[jira] [Commented] (STORM-658) config topology.acker.executors default value is null and then should not start acker bolts

["Derek Dagit (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/STORM-658?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14598635#comment-14598635 ] 

Derek Dagit commented on STORM-658:
-----------------------------------

This Issue raises a valid point that Storm's behavior with a null value for {{topology.acker.executors}} might seem surprising.  Whether or not the Acker Executors will be used depends on the code.  If the topology components intend to make use of Acking, then it would be good for the common case to be handled. One Acker Executor per Worker seems like a good default here, so I am not too interested in changing it. I could be convinced otherwise.

What we might want to do instead is change the documentation—both the Markdown and the JavaDoc—to explicitly describe what the default behavior is.  We would want to update the description in Config.java and update our document titled "Guaranteeing Message Processing."  (Incidentally, the latter document already describes how to disable launching of the Acker Executors if you know that you do not want acking, which is to use {{0}}.)

We might also want to either update the example Topologies to actually make use of acking or else update them not to launch the Ackers at all so as to avoid possibly confusing users.

Another thought is that perhaps we should not count Executors that are devoted to running system Tasks like the Acker on the UI Topology Summary, since we have a button at the bottom that enables or disables inclusion of the system stats.  I looked at the UI code, and it seems we have been counting Acker Executors in the Topology Summary for a very long time.  So far we have simply counted all the Executors in the Topology whether or not the user asked to show System Stats.


> config topology.acker.executors default value is null and then should not start acker bolts
> -------------------------------------------------------------------------------------------
>
>                 Key: STORM-658
>                 URL: https://issues.apache.org/jira/browse/STORM-658
>             Project: Apache Storm
>          Issue Type: Bug
>            Reporter: caofangkun
>            Assignee: caofangkun
>            Priority: Minor
>         Attachments: executors num is wrong.png, is null.png
>
>
> See Code:
> https://github.com/caofangkun/apache-storm/blob/master/storm-core/src/clj/backtype/storm/daemon/common.clj#L315
> Config "topology.acker.executors" default value is null
> then acker executors will be same as "topology.workers"
> $ storm jar storm-starter-0.10.0-SNAPSHOT.jar storm.starter.ExclamationTopology ExclamationTopology
> Executors show up as 18 executors = 10(word) + 3(exclaim1) + 2(exclaim2) + 3(acker bolt)
> But the 3 acker bolt executors will not be used.



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