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I have a Magento installation running on x-large Amazon server. I have Varnish, memcached and eAccelerator installed on the server. At first everything was working fine, but then at some point it stopped working, throwing 503 error with Varnish cache stamp below it. When I disable eaccelerator, error is gone and site is working. This is my eaccelerator config:

eaccelerator.shm_size = "512"
eaccelerator.cache_dir = "/var/cache/php-eaccelerator"
eaccelerator.enable = "1"
eaccelerator.optimizer = "1"
eaccelerator.debug = 0
eaccelerator.log_file = "/var/log/httpd/eaccelerator_log"
eaccelerator.name_space = ""
eaccelerator.check_mtime = "1"
eaccelerator.filter = ""
eaccelerator.shm_ttl = "0"
eaccelerator.shm_prune_period = "0"
eaccelerator.shm_only = "0"
eaccelerator.allowed_admin_path = ""

any hints?

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Is it Varnish throwing the 503, or the application? – pkhamre Oct 24 '12 at 10:53
I think it's Varnish. Application is unreachable, as phpinfo() file is also unavailable – srgb Oct 24 '12 at 10:54
Can you try to issue a request directly to Apache without going through Varnish? – pkhamre Oct 24 '12 at 10:55
I don't know how to do that :/ – srgb Oct 24 '12 at 10:55
Maybe. Check if you can find your Apache logs and see if you find anything related in the errorlog. – pkhamre Oct 24 '12 at 12:06
up vote 1 down vote accepted

Problem was caused by the fact that kernel allowed only 32M of shared memory, as defined in /proc/sys/kernel/shmmax , while I was trying to allocate 512M.

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