AS 7 core concepts

Now that we have downloaded and installed JBoss AS 7, it is worth familiarizing ourselves with some basic concepts. Initially, JBoss AS 7 can be run in two modes: the standalone mode and the domain mode.

In the standalone mode, each JBoss Application Server 7 instance is an independent process (similar to the previous JBoss AS versions, such as Version 4, Version 5, or Version 6). The standalone configuration files are located under the standalone/configuration of the application server.

In the domain mode, you can run multiple application servers and manage them from a central point. A domain can span multiple physical (or virtual) machines. On each machine we can install several instances of JBoss Application Server 7, that are under the control of a Host Controller process. The configuration files in the domain mode are located under the domain/configuration folder of the application server.

From the process point of view, a domain is made up of three elements:

Additionally, when starting a domain, you will see another JVM process running on your machine: this is the Process Controller. It is a very lightweight process whose primary function is to spawn server processes and Host Controller processes, and manage their input/output streams. Since it is not configurable, we will not discuss it any further.

The following diagram depicts a typical domain deployment configuration:

As you can see from the preceding screenshot, one host (Host1) acts as a dedicated domain controller. This is a common best practice adopted in domain-managed servers in order to logically and physically separate the administration unit from the servers where the applications are hosted.

The other hosts (Host2 and Host3) contain the domain application servers, which are divided into two server groups: main-server-group and other-server-group . A server group is a logical set of server instances that will be managed and configured as one. Each server group can in turn be configured with different profiles and deployments; for example, in the preceding domain you can provide some services with server-group-one and other services with other-server-group.

Going into the details of the domain configuration is beyond the scope of this book; however, by the end of this chapter we will show how to deploy application units in a domain using the Command Line Interface available in AS 7.