[jira] Commented: (CASSANDRA-640) Repair should never reuse a tree

["Jun Rao (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-640?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12792562#action_12792562 ] 

Jun Rao commented on CASSANDRA-640:
-----------------------------------

The patch looks reasonable to me.

> Repair should never reuse a tree
> --------------------------------
>
>                 Key: CASSANDRA-640
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-640
>             Project: Cassandra
>          Issue Type: Bug
>    Affects Versions: 0.5
>            Reporter: Stu Hood
>            Assignee: Stu Hood
>             Fix For: 0.5
>
>         Attachments: 640-one-use-tree-and-repair-frequency.diff
>
>
> AEService currently 'caches' MerkleTrees that have been generated by the local node, and can respond to a request for a tree with a cached version. This means that despite possibly having performed a repair, the two nodes will still be holding cached trees, and can respond to one another with the cached version, resulting in redundant repairs.
> Rather than a cache, the map of trees is intended to be a rendezvous point for two nodes to exchange relatively up-to-date trees. A map still might work, but other synchronization objects should be explored.

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