How to debug solve 500 Internal error aws micro ec2 with suexec, Apache and php CGi

Question

I'm running WordPress multi-site on an amazon micro ec2 with suexec, Apache and php CGi On Ubuntu 12.04 However I've been experiencing a lot of Internal server 500 errors and I'm in the process of debugging it to find a solution. I've posted my error logs below

example.com error.log:

[Fri Oct 26 10:10:08 2012] [warn] [client 23.23.xxx.xx] (104)Connection reset by peer: mod_fcgid: error reading data from FastCGI server
[Fri Oct 26 10:10:08 2012] [error] [client 23.23.xxx.xx] Premature end of script headers: wp-cron.php
[Fri Oct 26 10:50:04 2012] [warn] [client 190.213.xxx.xxx] (104)Connection reset by peer: mod_fcgid: error reading data from FastCGI server, referer: https://www.example.com/wp-admin/
[Fri Oct 26 10:50:04 2012] [error] [client 190.213.xxx.xxx] Premature end of script headers: admin.php, referer: https://www.example.com/wp-admin/
[Fri Oct 26 10:58:14 2012] [warn] [client 190.213.xxx.xxx] (104)Connection reset by peer: mod_fcgid: error reading data from FastCGI server, referer: https://www.example.com/wp-admin/network/index.php
[Fri Oct 26 10:58:15 2012] [error] [client 190.213.xxx.xxx] Premature end of script headers: admin-ajax.php, referer: https://www.example.com/wp-admin/network/index.php
[Fri Oct 26 10:58:56 2012] [warn] [client 190.213.xxx.xxx] (104)Connection reset by peer: mod_fcgid: error reading data from FastCGI server, referer: https://www.example.com/wp-admin/network/index.php
[Fri Oct 26 10:58:57 2012] [error] [client 190.213.xxx.xxx] Premature end of script headers: plugins.php, referer: https://www.example.com/wp-admin/network/index.php
[Fri Oct 26 10:59:18 2012] [warn] [client 190.213.xxx.xxx] (104)Connection reset by peer: mod_fcgid: error reading data from FastCGI server, referer: https://www.example.com/wp-admin/network/index.php
[Fri Oct 26 10:59:18 2012] [error] [client 190.213.xxx.xxx] Premature end of script headers: admin-ajax.php, referer: https://www.example.com/wp-admin/network/index.php
[Fri Oct 26 11:01:49 2012] [warn] [client 190.213.xxx.xxx] (104)Connection reset by peer: mod_fcgid: error reading data from FastCGI server, referer: https://www.example.com/wp-admin/
[Fri Oct 26 11:01:49 2012] [warn] [client 190.213.xxx.xxx] (104)Connection reset by peer: mod_fcgid: ap_pass_brigade failed in handle_request_ipc function, referer: https://www.example.com/wp-admin/

Apache Log:

php (pre-forking): Cannot allocate memory
php (pre-forking): Cannot allocate memory
Recipient names must be specified
Recipient names must be specified
php (pre-forking): Cannot allocate memory
php (pre-forking): Cannot allocate memory
php (pre-forking): Cannot allocate memory
[Fri Oct 26 10:49:33 2012] [warn] mod_fcgid: cleanup zombie process 2852
[Fri Oct 26 10:49:33 2012] [warn] mod_fcgid: cleanup zombie process 2851
[Fri Oct 26 10:49:33 2012] [warn] mod_fcgid: cleanup zombie process 2853
[Fri Oct 26 10:58:22 2012] [warn] mod_fcgid: process 2892 graceful kill fail, sending SIGKILL
php (pre-forking): Cannot allocate memory
[Fri Oct 26 10:59:21 2012] [warn] mod_fcgid: process 2894 graceful kill fail, sending SIGKILL
[Fri Oct 26 10:59:25 2012] [warn] mod_fcgid: process 2866 graceful kill fail, sending SIGKILL

suexec.log:

[2012-10-25 16:05:36]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi
[2012-10-25 18:09:38]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi
[2012-10-25 18:09:51]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi
[2012-10-25 18:14:03]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi
[2012-10-25 18:14:06]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi
[2012-10-25 18:14:35]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi
[2012-10-25 20:20:27]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi
[2012-10-25 20:20:29]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi
[2012-10-25 20:20:31]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi
[2012-10-25 21:42:12]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi
[2012-10-25 22:56:50]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi
[2012-10-26 02:34:43]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi
[2012-10-26 04:25:07]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi
[2012-10-26 06:35:19]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi
[2012-10-26 06:40:05]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi
[2012-10-26 07:22:45]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi
[2012-10-26 10:10:05]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi
[2012-10-26 10:49:24]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi
[2012-10-26 10:49:24]: uid: (1002/username) gid: (1002/username) cmd: php-fcgi

based on the logs can any determine what might be the cause of this? Thinking that it might be the micro instance I'm thinking of upgrading to a small.

Any help would be greatly appreciated.

This is the output after typing free -m

             total       used       free     shared    buffers     cached
Mem:           590        583          6          0          2         22
-/+ buffers/cache:        559         30
Swap:            0          0          0

Answer 1

I Upgraded from a Miro instance to a Small instance which seems to have solved the problem no more 500 errors.

It appears that the Miro instance doesn't have enough memory to effectively operate WordPress Multi-Site on a consistent bases.

Answer 2

If you're feeling like having a super-slow server, you can add another EBS and use it as swap.

Otherwise you can try reducing php memory limit (it's set in php.ini), removing unused php extensions, or migrating to something more lightweight like nginx+php-fpm.