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From "Jonathan Ellis (Commented) (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-3690) Streaming CommitLog backup
Date Thu, 05 Apr 2012 21:54:23 GMT


Jonathan Ellis commented on CASSANDRA-3690:

Also: would be nice to get rid of the new Thread / busywait archive dance.  If we used an
ExecutorService instead, we could add the Future to the segment and just say segment.waitForArchive(),
no looping.
> Streaming CommitLog backup
> --------------------------
>                 Key: CASSANDRA-3690
>                 URL:
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Tools
>            Reporter: Vijay
>            Assignee: Vijay
>            Priority: Minor
>             Fix For: 1.1.1
>         Attachments: 0001-CASSANDRA-3690-v2.patch, 0001-Make-commitlog-recycle-configurable.patch,
0002-support-commit-log-listener.patch, 0003-helper-jmx-methods.patch, 0004-external-commitlog-with-sockets.patch,
> Problems with the current SST backups
> 1) The current backup doesn't allow us to restore point in time (within a SST)
> 2) Current SST implementation needs the backup to read from the filesystem and hence
additional IO during the normal operational Disks
> 3) in 1.0 we have removed the flush interval and size when the flush will be triggered
per CF, 
>           For some use cases where there is less writes it becomes increasingly difficult
to time it right.
> 4) Use cases which needs BI which are external (Non cassandra), needs the data in regular
intervals than waiting for longer or unpredictable intervals.
> Disadvantages of the new solution
> 1) Over head in processing the mutations during the recover phase.
> 2) More complicated solution than just copying the file to the archive.
> Additional advantages:
> Online and offline restore.
> Close to live incremental backup.
> Note: If the listener agent gets restarted, it is the agents responsibility to Stream
the files missed or incomplete.
> There are 3 Options in the initial implementation:
> 1) Backup -> Once a socket is connected we will switch the commit log and send new
updates via the socket.
> 2) Stream -> will take the absolute path of the file and will read the file and send
the updates via the socket.
> 3) Restore -> this will get the serialized bytes and apply's the mutation.
> Side NOTE: (Not related to this patch as such) The agent which will take incremental
backup is planned to be open sourced soon (Name: Priam).

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