Server locking up after 25+ AJAX requests

...surely my server can handle more than 25 requests at a time!

[rollinj]

I'm calling 100+ AJAX GET requests to a dynamic PHP file on my own server. The request goes something like this:

- user submits list of info via HTML form
- PHP crafts user's list into individual AJAX requests, which work away trying to find results, adding any information received to an HTML table.

So basically I'm just calling a list of AJAX GET requests like so:
phpPage.php?arbitrary=user_info_1
phpPage.php?arbitrary=user_info_2
phpPage.php?arbitrary=user_info_3

The problem is, my server keeps locking up with more than ~25 items in the list...!

Each AJAX request involves either a CURL or mysql call and should not take longer than a minute or two, you don't even notice an increase in CPU use with the 25 or so requests I can handle.

If all called at once, the entire page should not take longer than a few minutes to load, but it's proving to take 20-30 minutes.

If I try to access any other page on my server from the same firefox window, it wont load until all the AJAX requests from the original page have finished.

HOWEVER, you can access the server and the related PHP pages through IE

Additional information:
- the phpPage.php is using CURL to access certain items if not already found in the MySQL cache, could this limitation be inside CURL?
- I am running XAMPP on my home windows xp professional computer, but have not had any load problems with it in the past, she's pretty sturdy!
- I'm willing to post or message you the full javascript source code if you think it might help!

[incrediBILL]

For starters I can tell you making 20-30 concurrent CURL connections isn't that fast to start with as each CURL connection has to mitigate DNS, connect to the server, yada, yada.

Have you tried watching server side to see if it's causing a serious task backlog?

[Fotiman]

Based on HTTP spec recommendations, browsers limit the number of connections to a server. This was meant to prevent a single browser from hogging all of the connections to the server (which was a larger issue before broadband became more popular).

IE8 is limited to 6 concurrent connections. Earlier versions of IE had a limit of 2. You can change that by editing the registry.
[support.microsoft.com...]

Firefox also has a limit, and there are several settings that might be related to your issue. From the sound of it, you're reaching the network.http.max-connections [kb.mozillazine.org] limit, which has a default value of 24. It is possible to change your configuration settings [developer.mozilla.org] to allow for more connections, but this will only affect your own instance of Firefox, so if you have other users that need to access this, then they will still see the delay (unless they too have modified their settings). Hope this helps.