Build-up of unwanted messages
-----------------------------
Key: AMQ-3004
URL: https://issues.apache.org/activemq/browse/AMQ-3004
Project: ActiveMQ
Issue Type: Bug
Affects Versions: 5.4.1
Reporter: Roelof Naude
One of our installations have several consumers. These consumers subscribe for
messages from a queue linked to a virtual topic. All consumers supply a
selector. Some consumers connect, process any persisted messages, then
disconnect. These connect/disconnect cycles are repeated a few times a day.
What we've seen is that messages build-up for consumers. These messages does
not match the supplied selector. The side effect of this was that we ran into a
situation whereby message "got stuck". Increasing the _maxPageSize_ property
helped. This is unfortunately a short term solution.
A simple test was constructed whereby *selectorAware* was set to *true*:
{code:xml}
<virtualDestinations>
<virtualTopic name="VirtualTopic.>" prefix="Consumer.*."
selectorAware="true"/>
</virtualDestinations>
{code}
What we noticed is that:
# Messages are correctly received by a connected consumer
# A consumer that connects, disconnects and re-connects later will loose any
messages that were send in the time period it was disconnected.
This behaviour was unexpected. From the AMQ documention
(http://activemq.apache.org/virtual-destinations.html):
{quote}
>From version 5.4, dispatch from virtual topics to subscription queues can be
>selectorAware such that only messages that match one of the existing
>subscribers are actually dispatched. Using this option prevents the build up
>of unmatched messages when selectors are used by exclusive consumers
{quote}
Note: it does not state that the consumer needs to be connected for this
feature to work.
Given the test it looks like subscriptions itself are not persisted, thus the
AMQ broker has no idea that it should enqueue a message for a particular
subscription queue.
Would it be possible to add either of:
# Persist subscription detail, specifically for the case where the
subscription's selector should be applied to the subscription queue
# Propagate selectors and the attached subscription queue to the top-level
virtual topic so that only interested messages can be delivered to the intended
recipient?
Anything else we can try, supply or help with?
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