[OASIS Issue Tracker] (MQTT-504) No way to tell when a retained message was set

[OASIS Issues Tracker <workgroup_mailer@lists.oasis-open.org>]

    [ https://issues.oasis-open.org/browse/MQTT-504?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=67505#comment-67505 ] 

Ken Borgendale commented on MQTT-504:
-------------------------------------

One more option (call it 1a).  If  the receiver of the message knows the publication expiry with which the message was sent, the delta publication expiry tells the receiver how long it is since the retained message was sent.  This is a mechanism widely used in TCP to determine the hop count by looking at the TTL. This has the advantage that there is no change to any existing spec or code.  At most we could point this out in a non-normative comment.

> No way to tell when a retained message was set 
> -----------------------------------------------
>
>                 Key: MQTT-504
>                 URL: https://issues.oasis-open.org/browse/MQTT-504
>             Project: OASIS Message Queuing Telemetry Transport (MQTT) TC
>          Issue Type: New Feature
>          Components: core
>    Affects Versions: 5, CSD01
>            Reporter: Ian Craggs
>            Priority: Minor
>
> I implemented this feature in a broker specific way myself some years back, so I know it's useful.  It was raised on Twitter to me here: https://twitter.com/MichMich/status/903283262415568898
> Maybe expiry would be enough for some use cases.
> We could allow the server to set a property with the received timestamp on the retained message.



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