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A route is associated with an AMQP session established on over the link connection. There may be multiple routes sharing the same link. A route controls the flow of messages across the link between brokers. Routes always consist of a session and a subscription for consuming messages. Depending on the configuration, a route may have a private queue on the source broker with a binding to an exchange on that broker.

Routes are unidirectional. A single route provides for the flow of messages in one direction across a link. If bidirectional connectivity is required (and it almost always is), then a pair of routes must be created, one for each direction of message flow.

The qpid-route utility allows the administrator to configure and manage links and routes separately. However, when a route is created and a link does not already exist, qpid-route will automatically create the link. It is typically not necessary to create a link by itself. It is, however, useful to get a list of links and their connection status from a broker:

$ qpid-route link list localhost:10001

Host            Port    Transport Durable  State             Last Error
=============================================================================
localhost       10002      tcp       N     Operational       
localhost       10003      tcp       N     Operational       
localhost       10009      tcp       N     Waiting           Connection refused

The example above shows a link list query to the broker at "localhost:10001". In the example, this broker has three links to other brokers. Two are operational and the third is waiting to connect because there is not currently a broker listening at that address.

The Life Cycle of a Link

When a link is created on a broker, that broker attempts to establish a transport-level connection to the peer broker. If it fails to connect, it retries the connection at an increasing time interval. If the connection fails due to authentication failure, it will not continue to retry as administrative intervention is needed to fix the problem.

If an operational link is disconnected, the initiating broker will attempt to re-establish the connection with the same interval back-off.

Dynamic Routing

Static Routing

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