Jason Bennett's picture

Good morning. I installed the Moodle Appliance a couple weeks ago and migrated an existing Moodle (~20GB worth of data and a 100mb database) to it along with upgrading to the latest version of Moodle. It's running on a VMWare ESXi server. I did have to increase the size of the disk but that seemed to go fine.

This was all working fine for a few days. Then I went back in and when I attempt to load the site, I get a blank page. Chrome gives the error: "Error code: ERR_EMPTY_RESPONSE". The only page that loads is the login page @ hostname.of.moodle/login but when you attempt to login, it goes to the blank page again.

When I try to load the site, I get this entry in the apache error.log:
[Mon Jul 07 08:06:09 2014] [notice] child pid 13311 exit signal Segmentation fault (11)

I got it to work again by reinstalling Moodle (wiped out the moodle directory and uploaded the latest version) -- Ran setup, it linked back up to the db & data and was working again last week. I just checked again this morning and it's down.

Any idea what's going on here?

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Liraz Siri's picture

What process is crashing. Is it the same process. You list it as being pid 13311 but what program is that?

Anyhow, segmentation faults can happen for many reasons inclding:

  • faulty RAM
  • a software bug (more common in C programs than a PHP program)
  • a deliberate exploitation/denial of service attempt (this shouldn't be an issue as long as you didn't disable the security updates though)

If I had to guess I'd say faulty RAM is the most likely culprit. Last time I had random segmentation faults on a server I eventually traced it down to that.

r0b0-tr0n's picture

I experienced the same symptoms after manually installing Moodle 2.7.1+ on a fresh TK LAMP. Worked fine immediately after install but started having problems at next boot.

Did some debugging, long story short I was able to fix by changing xcache.cacher to Off in /etc/php5/apache2/conf.d/20-xcache.ini and restarting Apache.

Jason Bennett's picture

:-O Holy crap that worked!

Can I buy you a beer/coffee/cronut?

r0b0-tr0n's picture

I'll take a coffee :)

Jeremy Davis's picture

As it happens, newer versions of Moodle actually don't work with xcache at all. It didn't occur to me that that would be an issue with the (older) version included in TKL.

For later versions of Moodle, they recommend optcache be used instead. If you want to set that up, I documented it on another thread. Have a look at this post (about 1/3 of the way down, with the paragraph that starts "It all appeared to go well But after I did that Apache kept segfaulting (Chrome was reporting "No data recieved")... ").

Jason Bennett's picture

If you setup a contact form in your settings here or let me know some other send it, I'll send you a few $s for itunes/google play/amazon -- whatever works best. I work in edu so I can't offer a whole lot but you took a huge weight off my shoulders and I really appreciate it.

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