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https://issues.apache.org/jira/browse/AMQ-2711?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14233163#comment-14233163
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Tim Bain commented on AMQ-2711:
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If you force `conduitSubscriptions=true` for topics, you lose the ability to
ensure that only messages that actually have a consumer on broker A will be
forwarded from broker B, which could be important if there's a
bandwidth-limited link between the two.
With `conduitSubscriptions=true`, selectors are ignored and *all* messages are
passed from B to A, even if all consumers on A have selectors that will exclude
the message. In certain scenarios the duplicate messages that could result
from setting `conduitSubscriptions=false` would be better than the use of
limited bandwidth to pass messages that will be immediately discarded on broker
A. And it's not "almost inevitable" that `conduitSubscriptions=false` will
case problems; you won't get duplicate messages if all consumers have unique
selectors such that a message is only ever delivered to a singe consumer.
Allowing both values of `conduitSubscriptions` for both destination types
doesn't hurt anything and it gives configuration options that are useful in
certain situations, so let's close this as Won't Fix.
> conduitSubscriptions flag on networkConnector element should only affect
> queues, not topics
> -------------------------------------------------------------------------------------------
>
> Key: AMQ-2711
> URL: https://issues.apache.org/jira/browse/AMQ-2711
> Project: ActiveMQ
> Issue Type: Improvement
> Components: Connector
> Affects Versions: 5.3.1
> Reporter: Fintan Bolton
> Fix For: 5.x
>
>
> In the doc for 'Networks of Brokers',
> http://activemq.apache.org/networks-of-brokers.html, it says that it is
> sometimes useful to disable {{conduitSubscriptions}} for queues, because this
> gives you a better load balancing effect when consumers are attached to
> various points in the broker network. The only trouble is, currently it does
> not seem practical to disable {{conduitSubscriptions}}, because this almost
> inevitably causes trouble with topics. That is, it can easily happen that
> topic messages are duplicated, if {{conduitSubscriptions}} is set to
> {{false}}.
> It seems like it would be better if topic subscriptions where *always*
> treated as conduits and the {{conduitSubscriptions}} attribute only affected
> queue subscriptions. That way, you could happily disable conduits for queues
> while leaving it enabled for topics.
> A bit of investigation is probably needed, however, to make sure that there
> aren't any edge cases where you might actually want to disable conduit
> subscriptions for topics.
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