Site Down 36 Hours : How I Fixed Internal Server Errors

If you visited this blog in the last 2 days, there is a good chance you got Internal server errors and Server 500 Errors on every page of this blog. The main domain name was active, so was my wordpress admin screens, but there was no connectivity between them causing those server errors.

Web Host Responses

I managed to get 2 responses from my web hosting Dreamhost at 24 hourly response intervals. The first response was something like “I restarted the mysql service as your site was not able to connect to the database”. But nothing happened and a second response 24 hours later pointed me to install a wordpress plugin to fix the server 500 issue (the same that fixed server 500 errors with WordPress 2.0.5 upgrades). I upgraded to WordPress 2.0.5 over a month back and if I did not require that plugin then, then why now. Still I installed the plugin, but nothing happened as I expected.

Fixing internal server errors

So I decided that I myself had to figure out a way to fix it or face more site downtime. I claim to be no expert at this, but this is just the way I approached the issue and you can see the blog online now.

Firstly I fixed up the main index page. For the first time I was truly glad I hosted WordPress in an alternative directory. I could easily add any index.html file via FTP and override the default page index.php that wordpress had configured to show on the main domain name. So I was able to restore the index page and post a notice about the errors, point readers to subscription options and my other related services.

Fixing WordPress

It became clear that it was a WordPress issue since the rest of the site was functioning well. Since I was using the lastest WordPress version, and had not changed any default wordpress configurations or modified wordpress admin files recently, the core wordpress installation was not at fault.

So I narrowed down to any plugins I had installed recently which might be causing the error. I had installed the WP-PageNavi plugin that adds a more advanced page navigation to WordPress a few hours back, but it was working fine thereafter. I tried disabling it, but still no response.

Then I disabled all the wordpress plugins one by one and activated them again one by one to see if this would work. And guess what I identified the buggy plugin – WP-Cache.

I had installed WP-Cache recently to prevent server crashes due to recent site traffic surges. It is an amazing plugin with a very fast cache module, that delivers the web pages from the cache rather than reloading the full page and helps to reduce the server load.

I disabled WP-cache from the WP-cache manager. It showed 314 cached and 314 expired pages. I tried to delete the expired and cached pages but it would not let me. Finally after a few times, I clicked the “restore default configuration” button (though I had never changed the options before) and was able to clear the cache after that. The blog went live instantly and all internal server errors disappeared. I have the latest version of WP-cache, but the instant I activate it, the errors are back. So till I figure it out, I need to disable caching.

Getting Back Online

I quickly renamed the index.html or some other name and the preexistent index.php became the default page again on the domain name. All plugins excluding WP-Cache are well and working.

Lessons learnt

If you analyse the problem well enough, you can find the solution yourself. You need not be an expert on the topic. Depend on professional support, but they take time, are tired by complaints throughout the day, have hundreds of open tickets to close and it may not be their area of expertise. You maybe smarter and have access to password protected options and settings that they don’t have (like plugin controls). I don’t say this will work every time, but had I not stepped in, you might not be reading this post for a few more days…


  1. rakesh says:

    Are u sure u fixed the problem, i just got a internal server 500 error. I think u haven’t learnt ur lesson properly. :D

  2. Sweta says:

    Error 500 is generated by webserver. I have not 1 but 15 blogs running using wp-cache and wordpress 2.5. Ask your service provider to fix this or move to other good service provider.

    Just search using google “http error 500 php”

  3. QuickOnlineTips says:

    I am no expert in web servers as I have clearly mentioned in this post. I am just another wordpress blogger like most others.

    This post just shows my attempt to fiddle with my wordpress settings (when the site was down so long and webhosting support could not fix the issue). I tried disabling WP-cache and the errors were gone and blog went online instantly. I tried this out and it worked for me. :-)

    Thanks for pointing out that link. I am sure the readers will learn more ways to fix such errors.

  4. QuickOnlineTips says:

    I am not getting any 500 errors now. Are you still getting them?

  5. Borbs says:

    I am getting this problem, too. For some reason, I just need to delete the wp_cache_mutex.lock and the site is back on track.

    I wish it never happens anymore… But I do know how… =/

  6. QuickOnlineTips says:

    I deleted the wp_cache_mutex.lock which was found in Cache folder. But it still does not work. Instant internal server errors. What does this wp_cache_mutex.lock file do? I see it is edited out by comments in wp-cache-phase2.php

  7. Sharon - Linux hosting says:

    Contact your server administrator or your web hosting company and they will fix it for you

  8. Lovedeep Wadhwa says:

    I encountered this problem today. Luckily i remembered about this post.

    Deleting the cache files and the wp_cache_mutex.lock file solved the problem.

    Thanks. :D

  9. Vincent Chow says:

    I think this only happens on WordPress hosted on DreamHost. I’m using DreamHost too and faced this problem since long ago. It’s due to wp-cache. Yesterday it occur again, and after experimenting, the problem is gone.

    I think DreamHost realize this problem as many DreamHost users sent them the problem. But they just don’t bother to do something.

  10. j says:

    I have just installed WP-Cache and was happy to finally get it working. Right after i started getting 500 errors. So i knew something was up. After doing some research i found out that all people with have this problem and can not fix it. I tried deleting the wp_cache_mutex.lock file and all that but the problem just wont go away.

    So far I’m told there is no solution. But nice post i found it on google. just thought i would leave that has a problem as well.

  11. videokeman says:

    funny i was having the same problem too with the mutex lock, i changed host was succesful to migrate everything. but when i enable wp-cahe im having the mutex lock error. has any one found a solution for this?

  12. J says:

    if your new host is godaddy then there is no fix currently because its a problem with the host.

  13. Beetlejuice says:

    Dreamhost have a fix for this problem in their Help pages:

    1. Open /wp-content/plugins/wp-cache/wp-cache-phase2.php file* in your favourite text editor, where is the domain that you’re having troubles with EG:
    2. Alternatively if that file is not in that location for some reason you can issue this command to find it from the directory: find . -name wp-cache-phase2.php
    3. Locate the wp_cache_ob_end function
    4. then inside that function find the line with: ob_end_clean(); (it should be line 219 or about)
    5. and finally replace that line with: ob_end_flush();

  14. Bill says:

    Beetlejuice – that is a different problem… blank pages is a totally different issue.

    This is a new problem which has cropped up with Dreamhost (and maybe others)… and hard to believe but no solutions can be found.

    This error will cause your entire blog to be down and usually will spit out ugly error messages on your home page that look something like…

    blah blah wp-cache-phase2.php on line 96

  15. Web Tech says:

    I even can;t access the wp dashboard. Then I delete wp_cache_mutex.lock at wp-content/cache. And it works perfectly, thx

  16. Susan says:

    I can’t even get to my admin panel to do any of this. I can only get to the file manager.

    Yahoo tech won’t help – it isn’t their product.

    What can I do?

  17. Susan says:

    Because I am unable to get into my admin area, I cannot disable the stupid cache and even though I have deleted all cached files and the wp_cache_mutex.lock over and over again…everytime I try to view my page, the wp_cache_mutex.lock file reappears in the file manager!!!

    Does anyone know how to get rid of it?

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