[jira] [Reopened] (FLINK-3315) Fix Slot Sharing in Streaming API

["Robert Metzger (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/FLINK-3315?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Robert Metzger reopened FLINK-3315:
-----------------------------------

> 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
>            Priority: Blocker
>             Fix For: 1.0.0
>
>
> 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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