Questions[drupal](server)

We're running a heavy Drupal website that performs financial modeling. We seem to be running into some sort of memory leak given the fact that overtime the memory used by apache grows while the number of apache processes remains stable:

We know the memory problem is coming from apache/PHP because whenever we issue a /etc/init.d/httpd reload the memory usage drops (see above screenshot and below CLI outputs):

Before httpd reload

$ free
             total       used       free     shared    buffers     cached
Mem:      49447692   45926468    3521224          0     191100   22609728
-/+ buffers/cache:   23125640   26322052
Swap:      2097144     536552    1560592

After httpd reload

$ free
             total       used       free     shared    buffers     cached
Mem:      49447692   28905752   20541940          0     191360   22598428
-/+ buffers/cache:    6115964   43331728
Swap:      2097144     536552    1560592

Each apache thread is assigned a PHP memory_limit of 512MB which explains the high memory usage depiste the low volume of requests, and a max_execution_time of 120 sec which should terminate threads which execution is taking longer, and should therefore prevent the constant growth in memory usage we're seeing.

Q: How could we investigate what is causing this memory leak?

Ideally I'm looking for troubleshooting steps I can perform on the system without having to bother the dev team.

Additional info:

OS: RHEL 5.6
PHP: 5.3
Drupal: 6.x
MySQL: 5.6

FYI we're aware of the swapping issue which we're investigating separately and has nothing to do with the memory leak which we've observed before the swapping started to occur.

I'm trying to get an overview of how i would go about creating a load balanced web server setup. Setting up the actual load balancer and adding two or more web servers seems fair enough. However, I can't decide what the best setup for files would be.

The web servers will be running a CMS system (in this case Drupal). There might be files uploaded by users which relates to content, and this should be accessible to all web servers. Now, I was thinking of simply having a designated file server and mount a file directory on each web server so that the various web servers could access these "shared" files.

However, would this solution be a bottleneck if we're talking about 4-5 servers? I'd think the mounting would be done over SSH.

All help highly appreciated!

Update (January 15, 2013)

I decided to go with a combination of Csync2 and Lsyncd. I then set up two servers which acts as mirrors. Lsyncd listens for changes in certain directories (and their subdirectories) and invokes Csync2 which takes care of synchronizing files to the other server. If you're interested in knowing more, have a look at this tutorial.

I installed multiple drupal 7 sites using the Web Platform Installer on Windows Server 2008.

Until know they worked without any problems, but recently internal server error 500 started to show up (once every so many requests), now it happens for all requests to any of the php sites.

There's not much detail to go on, and nothing changed between the time when it was working and now (well nothing I know of anyway)

The log file is flooded with messages such as

[09-Aug-2011 09:08:04] PHP Fatal error:  Allowed memory size of 262144 bytes exhausted (tried to allocate 261904 bytes) in Unknown on line 0
[09-Aug-2011 09:08:16] PHP Fatal error:  Allowed memory size of 262144 bytes exhausted (tried to allocate 261904 bytes) in Unknown on line 0
[09-Aug-2011 09:08:16] PHP Fatal error:  Allowed memory size of 262144 bytes exhausted (tried to allocate 261904 bytes) in Unknown on line 0
[09-Aug-2011 09:08:20] PHP Fatal error:  Allowed memory size of 262144 bytes exhausted (tried to allocate 261904 bytes) in Unknown on line 0
[09-Aug-2011 09:08:22] PHP Fatal error:  Allowed memory size of 262144 bytes exhausted (tried to allocate 261904 bytes) in Unknown on line 0
[09-Aug-2011 09:08:51] PHP Fatal error:  Allowed memory size of 262144 bytes exhausted (tried to allocate 261904 bytes) in Unknown on line 0
[09-Aug-2011 09:09:56] PHP Fatal error:  Allowed memory size of 262144 bytes exhausted (tried to allocate 261904 bytes) in Unknown on line 0
[09-Aug-2011 09:09:57] PHP Fatal error:  Allowed memory size of 262144 bytes exhausted (tried to allocate 261904 bytes) in Unknown on line 0
[09-Aug-2011 09:12:13] PHP Fatal error:  Allowed memory size of 262144 bytes exhausted (tried to allocate 261904 bytes) in Unknown on line 0
[09-Aug-2011 09:15:09] PHP Fatal error:  Allowed memory size of 262144 bytes exhausted (tried to allocate 261904 bytes) in Unknown on line 0
[09-Aug-2011 09:15:09] PHP Fatal error:  Allowed memory size of 262144 bytes exhausted (tried to allocate 261904 bytes) in Unknown on line 0
[09-Aug-2011 09:21:28] PHP Fatal error:  Allowed memory size of 262144 bytes exhausted (tried to allocate 261904 bytes) in Unknown on line 0
[09-Aug-2011 09:21:28] PHP Fatal error:  Allowed memory size of 262144 bytes exhausted (tried to allocate 261904 bytes) in Unknown on line 0

I have tried increasing the memory limit in php.ini as such:

memory_limit = 512MB

But that doesn't seem to solve the problem either.

This is in the global php configuration in IIS When I looked at the sites one by one, I noticed that PHP seemed to have been disabled.

PHP is not enabled. Register new PHP version to enable PHP via FastCGI

So I tried to register the php version again

C:\Program Files\PHP\v5.3\php-cgi.exe

But when I try to apply the changes I get

There was an error while performing this operation Details: Operation is not valid due to the current state of the object

There doesn't seem to be any other information than that. I have no idea why all of a sudden php isn't available for the sites anymore.

PS: I have rebooted IIS, the server, etc... This server is hosted on amazon S3, so I gave the server some more power

Update These seem to be two different issues

1. I used memory_limit=128MB instead of memory_limit=128M
   Notice the "M" instead of "MB"
2. A memory_limit of 128M was not enough, had to increase it to 512M

The first issue caused internal server errors for every request.

Increasing to 512MB seemed to have solved the problem for a little while, but after a while the server errors return. Note that the PHP manager inside of IIS still shows there is no PHP available for the sites (the global config does see it as available)

So the problem remains unsolved

Here is the problem: I have a Linux server in Europe serving a busy Drupal site using nginx+php-fpm, I have another Linux server in the US (where a big portion of my visitors are coming from). The second server is heavily under-used. I am wondering how to make use of the second server to deliver my site's static content?

I'm setting up a large Drupal (Pressflow) site and this is my current plan. Have I gone and done anything blatantly stupid? Does anyone have any experience hosting a large, multi-server Drupal installation like this?