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From "Miroslav Novak (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ARTEMIS-679) Activate most up to date server from master-slave(live-backup) pair
Date Thu, 11 Aug 2016 12:18:20 GMT

    [ https://issues.apache.org/jira/browse/ARTEMIS-679?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15417112#comment-15417112
] 

Miroslav Novak commented on ARTEMIS-679:
----------------------------------------

In replicated journal when backup is started before live, it does not activate. It waits for
live server to start first. Problem is that live always activates. No matter whether backup
had up-to-date journal or not. This feature would be about exchanging last timestamps of write
changes on Artemis journal between live and backup. Server with latest time stamp would activate.
Server with older timestamp would restart.

Great benefit of this approach is that no matter which server from live-backup pair is started
first. Server with most up-to-date journal will always start. 

> Activate most up to date server from master-slave(live-backup) pair
> -------------------------------------------------------------------
>
>                 Key: ARTEMIS-679
>                 URL: https://issues.apache.org/jira/browse/ARTEMIS-679
>             Project: ActiveMQ Artemis
>          Issue Type: New Feature
>          Components: Broker
>    Affects Versions: 1.3.0
>            Reporter: Miroslav Novak
>            Priority: Critical
>
> if there are 2 live/backup pairs with replicated journal in colocated topology Artemis1(L1/B2)
<-> Artemis2(L2/B1) then there is no easy way to start them if they're all shutdown.
> Problem is that there is no way how to start the servers with most up-to-date journal.
If administrator shutdown servers in sequence Artemis1 and then Artemis 2. Then Artemis 2
has the most up-to-date journals because backup B1 on server2 activated.
> Then If administrator decides to start Artemis2 then live L2 activates and backup B1
waits for live L1 in Artemis 1 to start. But once L1 starts then L1 replicates its own "old"
journal to B1.
> So L1 started with bad old journal. I would suggest that L1 and B1 compares theirs journals
and figure out which one is more up-to-date. Then server with more up-to-date journal activates.
> In scenario described above it would be backup B1 which will activate first. Live L1
will synchronize its own journal from B1 and then failback happens. 



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