Session Locking. Some people don’t ever consider this. I have dealt with it before in another language, so I decided to do a quick search to see what it looks like in PHP.
The basic idea is that only one process can have a file open for writing at a time. Session information is kept in files, and since you can have multiple hits coming into your web page simultaneously, things have to be processed in order, in a queue. This can cause your site to slow down under heavy load.
There are techniques you can use to help speed things up.
What I found is this:
<?php // start the session session_start(); // I can read/write to session $_SESSION['latestRequestTime'] = time(); // close the session session_write_close(); // now do my long-running code. // still able to read from session, but not write $twitterId = $_SESSION['twitterId']; // dang Twitter can be slow, good thing my other Ajax calls // aren't waiting for this to complete $twitterFeed = fetchTwitterFeed($twitterId); echo json_encode($twitterFeed); ?>
For an explanation of what’s going on here, check out the original post at http://konrness.com/php5/how-to-prevent-blocking-php-requests/