The WLOC environment includes one or more Agents that manage the resources that are available to services and communicate this information to the Controller. To manage resources, an Agent performs the following tasks:
Provides ongoing visibility into the amount of resources that WLOC is using for a given resource pool.
Controls the life cycle of JVMs in a resource pool upon request from the Controller.
Monitors the health of instantiated JVMs, gathering metrics, and monitoring data for use by the Controller in its evaluation of policies.
Types of Agents
WLOC enables you to define two types of agents:
|Type of Agent||Description|
Manages the computing resources for the physical machine on which the Agent is installed. You can configure a plain Agent to allocate all or a subset of the available machine resources to WLOC services.
Manages a pool of resources from a VMware ESX Server resource pool. An ESX Agent does not need to run on a specific physical machine. It communicates with the VMware Virtual Center (hypervisor software that controls instances of ESX Server) to discover the capabilities of the resource pool. An ESX Agent allocates all of the resources that the ESX Server resource pool exposes for hosting services, regardless of the underlying physical implementation. For example, an ESX Agent can pool resources from multiple physical machines or it can split a single physical machine into multiple pools.
Each type of Agent communicates with the Controller to describe the following types of resources on the machines that it manages:
Number of CPUs.
Software that is available at specified mount points.
The manner in which an Agent describes its resource inventory depends on the type of Agent, as follows:
For a Plain Agent, you specify the available resources when you create the Agent. This information is stored in an XML document that you can modify at any time.
For an ESX Agent, the Agent communicates with VMware Virtual Center to discover the CPU capacity, memory availability, and number of CPUs. You specify the software mount points when you create the Agent. As in the plain Agent case, this information is stored in an XML document that you can modify at any time.
See also Configuring the Controller and Agents. For more information about WLS-VE and the VMware VirtualCenter and data center, see BEA WebLogic Server Virtual Edition (WLS-VE) 9.2 V1.1.
Steps to Configure and Manage Agents
You create new Agents using the WLOC Configuration Wizard, as described in Configuring the Controller and Agents. After you create an Agent, you can update its configuration, as described in the following sections. The process varies slightly based on whether you are defining a plain or ESX Agent.