Filter
Top Products
TABLE1–1 Features Available forEach Prole (Continued)
Feature DeveloperProle ClusterProle
EnterpriseProle(not
availablewithSunGlassFish
CommunicationsServer)
Security Manager Disabled Enabled Enabled
HADB Notavailable Notavailable Available
Load balancing Notavailable Available Available
Nodeagents Not available Available Available
Cluster
A cluster is a named collection of server instances sharing the same set of applications,
resources, and conguration information. A server instance can belong to exactly one cluster. A
cluster facilitates server instance load-balancing through distribution of a load across multiple
machines. A cluster facilitates high availability through instance-level failover. From an
administrative perspective, a cluster represents a virtualized entity in which operations on a
cluster (e.g. deployment of an application) act on all instances that make up the cluster.
Horizontal scaling is achieved by adding Enterprise Server instances to a cluster, thereby
increasing the capacity of the system. It is possible to add Enterprise Server instances to a cluster
without disrupting service. The HTTP, RMI/IIOP, and JMS load balancing systems distribute
requests to healthy Enterprise Server instances in the cluster.
High Availability - Availability allows for failover protection of Enterprise Server instances in a
cluster. If one application server instance goes down, another Enterprise Server instance takes
over the sessions that were assigned to the unavailable server. Session information is stored
using the session replication feature or by using the high-availability database (HADB). HADB
supports the persistence of HTTP sessions and stateful session beans.
Node Agent
A lightweight agent (e.g. hosting a JMX runtime only) is required on each node in the domain
to facilitate remote lifecycle management of instances. Its primary purpose is to start, stop, and
create server instances as instructed by the DAS. The Node Agent also acts as a watchdog and
restarts failed processes. Like the DAS, the Node Agent should only be required for certain
administrative operations and should not be expected to be highly available. However, the Node
Agent is an “always on” component, and must be congured to be started by the native O/S
node bootstrap (e.g. Solaris/Linux inetd, or as a Windows service). A Node Agent is not
required for the DAS.
EnterpriseServerConcepts
SunGlassFishEnterpriseServer2.1AdministrationGuide • December200828