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From "Gary Tully (JIRA)" <>
Subject [jira] Resolved: (AMQ-2198) Allow suppression of duplicate queue subscriptions in a cyclic network topology
Date Tue, 07 Apr 2009 19:53:34 GMT


Gary Tully resolved AMQ-2198.

    Resolution: Fixed

resolved in r762925

Addition of suppressDuplicateQueueSubscriptions to network broker configuration. When true,
a duplicate subscription resulting from a second order advisory in a cyclic network will be
ignored. the result is that with a networkTTL > 1 a consumer will be replicated on each
broker but the resulting consumers will not be replicated. It is as if the networkTTL remains
1 for Consumer advisory messages.

> Allow suppression of duplicate queue subscriptions in a cyclic network topology
> -------------------------------------------------------------------------------
>                 Key: AMQ-2198
>                 URL:
>             Project: ActiveMQ
>          Issue Type: Improvement
>          Components: Broker
>    Affects Versions: 5.2.0
>            Reporter: Gary Tully
>            Assignee: Gary Tully
>             Fix For: 5.3.0
> in a cyclic network of brokers (where each broker knows about each other) it is possible
to have a cyclic graph and multiple routes across the network. this occurs because some brokers
pick up the second order advisories that arise from a broker responding to an advisory from
another broker. The result is that a consumer on one broker can manifest itself as multiple
consumers on brokers across the network. Network priority gives precedence to the shortest
route when it is configured. This enhancement would ensure that there is only one route for
a given destination and makes the network more deterministic and a little simpler. With small
numbers of brokers in the network, this is often what you want.
> When topics are involved, the duplication leads to duplicate messages so duplicates for
topics are suppressed by default on trunk and will be in 5.3. For queues, as the message goes
to just one consumer, there is no duplicate issue, just some indeterminism in how a message
is routed through the network. This indeterminism is a means of fault tolerance and can be
a good thing so this feature is enabled via configuration for queues.
> see some more background on the topic case @

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