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From "Sylvain Lebresne (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-3455) Pending tasks should probably not include active tasks
Date Fri, 04 Nov 2011 17:29:52 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-3455?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13144188#comment-13144188
] 

Sylvain Lebresne commented on CASSANDRA-3455:
---------------------------------------------

bq. Hmm. The existing definition makes sense if you think of it as "not yet completed" instead
of "waiting."

Agreed, as said in the description I'm not arguing the existing definition doesn't make sense
per se, I'm arguing that it's probably not what people most naturally infer when they just
see the term 'pending tasks'. Obviously this is a bit objective, but it seems that everyone
(me included) I asked so far was indeed believing that pending tasks were the 'waiting' tasks
and were thus badly interpreting that number.

bq. Which is more useful, because otherwise you can have a bunch of executors saying "zero
pending tasks" but there is nothing to tell whether that is because the system isn't busy
or you just haven't maxed out on executor threads yet.

I'd argue that given we expose both active and pending, it's completely equivalent.

bq. TLDR: splitting into getActiveTasks/getQueueSize may make sense for 1.1, but we shouldn't
break things before then

Agreed.
                
> Pending tasks should probably not include active tasks
> ------------------------------------------------------
>
>                 Key: CASSANDRA-3455
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-3455
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 0.8.0, 1.0.0
>            Reporter: Sylvain Lebresne
>            Assignee: Sylvain Lebresne
>            Priority: Minor
>             Fix For: 0.8.8, 1.0.3
>
>         Attachments: 0001-Update-pending-task-count.patch
>
>
> In our TheadExecutor JMX metrics, 'pending tasks' includes 'active tasks' (because it's
taskCount-completedTaskCount). I think this is counter-intuitive for most people (of course
you could define 'pending tasks' as the 'pending of being fully executed' but you usually
want pending to indicate if there is tasks that have to wait to be executed). Besides, I believe
the initial intention was not to have pending to include active given the following comment:
> {noformat}
>     /**
>      * Get the number of tasks waiting to be executed
>      */
>     public long getPendingTasks()
> {noformat}
> This ticket propose to fix that.

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