Dhiraj Bokde created AMQ-5092:
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Summary: MQTT uses duplicate packet IDs for PUBLISH messages
Key: AMQ-5092
URL: https://issues.apache.org/jira/browse/AMQ-5092
Project: ActiveMQ
Issue Type: Bug
Components: MQTT
Affects Versions: 5.9.0
Reporter: Dhiraj Bokde
Fix For: 5.10.0
MQTT protocol converters does not correctly generate unique packet ids for
retained and non-retained publish messages sent to clients. MQTT requires that
all Publish messages with QoS > 0 must have a unique packet id which can be
used by clients to coordinate the PUBACK, PUBREC, PUBREL and PUBCOMP messages
depending upon the QoS flow.
Although retained messages published on creation of client subscriptions are
copies of retained messages, they must carry a unique packet id when dispatched
to clients. ActiveMQ re-uses the retained message's packet id, which makes it
difficult to acknowledge these messages when wildcard topics are used.
ActiveMQ also sends the same non-retained message multiple times for every
matching subscription for overlapping subscriptions. These messages also re-use
the publisher's message id as the packet id, which breaks client
acknowledgment.
A patch is included, which fixes all the above scenarios. It generates a unique
packet id for every publish (retained and non-retained), and also ensures that
redelivery on the same connection will re-use message ids, with the dup flag
set. The patch also maps JMS redelivery status for a subscription to the MQTT
Dup flag to indicate duplicate messages. Unit tests are included to test
correct packet id generation.
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