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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] Updated: (CASSANDRA-483) clean up bootstrap code, 2
Date Mon, 26 Oct 2009 21:19:00 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-483?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jonathan Ellis updated CASSANDRA-483:
-------------------------------------

    Attachment:     (was: 0002-refactor-bootstrap-to-only-concern-itself-with-bootstr.txt)

> clean up bootstrap code, 2
> --------------------------
>
>                 Key: CASSANDRA-483
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-483
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Tools
>            Reporter: Jonathan Ellis
>            Assignee: Jonathan Ellis
>             Fix For: 0.5
>
>         Attachments: 0001-CASSANDRA-483-r-m-single-use-executor-in-favor-of-a-Th.txt,
0002-refactor-bootstrap-to-only-concern-itself-with-bootstr.txt
>
>
> existing bootstrap code overengineers things a bit by allowing multiple nodes to bootstrap
into the same span of the ring simultaneously.  but, this doesn't handle the case where one
of them doesn't complete the bootstrap.  one possible response would be to transfer that node's
span to one of the other new nodes, but then you're no longer evenly dividing the ring.  starting
over with recomputed tokens for the remaining nodes is significantly complicated.
> in short I think the right solution is to handle each node independently.   if only one
node bootstraps into a ring segment at a time, nothing changes.  but if another node bootstraps
in before the first finishes, we just say "okay" and send them each the data they would get
_if it were the only node bootstrapping_.  So if one fails, we don't have to do any extra
work.  If all succeed, the penalty is we transferred too much to some nodes but that will
be taken care of by the existing cleanup compaction code.
> (this does mean that we can't automatically pick tokens while a bootstrap is in progress,
though, or it will pick the same one for both, which is undesireable.  but saying "if you
want to bootstrap multiple nodes into the same ring span at once, you have to manually specify
the tokens" seems reasonable to me.  (especially since that was already the case under the
old system, if you didn't want just random tokens.)

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