Disclaimer: To my regular readers (if there are any) this post is entirely technical in nature so if you’re not looking for the solution to this particular problem (e.g. from Google) you’re probably not interested in this post.

I run a few sites that use PHP as a reverse proxy for other sites. The PHP script loads a specific webpage, then sub-requests for resources like stylesheets, images, and javascripts, are also processed by the same PHP script. For most of these other resources the script simply passes the content through unchanged.

Problem:

When a page is loaded that includes a large amount of supporting resources like CSS and javascript files, it seems to take a long time to load some of the CSS and javascript files. Some of the scripts were taking upwards of 15 seconds to load when loaded as part of the page (although if loaded on their own through the PHP script, they load instantly).

Short Term Solution

The investigation of the problem determined that the problem lies in the KeepAlive setting in Apache. Turning Keep Alive off fixes the issue and yields excellent load times consistently for all resources. But WHY??

Long Term Solution

Keep Alive is generally a good thing and it is supposed to boost performance. So why is it a bad thing in this context? (I really don’t know the answer yet). I would like to find a PHP solution to this problem that will work with KeepAlive, but I can only speculate at this point as to why this might be happening.

Possible reasons that I’ve considered:

1. I need to do something more than “exit” at the end of the PHP script to declare that I’m done with the request – as Apache could be keeping the connection open for longer than necessary and preventing subsequent requests from happening.
2. Perhaps there is some setting that I am unaware of in PHP that limits the number of simultaneous requests it can handle from the same client… (I find this unlikely – at least at the level that we’re talking about here).

Edit:

I found that simply adding the ‘Connection:close’ header in the PHP script resolves this issue.
But i’m still not satisfied. This shouldn’t be necessary IMHO. If you set the Connection-Length properly then flush that content to the browser, there’s no reason why PHP should be making the browser wait around indefinitely.

So maybe we’re missing a few performance points here – but at least it’s not hanging like it was.