Re: [mosquitto-dev] Messages are removed from the retain store, if expir

[Roger Light <roger@xxxxxxxxxx>]

Hi,

It took me a while to find it, but in section "3.3.1.3 RETAIN" of the
spec it states:

"If the current retained message for a Topic expires, it is discarded
and there will be no retained message for that topic."

So I believe Mosquitto to be compliant, and that there is no
ambiguity. I'm sorry this doesn't match the behaviour you are hoping
for.

Regards,

Roger

On Fri, 30 Oct 2020 at 09:42, Schär, Beat <beat.schaer@xxxxxxxxxx> wrote:
>
> Hi MQTT people
>
>
>
> I published a message to mosquitto with the following properties set :
>
> RETAIN flag set
> Property « Message Expiry Interval » set to 30sec.
>
>
>
> Now I discovered  that after this 30sec the message is not only cleaned from the broker’s session state of those clients to which it hasn’t been able to transmit, but obviously also from the retain store of the broker, because if I connect with another client after this 30sec have expired, I don’t get the retained value any longer.
>
>
>
> Beeing quite sure, that this was an implementation error, I consulted the MQTT5 specification. Unfortunately the spec is not very precise about this issue, so the implementation decision which has been taken in the mosquitto broker is legitimate. But I ask myself, if it would make sense to make this behaviour in the broker configurable.
>
>
>
> What do you think about it ?
>
>
>
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