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https://issues.apache.org/jira/browse/IGNITE-19028?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17709650#comment-17709650
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Kirill Tkalenko commented on IGNITE-19028:
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Looks good.
> Implement safe-time propagation for meta-storage raft-group
> -----------------------------------------------------------
>
> Key: IGNITE-19028
> URL: https://issues.apache.org/jira/browse/IGNITE-19028
> Project: Ignite
> Issue Type: Improvement
> Reporter: Ivan Bessonov
> Assignee: Semyon Danilov
> Priority: Major
> Labels: ignite-3
> Time Spent: 2.5h
> Remaining Estimate: 0h
>
> For the future implementation of schema-synchronization, we need to have a
> hybrid-timestamp, associated with the meta-storage.
> Database schema changes are always associated with time, and proper place to
> store them would be a meta-storage.
> We don't have an "partition replica listener" that would have been a single
> source of truth when it comes to new "write" commands. In case of
> meta-storage, all nodes may create write commands. Assigning a time from the
> _hlc_ wouldn't work - there's a chance of having out-of order events, which
> is really, really bad.
> In other words, timestamps should come in order. Does this mean that
> meta-storage should also have its own replica listener? That's one
> possibility.
> Another possibility is to make leader into a timestamp-generator. This would
> lead to changes in JRaft code, but still, this may be the right way to go. It
> simply requires less changes to the code. We should just remember to adjust
> the clock on leader's re-election, so that time would be monotonic.
> By the way, if we go with the second option, it would also fit safe time
> propagation in partitions.
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