[jira] [Comment Edited] (CASSANDRA-9591) Scrub (recover) sstables even when -Index.db is missing

["Benedict (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-9591?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14613048#comment-14613048 ] 

Benedict edited comment on CASSANDRA-9591 at 7/3/15 9:31 AM:
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Perhaps we should just {{obsoleteOriginals}} up-front, if offline? We could even do it in the {{StandaloneScrubber}}, before calling {{scrubber.scrub()}}, to avoid polluting the general purpose {{Scrubber}}.

No strong feelings though - the patch looks like it works to me.

[~stefania]: could you rebase your branches and once CI passes I'll commit.


was (Author: benedict):
Perhaps we should just {{obsoleteOriginals}} up-front, if offline? We could even do it in the {{StandaloneScrubber}}, before calling {{scrubber.scrub()}}, to avoid polluting the general purpose {{Scrubber}}.

No strong feelings though - the patch looks like it works to me.

[~stef1927]: could you rebase your branches and once CI passes I'll commit.

> Scrub (recover) sstables even when -Index.db is missing
> -------------------------------------------------------
>
>                 Key: CASSANDRA-9591
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9591
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: mck
>            Assignee: mck
>              Labels: benedict-to-commit, sstablescrub
>             Fix For: 2.0.x
>
>         Attachments: 9591-2.0.txt, 9591-2.1.txt
>
>
> Today SSTableReader needs at minimum 3 files to load an sstable:
>  - -Data.db
>  - -CompressionInfo.db 
>  - -Index.db
> But during the scrub process the -Index.db file isn't actually necessary, unless there's corruption in the -Data.db and we want to be able to skip over corrupted rows. Given that there is still a fair chance that there's nothing wrong with the -Data.db file and we're just missing the -Index.db file this patch addresses that situation.
> So the following patch makes it possible for the StandaloneScrubber (sstablescrub) to recover sstables despite missing -Index.db files.
> This can happen from a catastrophic incident where data directories have been lost and/or corrupted, or wiped and the backup not healthy. I'm aware that normally one depends on replicas or snapshots to avoid such situations, but such catastrophic incidents do occur in the wild.
> I have not tested this patch against normal c* operations and all the other (more critical) ways SSTableReader is used. i'll happily do that and add the needed units tests if people see merit in accepting the patch.
> Otherwise the patch can live with the issue, in-case anyone else needs it. There's also a cassandra distribution bundled with the patch [here|https://github.com/michaelsembwever/cassandra/releases/download/2.0.15-recover-sstables-without-indexdb/apache-cassandra-2.0.15-recover-sstables-without-indexdb.tar.gz] to make life a little easier for anyone finding themselves in such a bad situation.



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