1.9. About Server Groups
A server group is a collection of server instances that are managed and configured as one. In a managed domain, every application server instance belongs to a server group, even if it is the only member. The server instances in a group share the same profile configuration and deployed content.
A domain controller and a host controller enforce the standard configuration on all server instances of every server group in its domain.
A domain can consist of multiple server groups. Different server groups can be configured with different profiles and deployments. A domain can be configured with different server tiers providing different services, for example.
Different server groups can also have the same profile and deployments. This can, for example, allow for rolling application upgrades where the application is upgraded on one server group and then updated on a second server group, avoiding a complete service outage.
The following is an example of a server group definition:
Example 1.2. Server group definition
<server-group name="main-server-group" profile="default"> <socket-binding-group ref="standard-sockets"/> <deployments> <deployment name="foo.war_v1" runtime-name="foo.war"/> <deployment name="bar.ear" runtime-name="bar.ear"/> </deployments> </server-group>
A server group includes the following mandatory attributes:
A server group includes the following optional attributes:
- name: the server group name.
- profile: the server group profile name.
- socket-binding-group: the default socket binding group used for servers in the group. This name can be overridden on a per-server basis in
host.xml. However, this is a mandatory element for every server group and the domain can not start if it is missing.
- deployments: the deployment content to be deployed on the servers in the group.
- system-properties: the system properties to be set on servers in the group
- jvm: the default JVM settings for all servers in the group. The host controller merges these settings with any other configuration provided in
host.xmlto derive the settings used to launch the server's JVM.
- socket-binding-port-offset: the default offset to be added to the port values given by the socket binding group.
- management-subsystem-endpoint: set to
trueto have servers belonging to the server group connect back to the host controller using the endpoint from their Remoting subsystem (the Remoting subsystem must be present for this to work).