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From "Nick Bailey (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-2434) node bootstrapping can violate consistency
Date Wed, 14 Sep 2011 16:23:08 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-2434?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13104618#comment-13104618
] 

Nick Bailey commented on CASSANDRA-2434:
----------------------------------------

I had a note to remember to create a ticket for that, but if we want to do it here that works
as well.

In any case, yes the same concerns exist when giving away ranges as when gaining ranges.

> node bootstrapping can violate consistency
> ------------------------------------------
>
>                 Key: CASSANDRA-2434
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2434
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Peter Schuller
>            Assignee: paul cannon
>             Fix For: 1.0.1
>
>         Attachments: 2434-3.patch.txt, 2434-testery.patch.txt
>
>
> My reading (a while ago) of the code indicates that there is no logic involved during
bootstrapping that avoids consistency level violations. If I recall correctly it just grabs
neighbors that are currently up.
> There are at least two issues I have with this behavior:
> * If I have a cluster where I have applications relying on QUORUM with RF=3, and bootstrapping
complete based on only one node, I have just violated the supposedly guaranteed consistency
semantics of the cluster.
> * Nodes can flap up and down at any time, so even if a human takes care to look at which
nodes are up and things about it carefully before bootstrapping, there's no guarantee.
> A complication is that not only does it depend on use-case where this is an issue (if
all you ever do you do at CL.ONE, it's fine); even in a cluster which is otherwise used for
QUORUM operations you may wish to accept less-than-quorum nodes during bootstrap in various
emergency situations.
> A potential easy fix is to have bootstrap take an argument which is the number of hosts
to bootstrap from, or to assume QUORUM if none is given.
> (A related concern is bootstrapping across data centers. You may *want* to bootstrap
to a local node and then do a repair to avoid sending loads of data across DC:s while still
achieving consistency. Or even if you don't care about the consistency issues, I don't think
there is currently a way to bootstrap from local nodes only.)
> Thoughts?

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