[OASIS Issue Tracker] (MQTT-260) Add a CONNACK code of 'Try Another Server'

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

    [ https://issues.oasis-open.org/browse/MQTT-260?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=63627#comment-63627 ] 

Konstantin Dotchkoff commented on MQTT-260:
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Comments on #1 and #2 above:
1. This is a valid concern. Maybe it should be handled as non-normative comment. Even with a single Server there are situations where the Client state might get out of sync. Also administrative actions on the Server might lead to inconsistent state between the Client and the Server. We might consider proposing a Client to start with a clean session after it's been redirected to another Server as a non-normative text. 
2. Proposal: use a URL syntax that is be defined in the spec along the lines of 
<protocol>://<host_name>[:<port>]
where <protocol> would be mqtt for MQTT endpoints.



> Add a CONNACK code of 'Try Another Server'
> ------------------------------------------
>
>                 Key: MQTT-260
>                 URL: https://issues.oasis-open.org/browse/MQTT-260
>             Project: OASIS Message Queuing Telemetry Transport (MQTT) TC
>          Issue Type: Improvement
>          Components: core
>    Affects Versions: 5
>            Reporter: Raphael Cohn
>            Assignee: Raphael Cohn
>            Priority: Critical
>
> If we add a CONNACK return code of 'Try Another Server', this makes it easier for over-loaded servers to tell clients to redirect. This works in conjunction with MQTT-259, which advocates the use of DNS SRV records.
> Indeed, if we also added server-originated DISCONNECT packets with this return code, we could get clients to cleanly migrate to another server when a server is shutdown for maintenance.
> Please note, I do not favour the server also reporting which new server to connect to. There in lies the route to madness, as it means the current server has to know the state of all the others. That's intimate knowledge.



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