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From "Brandon Williams (JIRA)" <j...@apache.org>
Subject [jira] Updated: (CASSANDRA-981) Dynamic endpoint snitch
Date Tue, 08 Jun 2010 21:05:15 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-981?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Brandon Williams updated CASSANDRA-981:
---------------------------------------

    Attachment: 981.txt

There's a problem with this snitch: once a machine sees a host and sorts it to the end, it
will never read from that host again, meaning that it will never update that host's score,
until such time that another host performs worse.

Updated patch resolves this by resetting all the timing windows once per minute, giving the
'bad' hosts a chance to recover.

> 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: 0.7
>
>         Attachments: 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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