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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-9195) commitlog replay only actually replays mutation every other time
Date Thu, 23 Apr 2015 04:19:39 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-9195?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14508429#comment-14508429
] 

Jonathan Ellis commented on CASSANDRA-9195:
-------------------------------------------

Yes, it sounds to me like the restore is being "too clever."  Truncate means "I don't want
the data before now anymore."  PITR shouldn't truncate.

Edit: that said, it's valid to want to restore after a user incorrectly truncates.  I think
you'll need to edit the system keyspace before restoring.

> commitlog replay only actually replays mutation every other time
> ----------------------------------------------------------------
>
>                 Key: CASSANDRA-9195
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9195
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Jon Moses
>            Assignee: Branimir Lambov
>            Priority: Critical
>             Fix For: 2.1.5
>
>         Attachments: loader.py
>
>
> Version: Cassandra 2.1.4.374 | DSE 4.7.0
> The main issue here is that the restore-cycle only replays the mutations
> every other try.  On the first try, it will restore the snapshot as expected
> and the cassandra system load will show that it's reading the mutations, but
> they do not actually get replayed, and at the end you're left with only the
> snapshot data (2k records).
> If you re-run the restore-cycle again, the commitlogs are replayed as expected,
> and the data expected is present in the table (4k records, with a spot check of 
> record 4500, as it's in the commitlog but not the snapshot).
> Then if you run the cycle again, it will fail.  Then again, and it will work. The work/
> not work pattern continues.  Even re-running the commitlog replay a 2nd time, without
> reloading the snapshot doesn't work
> The load process is:
> * Modify commitlog segment to 1mb
> * Archive to directory
> * create keyspace/table
> * insert base data
> * initial snapshot
> * write more data
> * capture timestamp
> * write more data
> * final snapshot
> * copy commitlogs to 2nd location
> * modify cassandra-env to replay only specified keyspace
> * modify commitlog properties to restore from 2nd location, with noted timestamp
> The restore cycle is:
> * truncate table
> * sstableload snapshot
> * flush
> * output data status
> * restart to replay commitlogs
> * output data status
> ====
> See attached .py for a mostly automated reproduction scenario.  It expects DSE (and I
found it with DSE 4.7.0-1), rather than "actual" Cassandra, but it's not using any DSE specific
features.  The script looks for the configs in the DSE locations, but they're set at the top,
and there's only 2 places where dse is restarted.



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