[OASIS Issue Tracker] Commented: (MQTT-16) Reserve $SYS topic name

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

    [ http://tools.oasis-open.org/issues/browse/MQTT-16?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=33532#action_33532 ] 

Alex Kritikos commented on MQTT-16:
-----------------------------------

Hi Dave,

i dont believe $SYS is mentioned anywhere in the specification. Sure some servers use it and some are not, so including semantics for it in the specification may be suitable for some vendors (as they have to do nothing) and unsuitable for others (as they need to implement it). 

I do not disagree that management / monitoring are important  and dont mind starting the discussion now, but typically we would need to standardise the base protocol first and then provide a separate specification which may be the result of a dedicated TC.

I expect this to be a lengthy discussion, perhaps we could indicate that topics starting with $ (or other character) are special, how special and what are the capabilities needs to be specified in a generic enough way so that different vendors can innovate offering unique capabilities in a neutral way so that it can be done with any compliant MQTT client.

Thanks,

Alex Kritikos
Software AG

> Reserve $SYS topic name
> -----------------------
>
>                 Key: MQTT-16
>                 URL: http://tools.oasis-open.org/issues/browse/MQTT-16
>             Project: OASIS Message Queuing Telemetry Transport (MQTT) TC
>          Issue Type: Improvement
>          Components: core
>    Affects Versions: 3.1.1
>            Reporter: David Locke
>             Fix For: 3.1.1
>
>
> Many MQTT implementations today use $SYS as the head of a topic string for use in administration  (configuration, operations, monitoring).   
> Can the $SYS or a similar topic name be reserved for future use ?   As $SYS is already used by a number of servers using a different top level topic would avoid conflicts. 
> Would be good to collect ideas for a $SYS topic space.  These ideas could initially go into a non-normative document but with potential for inclusion in a future spec.  The intent being servers can implement  some aspects of administration and monitoring in a consistent way
> Some examples:
> - Admin action like "unretain" a retained topic   e.g. $SYS/topic/unretain    (payload is the topic to unretain)
> - Client wishes to query what subscriptions it has made    e.g. $SYS/client/getsubs  (topic is clientid)
> - Client wishes to query how many messages are queued up awaiting delivery e.g. $SYS/client/getNoQueuedMessages  
> - Query the  state of the MQTT server e.g. $SYS/server/getStatus 
> These examples should not be taken literally they are purely to show the type of things a $SYS topic space could be used for.

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