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Asked: 2026-06-05T07:26:41+00:00

I have this strange issue where sometimes if I make two AJAX requests to

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I have this strange issue where sometimes if I make two AJAX requests to my Apache 2.2 server in rapid succession, the second request will wait for the first to finish before finishing.

Example, I have two requests, one that sleeps for 10 seconds and one that returns immediately. If I run the request that returns immediatly by itself it will always return within 300ms. However, if I call the request that takes 10 seconds, and then call the request that returns right away about 50% of the time the second request will wait until the first finishes and chrome will report that the request too about 10 seconds before receiving a response. The other half of the time the quick request will return right away.

I can’t find any pattern to make it behave one way or another, it will just randomly block the quick AJAX requests sometimes, and other times it will behave as expected. I’m working on a dev server that only I am accessing and I’ve set several variables such as MaxRequestsPerChild to a high value.

Does anyone have any idea why Apache, seemingly at random, is turning my AJAX requests into synchronous requests?

Here is the code I’m running:

$.ajax({async:true,dataType:'json',url:'/progressTest',success:function(d){console.log('FINAL',d)}}); // Sleeps for 10 seconds
$.ajax({async:true,dataType:'json',url:'/progressTestStatus',success:function(d){console.log('STATUS',d)}}); // Takes ~300ms

And here are two screen shots. The first where it behaved as expected and the second where it waited for the slow process to finish first (in the example the timeout was set to 3 seconds).

Expected async behavior

Async behavior

UPDATE: Per the comments below – this appears to be related to Chrome only performing one request at a time. Any ideas why Chrome would set such a low limit on async requests?

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1 Answer

  1. Editorial Team

    The problem is not with Apache but with Google Chrome limiting the number of concurrent requests to your development server. I can only make guesses as to why it’s limited to one request. Here are a couple:

    1) Do you have many tabs open? There is a limit to the total number of concurrent connections and if you have many tabs making requests with KeepAlive you may be at that limit and can only establish one connect to your server. If that’s the case you might be able to fix that by adding KeepAlive to your own output headers.

    2) Do you have some extensions enabled. Some extensions do weird things to the browser. Try disabling all your extensions and making the same requests. If it works then enable them one at a time to find the culprit extension.

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