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https://issues.apache.org/jira/browse/FLINK-3315?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15148658#comment-15148658
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ASF GitHub Bot commented on FLINK-3315:
---------------------------------------

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

    https://github.com/apache/flink/pull/1641#discussion_r53017220
  
    --- Diff: 
flink-streaming-java/src/main/java/org/apache/flink/streaming/api/transformations/StreamTransformation.java
 ---
    @@ -202,6 +203,29 @@ public String getUid() {
        }
     
        /**
    +    * Returns the slot sharing group of this transformation.
    +    *
    +    * @see #setSlotSharingGroup(String)
    +    */
    +   public String getSlotSharingGroup() {
    +           return slotSharingGroup;
    +   }
    +
    +   /**
    +    * Sets the slot sharing group of this transformation. Parallels 
instances of operations that
    --- End diff --
    
    Fixed


> Fix Slot Sharing in Streaming API
> ---------------------------------
>
>                 Key: FLINK-3315
>                 URL: https://issues.apache.org/jira/browse/FLINK-3315
>             Project: Flink
>          Issue Type: Improvement
>          Components: Streaming
>    Affects Versions: 1.0.0
>            Reporter: Aljoscha Krettek
>            Assignee: Aljoscha Krettek
>
> Right now, the slot sharing/resource group logic is a bit "nebulous". The 
> slot sharing group that operators are put in depends on the order in which 
> operations are created. For example, in this case:
> {code}
> Source a = env.source()
> Source b = env.source()
> a.map().startNewResourceGroup().sink() 
> b.map().sink()
> {code}
> We end up with two resource groups:
> - group 1: source a
> - group 2: map(), sink(), source b, map(), sink()
> The reason is that the slot sharing id is incremented when transforming the 
> {{startNewResouceGroup()}} call and all operators that are transformed 
> afterwards in graph traversal get that new slot sharing id.
> (There is also {{isolateResources()}} which can be used to isolate an 
> operator.)
> What I propose is to remove {{startNewResourceGroup()}} and 
> {{isolateResouces()}} and replace it with {{slotSharingGroup(String)}}. By 
> default, operations would be in slot sharing group "default". This allows 
> very fine grained control over what operators end up in which slot sharing 
> group. For example, I could have this topology:
> {code}
> Source a = env.source().slotSharingGroup("sources")
> Source b = env.source().slotSharingGroup("sources")
> a.map().slotSharingGroup("heavy a").sink().slotSharingGroup("sinks") 
> b.map().slotSharingGroup("heavy b").sink().slotSharingGroup("sinks")
> {code}
> Which would isolate the lightweight sources and sinks in a group and put 
> heavy operations inside their own slot groups.
> This is a bit more low level than the previous API and requires more calls 
> than a simple {{startNewResourceGroup()}} but I think not many people would 
> use this feature and this design makes it very clear what operations end up 
> in the same group.



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