The return of Service Unavailable HTTP Error 503

For those of you that have read my first article in this blog, one of the reasons for the migration to a new server was because I was plagued with Service Unavailable HTTP Error 503, which would forever get under my skin and just 'error' for no real reason at all.  Nothing in the error logs, no software errors, nothing.  I was aware of the IMAP PHP module being faulty, whereby if the headers of an email were over a certain length, this would result in the 'Error 503'.  I could replicate this just fine, but the server would still fall over for no reason, even if I disabled the IMAP module.

This started on Server 2003r2 with IIS6.  Some time ago, after Googling around for a little while, I eventually found that other people experiencing the same issues with some people were saying this was down to a corrupt IIS configuration.  I had never experienced this before so it eventually started to turn into a bit of a headache trying to pin this down.  It had been on the cards for some time to move the server to a new box so for me to waste time reinstalling IIS was pointless.

Moving forward a year or so, and the problem had gradually been getting more frequent.  In the end, I just made a small VB Script as a workaround that would run every few hours to restart IIS in case this had happened which always cured the problem.  This had worked fine and my hope was that a planned server upgrade would solve this issue along with an updated version of PHP.  Wrong.  A few days into the new server being in production, what happens?  Yep, you got it.  Error 503.  Great.

Only this time there was a log entry in the Windows application log.  The shortened error looked like:

Faulting application name: w3wp.exe, Faulting module name: php_imap.dll

Google again came to the rescue, with the top result pointing at this PHP bug article about IMAP headers being too long - the same bug that was present before.  It looks as though the old problem had not been cured and it seemed that the only way to fix this would be to go up a major point release of PHP to PHP 5.3.5 (current release as of now).  ISAPI was always my favourite method for PHP use on Windows, but since this has now been retired as of the last branch of 5.2, FastCGI was now my only option.

FastCGI wasn't a problem though and it does work just as well as ISAPI although it does require a bit more of a tweak to get it set up out of the box.  So far so good though.  No more 503s.  I do think that originally the 503s were the result of the faulty IMAP module, but there still must have been a massive fault with IIS6 which is now now present in 7.5.

I would just like to say thanks to everybody who has been clicking on the sponsored adverts on this page.  It's very much appreciated.