Re: [mosquitto-dev] PUBACK sent after disconnect on publish

[Mikkel Kirkgaard Nielsen <miki@xxxxxxxxx>]

On February 22nd 2020 01.43.36 CET, Greg Troxel <gdt@xxxxxxxxxx> wrote:
>Perfectly fair, but it seems to me that the broker not publishing
>something because of a write error on puback is not right.  Maybe I am
>off base w.r.t. to the spec and that is intended, though.

A quick read seems to indicate that this behaviour is according to the specification.The 3.1.1 spec. ch. 4.3.2[1] about QoS 1 says (non normative) that delivery (relay to subscribers) is not required before SUBACK.

The ownership of the message, however, is first transferred to the receiver (broker) when the sender (publishing client) receives the PUBACK. So a strict interpretation could be to refrain from relaying to subscribing clients before the successful PUBACK.

[1] http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Toc398718101
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Mikkel