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From "Brandon Williams (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-981) Dynamic endpoint snitch
Date Sun, 15 Aug 2010 18:03:18 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-981?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12898717#action_12898717
] 

Brandon Williams commented on CASSANDRA-981:
--------------------------------------------

Committed to 0.6 and trunk.  Also worth noting that DES has been broken in trunk due to incorrectly
calculating the probability (needs to be 1 - Math.pow) which I fixed also.  We missed this
because the tests were wrong.

> Dynamic endpoint snitch
> -----------------------
>
>                 Key: CASSANDRA-981
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-981
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Core
>            Reporter: Jonathan Ellis
>            Assignee: Brandon Williams
>             Fix For: 0.6.5
>
>         Attachments: 981-0.6.txt, 981-fix-v2.txt, 981-fix.txt, 981.txt
>
>
> An endpoint snitch that automatically and dynamically infers "distance" to other machines
without having to explicitly configure rack and datacenter positions solves two problems:
> The killer feature here is adapting to things like compaction or a failing-but-not-yet-dead
disk.  This is important, since when we are doing reads we pick the "closest" replica for
actually reading data from (and only read md5s from other replicas).  This means that if the
closest replica by network topology is temporarily slow due to compaction (for instance),
we'll have to block for its reply even if we get the other replies much much faster.
> Not having to manually re-sync your configuration with your network topology when changes
(adding machines) are made is a nice bonus.

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