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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-1872) Provide ability send notifications via JMX when an SSTable is written
Date Fri, 04 Mar 2011 15:19:36 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13002657#comment-13002657
] 

Jonathan Ellis commented on CASSANDRA-1872:
-------------------------------------------

bq. the notification missing is indeed possible. but it's practically impossible if you setup
the listener on the same host as cassandra/JMX server.  in the rare event that data is lost,
we do use this in conjunction with complete snapshot backup

The problem is that you can miss things without _knowing_ you missed them.  That's why it's
so dangerous.

bq. crawling the FS was indeed one of our original thoughts, but here you face the issue that
you could lose the fresh level-0 SStables after they are compacted

It sounds like in this case you still have a window of a race where you tell the listener
"new SSTable X is available" and by the time the listener goes to back it up it's been compacted.
 Granted, this is unlikely, but it is technically possible.

As an alternative, what if we added an option to "snapshot" (that is, hard link -- not a full
snapshot of the entire CF) newly-flushed sstables somewhere so a backup script can get an
easy guarantee of seeing them without any interference?

> Provide ability send notifications via JMX when an SSTable is written
> ---------------------------------------------------------------------
>
>                 Key: CASSANDRA-1872
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1872
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Tools
>            Reporter: Nate McCall
>         Attachments: full.diff, jmockit-0.999.5.jar
>
>
> One application of interest is the immediate backup of new SSTables. Relying on JMX's
MBeanNotificationInfo would be a minimally intrusive to add "listeners" to CFS to facilitate
this. 

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