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https://issues.apache.org/jira/browse/CASSANDRA-19448?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17829886#comment-17829886
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Tiago L. Alves commented on CASSANDRA-19448:
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[~maxwellguo] I've looked into the code and it seems to be possible to
implement millisecond and microsecond-level PIT restore. Supporting millisecond
requires changes in `CommitLogArchiver` only while supporting microsecond
requires additional changes in `CommitLogReplayer`.
In both `CommitLogArchiver` and `CommitLogReplayer`, `restorePointInTime` and
`restoreTarget` respectively, we're assuming long values in milliseconds.
Supporting millisecond level PIT restore, can be achieved by just recognizing
the milliseconds part specified in `restore_point_in_time` configuration. The
existent code does not fail parsing if milliseconds are specified but it will
ignore it.
To support microsecond granularity, we need further changes in
`CommitLogReplayer` to accept microseconds instead of forcing comparison to be
in milliseconds.
I have a patch that adds support for millisecond-level PIT restore and issues
warnings on attempts to specify microseconds granularity:
https://github.com/apache/cassandra/pull/3200
> CommitlogArchiver only has granularity to seconds for restore_point_in_time
> ---------------------------------------------------------------------------
>
> Key: CASSANDRA-19448
> URL: https://issues.apache.org/jira/browse/CASSANDRA-19448
> Project: Cassandra
> Issue Type: Bug
> Components: Local/Commit Log
> Reporter: Jeremy Hanna
> Assignee: Maxwell Guo
> Priority: Normal
> Fix For: 4.0.x, 4.1.x, 5.0.x, 5.x
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> Commitlog archiver allows users to backup commitlog files for the purpose of
> doing point in time restores. The [configuration
> file|https://github.com/apache/cassandra/blob/trunk/conf/commitlog_archiving.properties]
> gives an example of down to the seconds granularity but then asks what
> whether the timestamps are microseconds or milliseconds - defaulting to
> microseconds. Because the [CommitLogArchiver uses a second based date
> format|https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/db/commitlog/CommitLogArchiver.java#L52],
> if a user specifies to restore at something at a lower granularity like
> milliseconds or microseconds, that means that the it will truncate everything
> after the second and restore to that second. So say you specify a
> restore_point_in_time like this:
> restore_point_in_time=2024:01:18 17:01:01.623392
> it will silently truncate everything after the 01 seconds. So effectively to
> the user, it is missing updates between 01 and 01.623392.
> This appears to be a bug in the intent. We should allow users to specify
> down to the millisecond or even microsecond level. If we allow them to
> specify down to microseconds for the restore point in time, then it may
> internally need to change from a long.
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