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Posted to commits@cassandra.apache.org by "Jonathan Ellis (JIRA)" <ji...@apache.org> on 2012/09/20 19:26:07 UTC
[jira] [Commented] (CASSANDRA-3901) write endpoints are not treated
correctly, breaking consistency guarantees
[ https://issues.apache.org/jira/browse/CASSANDRA-3901?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13459764#comment-13459764 ]
Jonathan Ellis commented on CASSANDRA-3901:
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Am I misreading this, or is this the same as CASSANDRA-833? See especially https://issues.apache.org/jira/browse/CASSANDRA-833?focusedCommentId=13028232&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13028232
> write endpoints are not treated correctly, breaking consistency guarantees
> --------------------------------------------------------------------------
>
> Key: CASSANDRA-3901
> URL: https://issues.apache.org/jira/browse/CASSANDRA-3901
> Project: Cassandra
> Issue Type: Sub-task
> Components: Core
> Reporter: Peter Schuller
> Assignee: Peter Schuller
>
> I had a nagging feeling this was the case ever since I started wanting CASSANDRA-3833 and thinking about hot to handle the association between nodes in the read set and nodes in the write set.
> I may be wrong (please point me in the direct direction if so), but I see no code anywhere that tries to (1) apply consistency level to currently normal endpoints only, and (2) "connect" a given read endpoint with a future write endpoint such that they are tied together for consistency purposes (parts of these concerns probably is covered by CASSANDRA-2434 but that ticket is more general).
> To be more clear about the problem: Suppose we have a ring of nodes, with a single node bootstrapping. Now, for a given row key suppose reads are served by A, B and C while writes are to go to A, B, C and D. In other words, D is the node bootstrapping. Suppose RF is 3 and A,B,C,D is ring order. There are a few things required for correct behavior:
> * Writes acked by D must never be treated as sufficient to satisfy consistency level since until it is part of the read set it does not count towards CL on reads.
> * Writes acked by B must *not* be treated as sufficient to satisfy consistency level *unless* the same write is *also* acked by D, because once D enters the ring, B will no longer be counting towards CL on reads. The only alternative is to make the read succeed and disallow D from entering the ring.
> We don't seem to be handling this at all (and it becomes more complicated with arbitrary transitions).
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