1.6.  Compare the Network Deployment (ND) cell model with the flexible management model.


Flexible management

This release introduces an optional administrative model that enables you to implement a more flexible, scalable, and asynchronous administrative topology. This new loosely-coupled model, called "flexible management", is built around autonomous nodes that maintain local control over their configuration. Servers on a node are locally managed by an "administrative agent" that can host the administrative logic for all servers on a node, reducing their footprint. A central "job manager" process provides a single interface from which you can asynchronously submit administrative tasks to a node or group of nodes. Because it does not rely on tightly-coupled, synchronous communication, flexible management can be advantageous in situations that push the limits of the cell model, including environments with very large numbers of nodes, or topologies that include high-latency, long-distance links. Keep in mind that this new model is an option, and the cell model is still available. Many environments will still find the cell model to be the most appropriate, since it provides many services, like high-availability, that applications might require.

Two new Java processes, the administrative agent, and the job manager work together to enable the "flexible management" administrative topology. The administrative agent is responsible for the administrative logic for all servers on a node. By consolidating the management logic for all servers on the node, administrative overhead is reduced, and there is a single point of administration. After a profile has been registered with an administrative agent, the administrative console runs on the administrative agent, and not the application server. An administrative agent can only manage local servers. Multiple nodes can be administered remotely using a job manager. The job manager provides its own console, and enables you to send management jobs to registered servers through the administrative agent. Note that individual nodes retain their autonomy, and can still be managed locally, even when registered with a job manager. A job manager can also send commands to a deployment manager, providing a way to administer multiple Network Deployment cells from a single interface. The administrative agent is available as a part of all WebSphere Application Server packages, while the job manager is only available with the Network Deployment offering.

Figure 1.8. Flexible management topology

Flexible management topology

The job manager communicates with either administrative agents or deployment managers. The flexible management components enable some scenarios, like very large server farms, or a single administrative interface for separate data centers, that are not easy to manage with the traditional cell model.

Job manager

A job manager is a component that provides management capabilities for multiple standalone application servers, administrative agents, and deployment managers. It brings enhanced multiple node installation options for your environment.

It is possible to encounter a senario where there might be multiple distributed environments, each managed by their own deployment manager. With multiple deployment managers, they must be administered individually and there is no way of coordinating management actions between the different distributed environments. Distributed environment administration performance is affected by low latency networks because file synchronization between the deployment manager and node agent are dependent on network communication.

The job manager can be used to administer multiple distributed environments as well as standalone servers. The job manager administers the environment asynchronously using the concept of jobs. Because jobs are submitted asynchronously, a low latency network is sufficient, which can be useful when the environment is distributed over distant geographical areas.

The job manager is available only with WebSphere Application Server Network Deployment and WebSphere Application Server for z/OS.

To administer a distributed environment, the deployment manager is registered with the job manager. To administer standalone servers, the nodes managed by the administrative agent are registered with the job manager. This relation between the job manager and the environments it can interact with is shown below:

Figure 1.9. High-level overview of a job manager architecture

High-level overview of a job manager architecture

The job manager administers the registered environments by submitting jobs that perform tasks, for example:

The job manager has a repository for its own configuration files, which are related to security, administration of job manager, configurations, and so on, however, it does not maintain a master repository the way a deployment manager does. Rather, the job manager allows the administrative agents and deployment managers to continue managing their environment as they would have had they not been registered with the job manager. The job manager simply provides another point of administration.

The job manager can administer multiple administrative agents and deployment managers. Conversely, each administrative agent and deployment manager can be registered with multiple job managers.

Flexible management

Flexible management is a concept introduced with WebSphere Application Server V7.0. With flexible management components like the administrative agent and the job manager, you can build advanced and large-scale topologies and manage single and multiple application server environments from a single point of control. This reduces management and maintenance complexity.

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