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Date: Tue, 16 Jul 2013 19:02:49 +0000 (UTC)
From: "Tyler Hobbs (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
Message-ID: <JIRA.12657166.1373496858875.59727.1374001369752@arcas>
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Subject: [jira] [Commented] (CASSANDRA-5746) HHOM.countPendingHints is a
 trap for the unwary
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    [ https://issues.apache.org/jira/browse/CASSANDRA-5746?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13710088#comment-13710088 ] 

Tyler Hobbs commented on CASSANDRA-5746:
----------------------------------------

Doesn't the TTL on hints cells complicate all of those strategies?  I can't think of a cheap way to schedule all of those future decrements to a counter.

Instead, I suppose we could recount on demand if the time since the last count is greater than the smallest TTL we've seen, but without throttling of some sort recounts would still happen frequently under some circumstances.

Alternatively, it seems like a fair amount of work, but perhaps a get_range_counts() implementation with internal auto-paging (like get_count) is a decent option?
                
> HHOM.countPendingHints is a trap for the unwary
> -----------------------------------------------
>
>                 Key: CASSANDRA-5746
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-5746
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core, Tools
>            Reporter: Jonathan Ellis
>            Assignee: Tyler Hobbs
>             Fix For: 2.0.1
>
>
> countPendingHints can OOM the server fairly easily since it does a per-target seq scan without paging.
> More generally, countPendingHints is far too slow to be useful for routine monitoring.

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