onlyMIT commented on issue #2466: ARTEMIS-2206 The MQTT consumer reconnection caused the queue to not be cle… URL: https://github.com/apache/activemq-artemis/pull/2466#issuecomment-453845902 @jbertram I have a question to consult you and hope you can answer it. 1. Why is there MULTICAST and ANYCAST routing types for Artemis subscriptions to MQTT.I think there should be only MULTICAST routing type in the MQTT protocol. Perhaps the purpose of this design is to enable Artemis' MQTT implementation to support both publish/subscribe and shared consumption functions.But it doesn't seem to support that.But it doesn't like to support this feature. Two consumers using the same clientId, defining the same topic on separate nodes, produce ANYCAST addresses(as `org.apache.activemq.artemis.tests.integration.mqtt.imported.MqttClusterRemoteSubscribeTest`).However, two consumers using the same clientId subscribe to the same address in the same node, and the latter consumer connection will cause the former consumer connection to be forcibly closed, and no ANYCAST address will be generated. Even these are not problems. But this will export when using different keys(use addressName as key or use "clientId+'.'+addressName" as key) to store the binding, we can't make sure that all calls to the `locateQueue(SimpleString queueName)` method take this into account(as in `addSubscription` method,only use "clientId+'.'+addressName" as key to call `locateQueue(SimpleString queueName)` .I think most people are not aware of this detail when calling the locateQueue(SimpleString queueName) method or even if it is easy to be ignored, it is very unsafe. I hope you can help me identify the problem so that I can determine how to solve it.
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