WAS v8.5 > WebSphere applications > Service integration > Bus destinations

Foreign destinations and alias destinations

Foreign destinations and alias destinations are types of bus destination. A foreign destination represents a destination defined in another bus (a foreign bus). An alias destination maps to an alternative name for a bus destination defined either in the local bus or in a foreign bus.

Usually, we do not need to configure a foreign destination or an alias destination:

You use a foreign destination when we need to override messaging defaults, security settings, or both for an individual destination on a foreign bus. You define a foreign destination on the local bus. When an application that is connected to the local bus sends messages to the destination in the foreign bus, the attributes of the foreign destination override the destination default values. We can set properties and destination roles, but we cannot map to an alternative name for the destination.

You use an alias destination when we need to use an alternative name for a bus destination. The bus destination can be on the local bus or on a foreign bus. You configure an alias destination on the local bus. When an application in the local bus uses the alias destination, the specified bus name and destination name are mapped to a new name. If we use an alias destination, we can also set properties, destination roles, or both.

When an application that is connected to a bus specifies a destination name and bus name in its JMS destination object (queue or topic) that match the identifier and bus of an alias destination defined in that bus, the destination the application accesses is the same as if the application specified the target identifier and target bus from the alias destination. We can also use a alias destination defined in a foreign bus if you need to redirect messages that arrive over a foreign bus connection to differently named destinations or buses, and we cannot modify the configuration of the source bus.


Foreign destinations

A foreign destination represents a destination defined in another bus (a foreign bus). We can use a foreign destination for point-to-point messaging. You use a foreign destination if you need to override security settings, or messaging defaults, for an individual destination on a foreign bus. The foreign bus can be another service integration bus or a WebSphere MQ network (that is, one or more interconnected WebSphere MQ queue managers or queue-sharing groups).

To override messaging defaults of a destination on a foreign bus, you configure the properties (for example, the default priority) of the foreign destination. To override security settings and control which users and groups in the local bus have access to a destination in a foreign bus, you configure the destination roles of the foreign destination. These properties apply when an application that is connected to the local bus sends messages to the destination in the foreign bus.

When you define a foreign destination, use the actual names of the foreign bus and the destination on the foreign bus, so the JMS destination object does not change.

When an application that is connected to the local bus sends messages to the destination in the foreign bus, service integration in the local bus uses the properties and destination roles of the foreign destination, rather than the default values from the definition of the foreign bus (on the local bus).

Typically, you configure the properties of a foreign destination to match the properties configured for that destination in the foreign bus (where that destination is a local destination), but this is not essential.

We can also configure destination roles for the foreign destination. Service integration in the local bus uses these roles to control which users and groups in the local bus have access to the destination. It also complements any access controls the foreign bus applies.

We do not use foreign destinations for publish-subscribe messaging. Instead, applications publish messages locally using a topic space destination in the local bus, and you configure a service integration bus link or a WebSphere MQ link. These links propagate the published messages into the foreign bus, or buses, where subscribers receive the messages. For a link to a service integration bus, configure topic space mappings, as described in Configure topic space mappings between service integration buses. For a link to a WebSphere MQ network, configure a publish/subscribe bridge, as described in Publish/subscribe messaging through a WebSphere MQ link.

Service integration cannot use configuration information that is scoped to a foreign bus. If an appropriate foreign destination is not defined on the local bus, service integration uses default values for the destination attributes.

Figure 1 shows a JMS application that sends messages from the local bus, Bus 1, to a destination in a foreign bus, Bus 2. Bus 1 has a foreign bus connection defined, which it uses to forward the message to the foreign bus. The foreign destination is not defined in the local bus. Bus 1 gets the destination defaults from the foreign bus connection.

Figure 1. Point-to-point messaging between two buses with no foreign destination configured

Figure 2 shows a JMS application that sends messages from the local bus, Bus 1, to a destination in a foreign bus, Bus 2. Bus 1 has a foreign bus connection defined, which it uses to forward the message to the foreign bus. Bus 1 includes a foreign destination definition. Bus 1 gets the destination defaults from the foreign destination.

Figure 2. Point-to-point messaging between two buses with a foreign destination configured on the local bus


Alias destinations

An alias destination maps an alternative name for a bus destination. We can use an alias destination for point-to-point messaging or publish/subscribe messaging. An alias destination maps a bus name and destination name (identifier) to a target where the bus name, or the destination name, or both, are different. An alias destination can map to a queue destination or a topic space destination. If required, alias destinations can be chained so the target destination is itself an alias destination.

You use an alias destination when we need to make a destination available under an alternative name. For example:

When we use an alias destination, we can also set properties (for example, the default quality of service) for the alias destination. When an application uses the alias destination, these properties override the properties of the target destination. If we do not want to override a property, configure the alias destination to inherit the corresponding property from the target destination.

When we use an alias destination, we can also configure destination roles for the alias destination. When the application uses the alias destination, service integration in the local bus uses these roles to control which users and groups in the local bus have access to the target destination. If we do not want to override the security for the target destination, configure the alias destination to delegate the authorization check to the target destination.

Figure 3 shows a JMS application that sends messages from the local bus, Bus 1, to a destination in a foreign bus, Bus 2. Bus 1 has a foreign bus connection defined, which it uses to forward the message to the foreign bus. The JMS destination does not point to the target queue, but points to Bus X, Queue Y. Bus 1 includes an alias destination that maps Bus X, Queue Y to the target destination Bus 2, Queue 2. Bus 1 gets the destination defaults from the alias destination.

Figure 3. Point-to-point messaging between two buses with an alias destination configured on the local bus


Use an alias destination for a destination in a foreign bus

If an application uses an alias destination to access a destination defined in a foreign bus, we can configure the alias destination with the specific properties, destination roles, or both the application requires. This means that you probably do not need to define a foreign destination as well.


Related concepts:

Configurations that include WebSphere MQ
Interconnected bus configurations
Destination security
Point-to-point messaging across multiple buses


Related


Create an alias destination on a bus
Configure alias destination properties
Create a foreign destination on a bus


Reference:

Map destinations to and from WebSphere MQ queues, topics, and destinations
WebSphere MQ naming restrictions


Related information:

Alias destination [Settings]
Foreign destination [Settings]


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