[OASIS Issue Tracker] Commented: (MQTT-58) How many messages are received for overlapping subscriptions?

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    [ http://tools.oasis-open.org/issues/browse/MQTT-58?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=34210#action_34210 ] 

Nick O'Leary commented on MQTT-58:
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The client will receive the message ONCE.

As for the QoS, there are some options:
 1. some heuristic that identifies the most specific matching subscription (a/b being more specific than a/+ - but this gets very hard to define with combinations of wildcards)
 2. the highest qos of all matching subscriptions
 3. the lowest qos of all matching subscriptions
 4. the earliest subscription
 5. the most recent subscription

Having thought through the options, I think it should be the highest qos of all matching subscriptions. The client has asked for that highest level of service for some part of its application logic. We need to honour that level.

It would illustrative to hear what rules existing implementations apply.







> How many messages are received for overlapping subscriptions?
> -------------------------------------------------------------
>
>                 Key: MQTT-58
>                 URL: http://tools.oasis-open.org/issues/browse/MQTT-58
>             Project: OASIS Message Queuing Telemetry Transport (MQTT) TC
>          Issue Type: Improvement
>          Components: core
>            Reporter: Allan Stockdill-Mander 
>
> A client has subscribed to a/+ with QoS2 and a/b with QoS1. A message is published to a/b. Does the client receive one or two messages? If one which QoS would apply?

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