THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
Introduction
Please note: Whereas broker federation was introduced in the M3 milestone release, the discussion in this document is based on the richer capabilities of federation in the M4 release.
This document presents broker federation for the administrative user. For design and developer information, please see Federation Design Note.
What Is Broker Federation?
The Qpid C++ messaging broker supports broker federation, a mechanism by which large messaging networks can be built using multiple brokers. Some scenarios in which federation is useful:
- Connecting disparate locations across a wide area network. In this case full connectivity across the enterprise can be achieved while keeping local message traffic isolated to a single location.
- Departmental brokers that have a policy which controls the flow of inter-departmental message traffic.
- Scaling of capacity for expensive broker operations. High-function exchanges like the XML exchange can be replicated to scale performance.
- Co-Resident brokers Some applications benefit from having a broker co-resident with the client. This is particularly true if the client produces data that must be delivered reliably but connectivity to the consumer(s) is non-reliable. In this case, a co-resident broker provides queueing and durablilty not available in the client alone.
- Bridging disjoint IP networks. Message brokers can be configured to allow message connectivity between networks where there is no IP connectivity. For example, an isolated, private IP network can have messaging connectivity to brokers in other outside IP networks.
The qpid-route Utility
The qpid-route command line utility is provided with the Qpid broker. This utility is used to configure federated networks of brokers and to view the status and topology of networks.
qpid-route accesses the managed brokers remotely. It does not need to be invoked from the same host on which the broker is running. If network connectivity permits, an entire enterprise can be configured from a single location.
In the following sections, federation concepts will be introduced and illustrated using qpid-route.
Links and Routes
Federation occurs when a link is established between two brokers and one or more routes are created within that link. A link is a transport level connection (tcp, rdma, ssl, etc.) initiated by one broker and accepted by another. The initiating broker assumes the role of client with regard to the connection. The accepting broker annotates the connection as being for federation but otherwise treats it as a normal client connection.
A route is associated with an AMQP session established 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
Exchange-to-Exchanges Routes
Queue-to-Exchange Routes
Pull vs. Push Routes
qpid-route Summary and Options
Example Scenarios
Using QPID to bridge disjoint IP networks
Full mesh topology
Multi-tiered topology
+-----+
| 5 |
+-----+
/ \
+-----+ +-----+
| 2 | | 6 |
+-----+ +-----+
/ | \ | \
+-----+ +-----+ +-----+ +-----+ +-----+
| 1 | | 3 | | 4 | | 7 | | 8 |
+-----+ +-----+ +-----+ +-----+ +-----+
This topology can be configured using the following script.
## ## Define URLs for the brokers ## broker1=localhost:10001 broker2=localhost:10002 broker3=localhost:10003 broker4=localhost:10004 broker5=localhost:10005 broker6=localhost:10006 broker7=localhost:10007 broker8=localhost:10008 ## ## Create Topic Exchanges ## qpid-config -a $broker1 add exchange topic fed.topic qpid-config -a $broker2 add exchange topic fed.topic qpid-config -a $broker3 add exchange topic fed.topic qpid-config -a $broker4 add exchange topic fed.topic qpid-config -a $broker5 add exchange topic fed.topic qpid-config -a $broker6 add exchange topic fed.topic qpid-config -a $broker7 add exchange topic fed.topic qpid-config -a $broker8 add exchange topic fed.topic ## ## Create Topic Routes ## qpid-route dynamic add $broker1 $broker2 fed.topic qpid-route dynamic add $broker2 $broker1 fed.topic qpid-route dynamic add $broker3 $broker2 fed.topic qpid-route dynamic add $broker2 $broker3 fed.topic qpid-route dynamic add $broker4 $broker2 fed.topic qpid-route dynamic add $broker2 $broker4 fed.topic qpid-route dynamic add $broker2 $broker5 fed.topic qpid-route dynamic add $broker5 $broker2 fed.topic qpid-route dynamic add $broker5 $broker6 fed.topic qpid-route dynamic add $broker6 $broker5 fed.topic qpid-route dynamic add $broker6 $broker7 fed.topic qpid-route dynamic add $broker7 $broker6 fed.topic qpid-route dynamic add $broker6 $broker8 fed.topic qpid-route dynamic add $broker8 $broker6 fed.topic