Get improved high availability and horizontal scalability with the enhanced clustering capabilities of GlassFish Version 2. Learn how the latest version of this open source application server's flexible clustering architecture provides ease of use and high administrative control to enhance your experience and facilitate these aspects for you.

"Clusters in an application server enhance scalability and availability," notes a recent SDN article. "In order to support the goals of scalability and high availability, the GlassFish application server provides the following server-side entities:

• Server Instance: A server instance is the Java EE server process (the GlassFish application server) that hosts your Java EE applications. As required by the Java EE specification, each server instance is configured for the various subsystems that it is expected to run.
• Node Agent: A node agent is an agent process that runs on every physical host where a server instance runs. The node agent manages the life cycle of a server instance when directed by the Domain Administration Server (DAS)....
• Cluster: A cluster is a logical entity that determines the configuration of the server instances that make up the cluster. Usually, the configuration of a cluster implies that all the server instances within the cluster have homogeneous configuration. An administrator typically views the cluster as a single entity and uses the GlassFish Admin Console or a command-line interface (CLI) to manage the server instances in the cluster."

These features along with GlassFish's flexible clustering architecture that consists of administrative domains, domain administrative servers and physical machines, add up to:

• "High availability: Multiple server instances, capable of sharing state, minimize single points of failure, particularly when combined with load balancing schemes. In-memory replication of server session data minimizes disruption for users when a server instance fails.
• Horizontal scalability: As user load increases, additional machines, server instances, and clusters can be added and easily configured to handle the increasing load. GMS (Group Management Service) eases the administrative burden of maintaining a high-availability cluster."

Two typical failover requests from a load balancer are presented to show how the GlassFish application server requires no special information in order to perform well when a failure occurs.

For details on the described clustering capabilities and to learn how to get started in deploying your application to a GlassFish cluster, see Kedar Mhaswade, Prashanth Abbagani and Rick Palkovic's article Clustering in GlassFish Version 2. [...read more...]

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