Intermittent blank page/cache issue

[pat11]

Hi,

I'm having an intermittent problem with my client's site - every now and then it refuses to load content and just shows a blank page.  Refreshing over and over again does not seem to fix it.  The admin section will work fine, and the way my client gets it working again is to go into the main template and save it again without changing anything.

I have only had one chance to get access to it whilst it's been down, I immediately went in and turned on debug mode in config.php and the site loaded straight away (with all the debug info down the bottom).  When I switched debug mode off again, it went back to normal, loading content etc perfectly. I suspect it's got something to do with the cache, but I'm having a hard time trying to nail it down as it's very intermittent - it has been working fine for the last few months, before that it was going down several times a day. 

The entire website was moved from a different server a few months ago and the problem stopped then.  This is the first time it has happened on the new server, but I doubt it's a server/memory issue.  The website gets a few hundred hits per day max (averages 500MB bandwidth a month total), it's not a media heavy website at all and its on a reasonable server.  The peaks in traffic do not correspond with the outages.  Plus - the admin sections works perfectly and going in and re-saving the template gets it running straight away.

It's a pretty frustrating issue - I have looked at all the PHP error logs, CMSMS admin logs, traffic logs, MySQL etc etc.. everything seems to be fine.  My suspicion is that it is cache and/or permissions related - for example CMSMS is saving a empty page as the cache and serving that as the main page (I haven't had a chance to try pages other than the main one when it's been down). 
Then when my client goes in and re-saves the template, or I turn on debug mode - the cache is manually cleared by that action and the page is re-created.

Does this sound reasonable?  If so how would I go about fixing this?  The permissions for tmp directory are currently set to 755.  Within that folder:
templates_c, cache & configs folders - permissions are 775
a bunch (5 or so) files called sess_3d495e7f34f95 etc are all 0 bytes with permissions set to 600.

As for versions - its CMS Made Simple 1.6.6, PHP 5.2.12, MySQL 5.0.90 on Apache/Linux.

Thanks.
Any help would be greatly appreciated.

[calguy1000]

I think your correct that it's a cache issue.

I would check for things like:
permissions:  777 permission is a safe bet.
  (do they change?  does your host have a cron job that resets permissions on a regular basis... keep an eye on them).
disk space
  - believe it or not, some hosts can run close to, or out of disk space

[pat11]

Good point - I hadn't thought of cron jobs.  That would explain quite a bit.  I set the tmp directory to 777 and will monitor it.

According to cPanel I have used a small fraction of my disk space - ~500 of 15000.  Is it possible/common for hosts to keep me 'on the edge' as it were (ie clearing disk space as I upload things)?  Is it worth getting in contact with them and mentioning it?  We have a good relationship with our host.


Thanks for the prompt reply!

[calguy1000]

cpanel will tell you your quota
but that is seperate from OS level disk quotas (I think)
and certainly different than physical space on the disk.

[alaw]

I have a client who is experiencing the same issue. I've been (temporarily) fixing it by manually clearing the cache in Site Admin/Global Settings/Advanced Setup. This site is running 1.6.6, but I think we've seen this in 1.7 as well.

So, if you figure out a solution to this problem, please update this post.

Thanks.

[alaw]

Just out of curiosity, who is your site hosted with? Ours is with GoDaddy. Just looking to see if there is a common thread...