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https://issues.apache.org/jira/browse/QPID-2418?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12851830#action_12851830
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Robbie Gemmell commented on QPID-2418:
--------------------------------------
On line 1086 (after patching) this code segment needs updated:
if (_subscriptionTopics.containsKey(name) &&
_subscriptionSelectors.containsKey(name))
{
if (!_subscriptionTopics.get(name).equals(topic) ||
!_subscriptionSelectors.get(name).equals(messageSelector))
{
_logger.info("Unsubscribing from topic " + topic + " with
subscription exchange " + name
+ " and selector " + messageSelector);
unsubscribe(name);
}
}
If the subscription name has been seen before but used without a selector, then
in the outer if statement the first test will success but the second will fail,
causing the inner if statement to detect subscription change not to be
evaluated. However, if the new subscription with reused name happens to be
adding a selector then this should be classified as a selector change (from no
selector) and cause unsubscription before proceeding.
Also, there is possibility of deadlock when creation of a new durable
subscriber occurs with the same subscription name as an existing open
subscriber, which will cause unsubscribe+closure of the old subscriber. The
create method will hold the new lock added, but closing the subscription will
contact the broker, which will reply and then a different thread will execute
the returned BasicCancelOK method and try to aquire the lock in
deregisterConsumer() in order to complete the closure, causing the first thread
executing the close to timeout and throw an exception. Looking at the map
usages it seems there is actually no need to acquire the same lock in
deregisterConsumer(), only a need to govern access to the subscriptions and
reverseSubscriptionMaps, which could be achieved using a second lock that
doesnt encompass the subscriber.close() operation.
> Existing durable subscription with selector is not unsubscribed during
> change to new subscription
> --------------------------------------------------------------------------------------------------
>
> Key: QPID-2418
> URL: https://issues.apache.org/jira/browse/QPID-2418
> Project: Qpid
> Issue Type: Bug
> Components: Java Client
> Affects Versions: M4, 0.5, 0.6
> Reporter: Robbie Gemmell
> Assignee: Robbie Gemmell
> Fix For: 0.7
>
> Attachments: 0001-QPID-2418-branch.patch, 0001-QPID-2418-trunk.patch
>
>
> AMQSession.createDurableSubscriber(topic, name, messageSelector, noLocal)
> does not unsubscribe existing durable subscriptions. Whilst it does check for
> existing durable subscriptions in use by the client with the same name, it
> instead simply closes the subscriptions then creates a new one. As a result
> of not unsubscribing, the queue backing the subscription is not deleted
> before being used by the updated subscription as it should be (and as happens
> in the 0_8 and 0_10 subclasses when using durable subscriptions without
> selectors).
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