WildFly 8 core concepts
Now that we have downloaded and installed WildFly 8, it is worth spending a few minutes
familiarizing ourselves with some basic concepts. The architecture and most of the core
ideas are taken straight from JBoss AS 7; although, there are some new mechanisms that
were introduced with the newest version (for example, role-based security for the manage-
ment system, reduced number of used ports, and a new patching system). Just like JBoss
AS 7, WildFly can be run in two modes: the standalone mode and domain mode.
In the standalone mode, each WildFly instance is an independent process (similar to the
previous JBoss AS versions, such as Version 4, Version 5, Version 6, and the standalone
mode in Version 7). The standalone configuration files are located under the stan-
dalone / configuration directory 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 WildFly that are under the control of a Host Controller
process. The configuration files in the domain mode are located under the domain / con-
figuration folder of the application server.
From the process point of view, a domain is made up of three elements:
• Domain Controller : The domain controller is the management control point of
your domain. A WildFly instance running in the domain mode will have at the
most one process instance acting as a domain controller. The domain controller
holds a centralized configuration, which is shared by the node instances that be-
long to that domain.
• Host Controller : This is the process that is responsible for coordinating the life
cycle of server processes and the distribution of deployments from the domain con-
troller to the server instances.
• Application server nodes : These are regular Java processes that map instances of
the application server. Each server node, in turn, belongs to a server group. Do-
main groups are explained in detail when we will discuss the domain configuration
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 in-
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