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From "Sandeep Tata (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-497) Include bootstrap targets in consistencylevel computations
Date Tue, 20 Oct 2009 22:35:59 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-497?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12767989#action_12767989
] 

Sandeep Tata commented on CASSANDRA-497:
----------------------------------------

> Yes it does, because reads just use getReadStorageEndPoints, which correctly ignores
bootstrap-in-progress. 

Which is exactly why it might violate consistency guarantees. Here's an example:

Key k lives on A, B, C. Node  N is being bootstrapped for this range.

write(k, ConsistencyLevel.ONE) : blocks for 1 response, say this was from Node N.

read(k, ConsistencyLevel.ONE) --> gets data from one replica, say A. Node A might not yet
have gotten the previous write (only N did): this violates the consistency semantics.

> Include bootstrap targets in consistencylevel computations
> ----------------------------------------------------------
>
>                 Key: CASSANDRA-497
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-497
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Jonathan Ellis
>            Assignee: Jonathan Ellis
>            Priority: Minor
>             Fix For: 0.5
>
>         Attachments: 0001-CASSANDRA-497-rename-nodePicker-replicationStrategy.txt, 0002-make-write-targets-computable-independent-of-replicati.txt,
0003-Make-EndPoint-objects-immmutable-so-hashcode-can-t-ch.txt, imports.patch
>
>
> We want to preserve ConsistencyLevel semantics during bootstrap, and if a CL.quorum/all
write is sent to a bootstrap target, it would have to wait for the forwarded write to complete
to report in turn that the write is good.
> Leaving write propagation to be done by the write originator means we don't have this
extra layer of latency.

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