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Date: Thu, 10 Nov 2016 20:14:58 +0000 (UTC)
From: "Raghu Angadi (JIRA)" <jira@apache.org>
To: commits@beam.incubator.apache.org
Message-ID: <JIRA.13019932.1478808706000.247799.1478808898443@Atlassian.JIRA>
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Subject: [jira] [Commented] (BEAM-958) desiredNumWorkers in Dataflow is too
 low
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archived-at: Thu, 10 Nov 2016 20:15:03 -0000


    [ https://issues.apache.org/jira/browse/BEAM-958?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15655020#comment-15655020 ] 

Raghu Angadi commented on BEAM-958:
-----------------------------------

A change to this policy can break Dataflow job update depending the source as update requires number of sources to remain same across an update. Native pubsub source is not affected.  

> desiredNumWorkers in Dataflow is too low
> ----------------------------------------
>
>                 Key: BEAM-958
>                 URL: https://issues.apache.org/jira/browse/BEAM-958
>             Project: Beam
>          Issue Type: Improvement
>          Components: runner-dataflow
>    Affects Versions: 0.3.0-incubating
>            Reporter: Raghu Angadi
>            Assignee: Davor Bonaci
>              Labels: breaking_change
>
> {{desiredNumWorkers}} in [UnboundedSource API|https://github.com/apache/incubator-beam/blob/v0.3.0-incubating-RC1/sdks/java/core/src/main/java/org/apache/beam/sdk/io/UnboundedSource.java#L69] is a suggestion to a source about how many splits it should create. KafkaIO currently takes this literally and only creates up to this many splits.
> The main draw back is that it is very low in Dataflow. It is calculated as 
>   * {{1 * maxNumWorkers}} if {{--maxNumWorkers}} is specified, otherwise
>   * {{3 * numWorkers}}.
> That implies there is only single reader per worker (which is usually a 4 core VM). That can leave CPU under utilized on many pipelines.
> Even 3x in case of fixes number of workers seems low to me. 


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