sleep(60); touch("test/".uniqid()); die("Request completed."); ?&gt; </code></pre> <p>The <code>touch()</code> call creates a file with the current <code>uniqid()</code> - by looking at the modification time I can see the time the <code>sleep(60)</code> ended.</p> <p>Expected behaviour:</p> <blockquote> <p>The request is sent<br> After five seconds, the text changes to "Error... Retying... Attempt 2/5"<br> Repeat the above up until Attempt 5/5, then fail.<br> The five calls to the PHP file are aborted, and either there will be five files in the "test" folder, spaced 5 seconds apart, or there will be none because ignore_user_abort is off.</p> </blockquote> <p>Observed behaviour (in IE9):</p> <blockquote> <p>The request is sent<br> The attempt text appears and changes as it should<br> After five attempts, the error message is displayed<br> I am unable to load any pages for five whole minutes.<br> On the server, there are five files spaced one minute apart</p> </blockquote> <p>I don't know what to make of this, because on the server side Requests 3, 4 and 5 are being sent minutes after the "Timeout" error message is shown on the browser.</p> <p>If it makes any difference, the page making the AJAX calls is in an iframe. Reloading the iframe (using <code>iframe.contentWindow.location.reload()</code> does NOT fix the issue, it still waits for those five requests to go through.</p> <p>Why is this happening? How can I fix it?</p> <p><strong>EDIT:</strong> I've run the test again using Developer Tools to monitor network activity. The result is:</p> <pre><code>URL Method Result Type Received Taken Initiator /ajax/testto (Aborted) 0 B &lt; 1 ms (Pending...) /ajax/testto (Aborted) 0 B 125 ms (Pending...) /ajax/testto (Aborted) 0 B 125 ms (Pending...) /ajax/testto (Aborted) 0 B 125 ms (Pending...) /ajax/testto (Aborted) 0 B 124 ms (Pending...) </code></pre>
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