How to Enable Event MPM in Apache on CentOS/RHEL

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Apache HTTP Server, one of the most widely used web servers globally, has the power to handle several clients concurrently. It accomplishes this via various Multi-Processing Modules (MPMs), affecting how Apache responds to network traffic. One such MPM, the Event MPM, is known for its high performance and ability to handle numerous simultaneous connections with minimal memory usage.

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This article will guide you through the steps required to enable Event MPM in Apache on CentOS/RHEL.

Prerequisites

Before we start, ensure you have:

  • CentOS/RHEL installed on your server
  • Sudo or root privileges to run administrative commands
  • Apache HTTP server installed

Step-by-Step Guide

Here are the steps to enable Event MPM in Apache:

Step 1: Checking the Current MPM

Start by checking which MPM is currently enabled in your Apache HTTP server. Use the following command:

httpd -V | grep MPM

This will display the current MPM in use. By default, the pre-fork MPM is usually enabled.

Step 2: Installing Event MPM

If the Event MPM isn’t enabled, you need to install it. Apache in CentOS/RHEL has a package that allows for easy installation. Use the following command to install:

sudo yum install httpd-event

This will install the Event MPM.

Step 3: Disabling the Current MPM

After installing the Event MPM, you need to disable the currently enabled MPM (usually pre-fork or worker). Open the Apache configuration file with a text editor:

sudo nano /etc/httpd/conf.modules.d/00-mpm.conf

Comment out the line of the currently enabled MPM, and uncomment the line for event MPM. The configuration should look like this:

Save the file and exit the text editor.

Step 4: Restarting Apache

To implement the changes, you need to restart the Apache HTTP server. Use the following command:

sudo systemctl restart httpd

Step 5: Verifying the Changes

You can verify if Event MPM is enabled by running the following command:

httpd -V | grep MPM 

Output:

Server MPM:     event

This should now show that the Event MPM is enabled.

Conclusion

With this, you have successfully enabled the Event MPM in Apache on CentOS/RHEL. Event MPM can significantly improve your server’s performance, especially if it serves high-traffic websites. However, it’s also crucial to monitor and tweak your server settings as per your specific use case to ensure optimal performance.

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4 Comments

  3. Pete Long on

    Hi If I do this Apache fails and will not start till I change it back? (CentOS7)

    [root@pnl-server1 ~]# service httpd status
    Redirecting to /bin/systemctl status httpd.service
    ● httpd.service – The Apache HTTP Server
    Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled; vendor preset: disabled)
    Active: failed (Result: exit-code) since Wed 2016-01-13 11:10:50 EST; 3min 19s ago
    Docs: man:httpd(8)
    man:apachectl(8)
    Process: 151 ExecStop=/bin/kill -WINCH ${MAINPID} (code=exited, status=1/FAILURE)
    Process: 122 ExecStart=/usr/sbin/httpd $OPTIONS -DFOREGROUND (code=exited, status=1/FAILURE)
    Main PID: 122 (code=exited, status=1/FAILURE)

    Jan 13 11:09:44 pnl-server1.petenetlive.com systemd[1]: httpd.service failed.
    Jan 13 11:10:50 pnl-server1.petenetlive.com systemd[1]: Starting The Apache HTTP Server…
    Jan 13 11:10:50 pnl-server1.petenetlive.com httpd[122]: AH00526: Syntax error on line 31 of /etc/httpd/conf.d/php.conf:
    Jan 13 11:10:50 pnl-server1.petenetlive.com httpd[122]: Invalid command ‘php_value’, perhaps misspelled or defined by a module not included in the server configuration
    Jan 13 11:10:50 pnl-server1.petenetlive.com systemd[1]: httpd.service: main process exited, code=exited, status=1/FAILURE
    Jan 13 11:10:50 pnl-server1.petenetlive.com kill[151]: kill: cannot find process “”
    Jan 13 11:10:50 pnl-server1.petenetlive.com systemd[1]: httpd.service: control process exited, code=exited status=1
    Jan 13 11:10:51 pnl-server1.petenetlive.com systemd[1]: Failed to start The Apache HTTP Server.
    Jan 13 11:10:51 pnl-server1.petenetlive.com systemd[1]: Unit httpd.service entered failed state.
    Jan 13 11:10:51 pnl-server1.petenetlive.com systemd[1]: httpd.service failed.
    Hint: Some lines were ellipsized, use -l to show in full.
    [root@pnl-server1 ~]# nano /etc/httpd/conf.d/php.conf
    [root@pnl-server1 ~]#
    [root@pnl-server1 ~]#
    [root@pnl-server1 ~]# nano /etc/httpd/conf.modules.d/00-mpm.conf
    [root@pnl-server1 ~]# service httpd start
    Redirecting to /bin/systemctl start httpd.service
    [root@pnl-server1 ~]# service httpd status
    Redirecting to /bin/systemctl status httpd.service
    ● httpd.service – The Apache HTTP Server
    Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled; vendor preset: disabled)
    Active: active (running) since Wed 2016-01-13 11:16:22 EST; 5s ago
    Docs: man:httpd(8)
    man:apachectl(8)
    Process: 151 ExecStop=/bin/kill -WINCH ${MAINPID} (code=exited, status=1/FAILURE)
    Main PID: 710 (httpd)
    Status: “Processing requests…”
    CGroup: /system.slice/httpd.service
    ├─710 /usr/sbin/httpd -DFOREGROUND
    └─712 /usr/sbin/httpd -DFOREGROUND

    Reply
    • furriephillips on

      I had the same, but when checking the apache config for syntax errors, I got this

      # apachectl configtest
      AH00526: Syntax error on line 34 of /etc/httpd/conf.d/php.conf:
      Invalid command ‘php_value’, perhaps misspelled or defined by a module not included in the server configuration

      and the httpd server started up fine, after I’d commented out the 3 lines with that problem config variable

      #
      # Apache specific PHP configuration options
      # those can be override in each configured vhost
      #
      #php_value session.save_handler “files”
      #php_value session.save_path “/var/lib/php/session”
      #php_value soap.wsdl_cache_dir “/var/lib/php/wsdlcache”

      Reply

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