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Date: Fri, 2 Sep 2016 08:53:20 +0000 (UTC)
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Subject: [jira] [Commented] (FLINK-4490) Decouple Slot and Instance
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archived-at: Fri, 02 Sep 2016 08:53:22 -0000


    [ https://issues.apache.org/jira/browse/FLINK-4490?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15457976#comment-15457976 ] 

ASF GitHub Bot commented on FLINK-4490:
---------------------------------------

Github user tillrohrmann commented on a diff in the pull request:

    https://github.com/apache/flink/pull/2447#discussion_r77313861
  
    --- Diff: flink-runtime/src/main/java/org/apache/flink/runtime/instance/SlotSharingGroupAssignment.java ---
    @@ -576,7 +560,7 @@ private void internalDisposeEmptySharedSlot(SharedSlot sharedSlot) {
     		
     		if (parent == null) {
     			// root slot, return to the instance.
    -			sharedSlot.getInstance().returnAllocatedSlot(sharedSlot);
    +			sharedSlot.getOwner().returnAllocatedSlot(sharedSlot);
    --- End diff --
    
    Can we use `sharedSlot.releaseSlot` instead? It seems not so right to get the owner which is then used to call `returnAllocatedSlot` with the same slot. I think this violates the law of Demeter.
    
    Alternatively, we could add a method `returnSlot` to `Slot` which does: `owner.returnAllocatedSlot(this)`.


> Decouple Slot and Instance
> --------------------------
>
>                 Key: FLINK-4490
>                 URL: https://issues.apache.org/jira/browse/FLINK-4490
>             Project: Flink
>          Issue Type: Sub-task
>          Components: Distributed Coordination
>            Reporter: Kurt Young
>             Fix For: 1.2.0
>
>
> Currently, {{Slot}} and {{Instance}} holds each other. For {{Instance}} holding {{Slot}}, it makes sense because it reflects how many resources it can provide and how many are using. 
> But it's not very necessary for {{Slot}} to hold {{Instance}} which it belongs to. It only needs to hold some connection information and gateway to talk to. Another downside for {{Slot}} holding {{Instance}} is that {{Instance}} actually contains some allocate/de-allocation logicals, it will be difficult if we want to do some allocation refactor without letting {{Slot}} noticed. 
> We should abstract the connection information of {{Instance}} to let {{Slot}} holds. (Actually we have {{InstanceConnectionInfo}} now, but lacks of instance's akka gateway, maybe we can just adding the akka gateway to the {{InstanceConnectionInfo}})


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