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Gaia
Asked: 2013-10-31 20:29:39 +0800 CST

How to troubleshoot occasional Apache 500 errors?

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I have GET and POST requests, both HTTP 1.0 and 1.1, to diverse URLs, mostly running Wordpress(1), which occasionally fail with a 500(2). No user has ever encountered a 500 themselves, nor have visitors ever reported one. But they do show up in the logs. Most of the time, the error is in connection with a bot request (decent bots too, including googlebot, bingbot). All User-Agents that do not seem to be a bot include the Linux string.

The only common thread I can infer across all these 500s is the bot/linux UAs connection.

What else could I try in order to figure out why these specific requests are failing?

16Gb RAM (rarely uses up more than 3GB)
8 cores, rarely goes above 0.50
Apache 2.2.15
mod_fgcid 2.3.7
CentOS 6.4
Kernel 2.6.32

TimeOut 60
KeepAlive on
MaxKeepAliveRequests 100
KeepAliveTimeout 5

<IfModule prefork.c>
StartServers       2
MinSpareServers    2
MaxSpareServers   5
ServerLimit      120
MaxClients      120
MaxRequestsPerChild  4000
</IfModule>

Loaded Modules:
 core_module (static)
 mpm_prefork_module (static)
 http_module (static)
 so_module (static)
 auth_basic_module (shared)
 auth_digest_module (shared)
 authn_file_module (shared)
 authn_alias_module (shared)
 authn_anon_module (shared)
 authn_dbm_module (shared)
 authn_default_module (shared)
 authz_host_module (shared)
 authz_user_module (shared)
 authz_owner_module (shared)
 authz_groupfile_module (shared)
 authz_dbm_module (shared)
 authz_default_module (shared)
 include_module (shared)
 log_config_module (shared)
 env_module (shared)
 ext_filter_module (shared)
 mime_magic_module (shared)
 expires_module (shared)
 deflate_module (shared)
 headers_module (shared)
 setenvif_module (shared)
 mime_module (shared)
 autoindex_module (shared)
 vhost_alias_module (shared)
 negotiation_module (shared)
 dir_module (shared)
 actions_module (shared)
 speling_module (shared)
 alias_module (shared)
 substitute_module (shared)
 rewrite_module (shared)
 cache_module (shared)
 suexec_module (shared)
 disk_cache_module (shared)
 cgi_module (shared)
 version_module (shared)
 cloudflare_module (shared)
 sed_module (shared)
 security2_module (shared)
 unique_id_module (shared)
 fcgid_module (shared)
 evasive20_module (shared)
 php5_module (shared)
 ssl_module (shared)

1) Some of these Wordpress sites are running W3TC, others are not. Some vhosts are running Magento, but they get so few 500s I'm gonna write them off as bad requests.

2) I have setup log monitoring and I get emailed when 500s occur.

PS: If this question gets moved to Wordpress.SO or Webmasters.SO I might as well delete it. I will never get a decent answer there...

apache-2.2

0 Answers