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https://issues.apache.org/jira/browse/FLINK-3315?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15150571#comment-15150571
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ASF GitHub Bot commented on FLINK-3315:
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Github user aljoscha commented on the pull request:
https://github.com/apache/flink/pull/1641#issuecomment-185230357
rebasing
> 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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