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From "Jaakko Laine (JIRA)" <>
Subject [jira] Commented: (CASSANDRA-833) fix consistencylevel during bootstrap
Date Fri, 05 Mar 2010 14:10:27 GMT


Jaakko Laine commented on CASSANDRA-833:

This issue is not only related to bootstrapping, since nodes leaving the ring will also cause
pending ranges. If a node does not complete leaving operation properly, obsolete pending ranges
will be left in metadata.

(2) above is actually almost exactly how pending ranges is calculated. All current move operations
are finished and pending ranges is calculated according to what are the new natural endpoints
for the ranges in question.

This is not directly related to bootstrapping IMHO, but to the fact that node movement increases
quorum and due to node movement being uncertain, there is bigger possibility that something
goes wrong and quorum nodes cannot be reached.

> fix consistencylevel during bootstrap
> -------------------------------------
>                 Key: CASSANDRA-833
>                 URL:
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 0.5
>            Reporter: Jonathan Ellis
>            Assignee: Jaakko Laine
>             Fix For: 0.6
> As originally designed, bootstrap nodes should *always* get *all* writes under any consistencylevel,
so when bootstrap finishes the operator can run cleanup on the old nodes w/o fear that he
might lose data.
> but if a bootstrap operation fails or is aborted, that means all writes will fail until
the ex-bootstrapping node is decommissioned.  so starting in CASSANDRA-722, we just ignore
dead nodes in consistencylevel calculations.
> but this breaks the original design.  CASSANDRA-822 adds a partial fix for this (just
adding bootstrap targets into the RF targets and hinting normally), but this is still broken
under certain conditions.  The real fix is to consider consistencylevel for two sets of nodes:
>   1. the RF targets as currently existing (no pending ranges)
>   2.  the RF targets as they will exist after all movement ops are done
> If we satisfy CL for both sets then we will always be in good shape.
> I'm not sure if we can easily calculate 2. from the current TokenMetadata, though.

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