Configuring the MPM used in an HTTPD instance of vFabric Enterprise Ready Server

Products

• Pivotal Web Server

Issue/Introduction

On Unix/Linux platforms, vFabric Enterprise Ready Server (ERS) HTTPD instances can be configured to use either the worker or prefork multi-processing modules.

Note: This article is not applicable to Windows, MPM is always set to mpm_winnt on Windows.

Resolution

There is a different executable for each MPM, therefore the startup script (apache_startup.sh) must know which to invoke at startup and shutdown. The script contains a default value for the system, but it reads the instance conf/startup.properties file for the default_mpm variable, which overrides the script default.

The default httpsd.conf file supplied contains configuration parameters for both MPMs - for prefork in the <IfModule prefork.c> section and worker in the <IfModule worker.c> section. The section that matches the configured MPM to be used. You may need to adjust these parameters according to your intended use.

To modify the MPM in use by the instance, perform these steps:

1. Ensure that the appropriate MPM-specific parameters are present in the conf/httpsd.conf file.
2. Make sure the instance is not running (bin/apache_startup.sh stop if needed).
3. Modify the default_mpm value specified in conf/startup.properties (prefork or worker are valid).
4. Start the instance again if required (run bin/apache_startup.sh start to start the instance )

Additional Information

• Apache HTTPD prefork MPM parameters: http://httpd.apache.org/docs/2.2/mod/prefork.html
• Apache HTTPD worker MPM parameters: http://httpd.apache.org/docs/2.2/mod/worker.html

Note: Apache HTTPD 1.3 does not have the option of the worker MPM.