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From "Tyler Hobbs (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-5746) HHOM.countPendingHints is a trap for the unwary
Date Tue, 16 Jul 2013 20:08:48 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-5746?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13710160#comment-13710160
] 

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

> What if we redefine the problem to be "how many hints have I generated for node X?" and
get rid of countPendingHints entirely?

That seems like a reasonable replacement metric for most purposes, but I can see where countPendingHints()
might still be useful.  However, in its current state, it seems too dangerous to leave in.
 Maybe pull it out in this ticket and open a new ticket for a better implementation if there's
interest?

I'm assuming we don't want to persist this one to disk. (Most RRD-style metric systems handle
normally monotonically increasing metrics resetting to 0 occasionally, so just counting hints
created since the node has been up should be fine.)
                
> 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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