Timo Walther created FLINK-23372:
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             Summary: Disable AllVerticesInSameSlotSharingGroupByDefault in 
DataStream batch mode
                 Key: FLINK-23372
                 URL: https://issues.apache.org/jira/browse/FLINK-23372
             Project: Flink
          Issue Type: Sub-task
          Components: API / DataStream
            Reporter: Timo Walther
            Assignee: Timo Walther


In order to unify the behavior of DataStream API and Table API batch mode, we 
should disable AllVerticesInSameSlotSharingGroupByDefault also in DataStream 
API.

FLINK-20001 reverted setting this flag but without concrete arguments and the 
following comment: {{reconsider actually setting this flag in the future}}

After a offline chat with [~zhuzh], we should introduce this again for 
consistency:

{code}
The goal to assign different regions to different slot sharing groups by 
default is to reduce waste of resources. In batch jobs, there can be one region 
which has data dependency on another region. And the resource computation for 
slots and managed memory will be affected:
  1 . If these regions are in the same slot sharing group, the group will 
require a large slot which can host tasks from both the regions.
  2. In managed memory fraction computing, tasks from both regions will be 
considered to compete for managed memory, so each task will be assigned with a 
smaller managed memory fraction (FLIP-53).

However, those regions will not run at the same time and results in a waste of 
resources. 

For streaming jobs, all tasks will run at the same time. So assigning them to 
the same slot sharing group will not result resource waste.
{code}



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