Web Agent Guides › Web Agent Configuration Guide › Basic Agent Setup and Policy Server Connections › Manage Web Agents with Multiple Web Server Instances

Manage Web Agents with Multiple Web Server Instances

If you configure a Web Agent on multiple web server instances, each server instance requires its own Web Agent cache, log file, and health monitoring resources. To verify that resources are unique, configure the following parameter in the WebAgent.Conf file:

ServerPath

Specifies a unique path to each web server instance when a Web Agent is configured to use multiple instances of a web server. The ServerPath creates a unique identifier for the caching, logging, and health-monitoring resources that the agents use.

This value must be an alphanumeric string unique among server instances running on the system. For example, if you have two server instances, the value of the ServerPath parameter for one instance could be MyAgent1 and the value for the second instance could be MyAgent2.

Default: Empty

Example: If there are four web server instances, each loading an agent, then set the ServerPath parameter in the WebAgent.conf file of each server instance to a unique value. You can set the ServerPath parameter to the directory where the log file of each server instance is stored, such as server_instance_root/logs.

To configure a Web Agent on multiple server instances, add a unique path to the ServerPath parameter in each WebAgent.conf file.

Set the ServerPath Parameter for Windows Systems

If there are multiple server instances in your Windows operating environment, specify a value for the following parameter in the WebAgent.conf file:

ServerPath

Specifies a unique path to each web server instance when a Web Agent is configured to use multiple instances of a web server. The ServerPath creates a unique identifier for the caching, logging, and health-monitoring resources that the agents use.

This value must be an alphanumeric string unique among server instances running on the system. For example, if you have two server instances, the value of the ServerPath parameter for one instance could be MyAgent1 and the value for the second instance could be MyAgent2.

Default: Empty

Example: If there are four web server instances, each loading an agent, then set the ServerPath parameter in the WebAgent.conf file of each server instance to a unique value. You can set the ServerPath parameter to the directory where the log file of each server instance is stored, such as server_instance_root/logs.

Note: Do not use a backslash (\) in the string you specify for the ServerPath parameter; all other characters are permitted.

The ServerPath parameter is not required for the following Windows platforms:

• IIS servers (there is always only one server instance).
• Apache 2.0 servers if there is only one web server instance. The parameter is supported on these systems, but it serves no purpose.
• The Oracle iPlanet or Domino web servers.

  These servers do not run in multiprocess mode on Windows.

Set the ServerPath Parameter for UNIX Systems

The ServerPath parameter is located in the WebAgent.conf file.

For web servers on UNIX platforms, we recommend that each server instance has its own Agent resources.

Set the ServerPath parameter for the following servers on UNIX:

• Any Apache 2.0 (including any Apache 2.0-based servers, such as IBM HTTP Server)
• Any Oracle iPlanet web server instance

Note: The ServerPath is not required for Domino web servers on UNIX systems.

The value you set for the ServerPath parameter must be an alphanumeric string unique among the server instances running on the system. For example, if you have two server instances, the value of the ServerPath parameter for one instance could be MyAgent1 and the value for the second instance could be MyAgent2.

Additional Configurations Requiring the ServerPath Parameter

The following list describes other use cases for requiring the ServerPath parameter:

• The Web Agent tracks shared memory using a semaphore. A semaphore is a value in operating system (or kernel) storage. Process running on the system examine this value to verify resource availability. Because the semaphore is not unique, multiple Agents would try to point to the same area of memory. Naming a server path gives the root of an instance, and the Agent finds the files that are used for creating unique keys for semaphores.
• For multiple server instances (all platforms except Windows), the Agent fails to execute one of the following operations:
  • To encrypt value of the AgentName parameter (00-0012 error).
  • To encrypt SMSESSION or SMIDENTITY cookies.
  • To update the agent encryption keys when the agent starts.
• With Apache (all platforms except Windows), the Agent does not release its six shared memory segments (semaphores) when Apache is restarted.
• If each Web Agent is configured for a different web server type on the same system, such as an Apache 2.0 server and an Oracle iPlanet server. Specify a unique ServerPath value for the configuration of each server. Different web server types cannot share agent resources.