php suddenly very very very slow

Question

I'm working on a webapp using php, apache en mysql. For the past year the response times of this application have been good. Suddenly yesterday the application became very slow on firefox (complete page load, including css and js files: around 20 secs. During page load firefox is completely unusable). Interestingly the responsetimes in IE were a bit slower (around 2 secs instead of <1 sec).

The strange thing is: The application worked fine two days ago and out of nowhere became very slow. I didn't change anything in the sourcecode. I didn't change a thing in php.ini or httpd.conf. I already log the response times of php functions and that performance hasn't changed.

At first I thought it had something to do with firefox, so I completely removed firefox, restarted vista and did a clean install of firefox (without extensions). No result.

After testing several things I found out that when I copy the application data to another folder in my document root, the application works fine again. Problem solved you could think but it's very annoying that I now have to use another URL and (more important) I don't get it. Why is my application very very very slow in one folder and perfectly fine in another folder? Does it have something to do with firefox or with apache? The name of the folder in which the application is very slow does not appear in either php.ini or httpd.conf. Suggestions anyone?

Answer 1

Do you have any folder/subfolder with an insane amount of small / temp files?

Answer 2

Look for areas that might cause blocking, like shelling out to curl or opening a file over NFS in the code. If the remove system is timing out, it will drastically affect apache performance as each request ties up the server for however many seconds it takes to time out and fail the lagging request.

Answer 3

Some suggestions:

1. Install Fiddler on the client. This will allow you to analyse the low-level HTTP traffic coming from the server.

2. Extract some of the queries from your PHP code and run them interactively in the MySQL client and see if they're running slowly.

3. Log into the server (or get a sysadmin if you don't have access) and run the Task Manager (Windows) or top (Unix) and make sure there's nothing else hogging the server. If you haven't changed anything, maybe something else has changed on the server. Also, check the server logs/ Event Viewer.

4. There is a Zend extension called APD that you can install on the server (again, assuming you have rights) and it will profile your PHP code and write out a file showing what functions are being called by your PHP scripts are how long PHP is spending in each function.

Answer 4

this sounds like a javascript issue to me, a PHP request would not make firefox unusable where as an errant javascript script could very easily do this. Does the error persist if you disable javascript?

Answer 5

Did you change any network settings in your development setup recently? If so, you might encounter one of Mozillas IPv6 bugs. See this blog entry (taken from this question & answers) for details, and this mozillaZine article for more details and a quick option to test it.