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From "Jonathan Ellis (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-3690) Streaming CommitLog backup
Date Wed, 22 Feb 2012 19:39:49 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-3690?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13213911#comment-13213911
] 

Jonathan Ellis commented on CASSANDRA-3690:
-------------------------------------------

That does rule out using s3fs in read/write mode, but I imagine that would be a pretty bad
idea from a latency standpoint anyway.  But in the context of just mounting log files for
replay/recover, CommitLog uses RandomAccessReader which is ordinary buffered i/o.
                
> Streaming CommitLog backup
> --------------------------
>
>                 Key: CASSANDRA-3690
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3690
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Tools
>            Reporter: Vijay
>            Assignee: Vijay
>            Priority: Minor
>             Fix For: 1.1.1
>
>         Attachments: 0001-Make-commitlog-recycle-configurable.patch, 0002-support-commit-log-listener.patch,
0003-helper-jmx-methods.patch, 0004-external-commitlog-with-sockets.patch, 0005-cmmiting-comments-to-yaml.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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