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 on the link connection. There may be multiple routes sharing the same link

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

Load-sharing across brokers