Constant mpm_itk errors in Apache error log

apache-2.4

I have Apache 2.4 set up on a VPS serving 2 virtual hosts (one http and one https) for the same domain. Everything seems to be working fine except for these consistent lines in my apache error log (different pid's of course):

[mpm_itk:error] [pid 31830] child died with signal 11

These mpm_itk errors seem to occur in groups of 5 or 6 roughly every hour and every so often this happens:

[Fri Aug 07 06:25:14.440874 2015] [mpm_prefork:notice] [pid 470] AH00171: Graceful restart requested, doing restart
[Fri Aug 07 06:25:14.513782 2015] [mpm_prefork:notice] [pid 470] AH00163: Apache/2.4.10 (Debian) mpm-itk/2.4.7-02 OpenSSL/1.0.1k configured — resuming normal operations

Both Apache modules mpm_itk and mpm_prefork are enabled in my settings (or is this a problem in itself?).I am wondering if it is safe just to disable mpm_itk and restart Apache? Its a live ecommerce site and I need to be sure before I do anything that may make the problem worse. If anyone has any advice how to safely proceed it would be greatly appreciated.

update

Ok, I have disabled mpm_itk and restarted apache using mpm_prefork. The "mpm_itk errors" are now gone but I am getting these core notices instead :"AH00052: child pid xxxxx exit signal Segmentation fault (11)". Does anyone know what I should be looking at to finally fix this?

Best Answer

Mod ITK crash with incompatible modules, by example: mod security and others. In my case, y try a custom module but when enable it, itk crash with same error message.

Disable other modules and try restart server.

Related Solutions

Adding “URL” accessed to Apache Error log

taken from the debian apache2.conf default file:

# The following directives define some format nicknames for use with
# a CustomLog directive (see below).
# If you are behind a reverse proxy, you might want to change %h into %{X-Forwarded-For}i
#
LogFormat "%v:%p %h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" vhost_combined
LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
LogFormat "%h %l %u %t \"%r\" %>s %b" common
LogFormat "%{Referer}i -> %U" referer
LogFormat "%{User-agent}i" agent

See Apache 2 Manual for the meaning of the different format signs % or Apache 2 Manual ErrorlogFormat Directive for having the error log in a specific format since apache 2.4 aswell.

in short :

Define the output format in your main config file and the output file for example per vhost in the VirtualHost Directive. You can define the config file for all your sites in the main file aswell, if you want to.

something like would be needed to add (in case its not there yet):

    LogLevel warn

    CustomLog /var/log/apache2/access.log combined
    ErrorLog /var/log/apache2/error.log

Depending on your exact setup you might want to change the location slightly.

Dont forgot to logrotate them if you have a high traffic site.

Normally this should be (at least in debian) the default setting for how i remember it.

If you have empty logs you might want to check the permissions of the folder/files so that the user the apache2 process runs under can access and write to them.

Remember a reload of the process is (for what i know) needed for rereading the configuration files.

Linux – Error Log levels Apache 2.4

Setting Apache's logging verbosity

The detail of logging provided by Apache is controlled via the Loglevel directive. See the docs for details.

Set the value according to your needs, and run

service httpd restart

to apply.

There is no way to make Apache httpd change its verbosity while it's running, unfortunately.

Some modules (like mod_php, mod_log_forensics, mod_security) though have their own way of increasing their logs' detail level, please see the module's docs for those - some of those may allow increasing verbosity without restarting httpd (e.g. mod_php using php.ini for PHP errors).

With Apache httpd some of those (like mod_rewrite) directives were incorporated into the Loglevel directive and thus need httpd to be restarted.

Inspecting Apache's settings

If you want to know which directive has which value in a running apache instance, have a look at mod_info.

On RHEL, its output at http://host/server-info (you have to enable it first) looks like this:

In file: /etc/httpd/conf/httpd.conf
 260: ServerAdmin root@localhost
 283: UseCanonicalName Off
 290: DocumentRoot "/var/www/html"
 300: <Directory />
 301:   Options FollowSymLinks
 302:   AllowOverride None
    : </Directory>
 315: <Directory "/var/www/html">
 329:   Options Indexes FollowSymLinks
 336:   AllowOverride None
    : </Directory>
 407: AccessFileName .htaccess
 433: DefaultType text/plain
 453: HostnameLookups Off
 481: ErrorLog logs/error_log
 *488: LogLevel warn*
 533: ServerSignature On
 550: <Directory "/var/www/icons">
 551:   Options Indexes MultiViews
 552:   AllowOverride None
    : </Directory>
 579: <Directory "/var/www/cgi-bin">
 580:   AllowOverride None
 581:   Options None
    : </Directory>
 756: AddDefaultCharset UTF-8
 850: <Directory "/var/www/error">
 851:   AllowOverride None
 852:   Options IncludesNoExec
    : </Directory>