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Date: Thu, 5 Jan 2012 23:01:39 +0000 (UTC)
From: "Brandon Williams (Commented) (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (CASSANDRA-3681) Multiple threads can attempt
 hint handoff to the same target
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    [ https://issues.apache.org/jira/browse/CASSANDRA-3681?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13180919#comment-13180919 ] 

Brandon Williams commented on CASSANDRA-3681:
---------------------------------------------

+1
                
> Multiple threads can attempt hint handoff to the same target
> ------------------------------------------------------------
>
>                 Key: CASSANDRA-3681
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3681
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 1.0.0
>            Reporter: Jonathan Ellis
>            Assignee: Jonathan Ellis
>            Priority: Minor
>              Labels: hintedhandoff
>             Fix For: 1.0.7
>
>         Attachments: 3681-v3.txt, 3681.txt, 3681v2.txt
>
>
> HintedHandOffManager attempts to prevent multiple threads sending hints to the same target with the queuedDeliveries set, but the code is buggy.  If two handoffs *do* occur concurrently, the second thread can use an arbitrarily large amount of memory skipping tombstones when it starts paging from the beginning of the hint row, looking for the first live hint.  (This is not a problem with a single thread, since it always pages starting with the last-seen hint column name, effectively skipping the tombstones.  Then it compacts when it's done.)
> Technically this bug is present in all older Cassandra releases, but it only causes problems in 1.0.x since the hint rows tend to be much larger (since there is one hint per write containing the entire mutation, instead of just one per row consisting of just the key).

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