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From "Paulo Motta (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8928) Add downgradesstables
Date Thu, 24 Mar 2016 00:44:25 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8928?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15209507#comment-15209507
] 

Paulo Motta commented on CASSANDRA-8928:
----------------------------------------

LGTM, a few nits in your updated proposal:
* Update {{We will start working with ma (3.0.x) and jb (2.2.x) formats}} to ma and la.
* Maybe add [ccm|https://github.com/pauloricardomg/ccm] tool to {{Familiarize with Cassandra
dtest suit.}}

bq. In addition, do you mean with double cycle support that our sstabledowngrader should work
correctly with a flow like "ma" -> "ka" -> "la"?

Would be something like ma -> la -> ma -> la -> ma and check the data is correct.
please note that upgrade from la -> ma is already supported via the upgradesstables tool
and you would add support to downgrade from ma -> la via the sstabledowngrader tool. Actually
{{StandaloneUpgrader}} is probably more relevant then {{SStableScrubber}} in this context
so you should mention this in your proposal instead(although sstable scrubber is also important
for learning purposes because it validates the sstable when reading). You should also probably
have a look on {{OldFormatIterator}} and {{OldFormatDeserializer}} classes to learn how sstables
are read in the previous format during your familiarization period.

Another thing that could possibly help in your Apache GSoC application is to work on a [low
hanging fruit ticket|https://issues.apache.org/jira/browse/CASSANDRA-11352?jql=project%20%3D%20CASSANDRA%20AND%20status%20%3D%20Open%20AND%20labels%20%3D%20lhf]
to prove your ability to dive into a complex codebase (CASSANDRA-8888 and CASSANDRA-8777 are
probably good for beginners). Please note that this is not required, but would only be a plus
in your application to the Apache selection committee and does not need to be done before
the application deadline since the decision will probably be taken only a few weeks after
that.

> Add downgradesstables
> ---------------------
>
>                 Key: CASSANDRA-8928
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-8928
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Tools
>            Reporter: Jeremy Hanna
>            Priority: Minor
>              Labels: gsoc2016, mentor
>
> As mentioned in other places such as CASSANDRA-8047 and in the wild, sometimes you need
to go back.  A downgrade sstables utility would be nice for a lot of reasons and I don't know
that supporting going back to the previous major version format would be too much code since
we already support reading the previous version.



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