Fix recovery channel metrics that are sent with realTag without offset

[Peshka1502]

Proposed Changes

Scenario: consuming messages from RabbitMQ with the automatic recovery feature enabled and autoAck=false using com.rabbitmq.client.impl.StandardMetricsCollector as the metric collector.

After a channel recovery I observed a memory leak. Analizing the memory dump huge amount of longs were stored in the following variable:
com.rabbitmq.client.impl.AbstractMetricsCollector$connectionState$channelState$unackedMessageDeliveryTags

So after a channel recovery in the class com.rabbitmq.client.impl.recovery.RecoveryAwareChannelN the deliveryTag is reseted and a activeDeliveryTagOffset is stored. So the processing is done with the deliveryTag + activeDeliveryTagOffset and this tag is stored in unackedMessageDeliveryTags in the consumedMessage of AbstractMetricsCollector. But when sending the basicAck is done with the realTag (without the offset) so it removes a different deliveryTag from unackedMessageDeliveryTags.

The proposed solution is to call the AbstractMetricsCollector.basicAck method with the proper deliveryTag (with offset) in the RecoveryAwareChannelN class (same for basicNack and basicReject)

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• Bugfix (non-breaking change which fixes issue #NNNN)
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Further Comments

If you want to reproduce this issue:

1. Enable the autorecovery feature, and autoAck = false
2. Start consuming messages
3. Stop rabbit cluster
4. Start rabbit cluster and let channel recover
5. Continue consuming messages
6. Check that com.rabbitmq.client.impl.AbstractMetricsCollector$connectionState$channelState$unackedMessageDeliveryTags contains deliveryTags that have been already ack'ed.

Best regards,
Taras

[pivotal-issuemaster]

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[michaelklishin]

Thanks, this seems reasonable. Please sign the CLA and we will QA this.

[pivotal-issuemaster]

@Peshka1502 Thank you for signing the Contributor License Agreement!

[acogoluegnes]

@Peshka1502 I added a test to check the fix, thanks!

[Peshka1502]

@acogoluegnes Great, thank you! Can this fix also be applied for the 4.x series?

[acogoluegnes]

@Peshka1502 Yes, I'll apply the patch to 4.4.x and release a 4.4.2 RC soon after.