Virtual Hosts

A virtual host represents a service that acts as a host for other services.

Virtual Host Characteristics

• Multiple virtual hosts can exist on a single physical server.

• Every virtual host has a parent host, which can be either a physical host or another virtual host.

• Virtual hosts can be nested arbitrarily, although the outermost parent host must be a physical host.

• You can run comparisons against virtual hosts.

• In most cases, virtual hosts will be created as a by-product of installing plug-in related components.

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  Note –

  To determine if a component will create a host, view the component's Details page. If the Creates Host field has a location listed, the component will create a host at that location upon component installation.

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Virtual hosts represent logical deployment targets. For example, a WebLogic virtual host can represent a WebLogic application server as a deployment target.

The virtual host provides an interface between the component being deployed (in this example, the web application) and the component being targeted (in this example, the application server).

Rather than deploy web applications directly to WebLogic, which would entail working with the application server's custom administrative console on each host, by using the virtual hosts within the provisioning system, you can deploy a web application to the virtual host and the virtual host will provide WebLogic with specific configuration information. This functionality is particularly useful if you need to deploy a web application to several hosts at once.

The following list includes examples of information supplied to a virtual host and used in the interaction between a virtual host and the service running on a remote machine.

• user name and password for the service

• port numbers

• connection types

By using the provisioning system rather than performing deployments manually, you can receive the following benefits.

• Simultaneous deployments to all hosts in a host set.

• Version control that tracks all deployment and configuration data for reference, reconstruction, and automated rollback to previous states.

• Logging and reporting that creates detailed logs of every action taken by the system across all applications and managed servers. These logs provide a complete audit history of every change made to every host.

• Differential deployments that enable delta-only distribution of large content directories, thereby speeding up deployments significantly and optimizing incremental directory updates.

Virtual hosts are also useful for maintaining multiple instances of an application on a single physical host. These hosts establish a clear distinction between physical servers and the applications running on them. This distinction is especially useful when managing multiple applications that must interact with one another to function.

Because each virtual host represents a specific service, do not attempt to migrate a virtual host definition to another server. For example, if you need to migrate your WebLogic application server to a new physical host, migrate the application and create a new virtual host. If you attempt to migrate the virtual host to a different physical host, the Master Server will contain records with inaccurate information about the migrated application server.

Targetable Components

Hosts can be created manually or they can be created by a special type of component, the targetable component. Targetable components are available with many of the third-party plug-ins.

The targetable component represents a service that components and plans need to use as an installation or call target. When a targetable component is installed, the component creates the virtual or physical host, which acts as the interface between the targetable component and the other components and plans.

When the targetable component is installed, the host is created with a predefined set of information. This information set includes the following values.

• Host name

• Host type with default values

  This host type is included with the plug-in.

• Type of host: physical or virtual

• The ID of the targetable component that created the host

After the targetable component creates the host, you can modify the host's description and host-type attributes.

If a new version of the targetable component is installed, the targetable component's host is updated with the new targetable component information.

When the targetable component is uninstalled, the host that it created is also deleted.