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Date: Wed, 16 Nov 2011 23:41:53 +0000 (UTC)
From: "Jonathan Ellis (Commented) (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (CASSANDRA-2434) range movements can violate
 consistency
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    [ https://issues.apache.org/jira/browse/CASSANDRA-2434?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13151640#comment-13151640 ] 

Jonathan Ellis commented on CASSANDRA-2434:
-------------------------------------------

No longer very optimistic on the "may even end up simpler overall than our current code" front?

TBH this area of the code is fragile and hairy and maybe starting from a clean slate with a real plan instead of trying to patch things in haphazardly would be a good thing.

But, I'd be okay with re-imposing the "no overlapping moves" rule and fixing the stream source problem if that's going to be substantially simpler.
                
> range movements 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: 1.0.4
>
>         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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