[jira] [Created] (FLINK-12126) Make relaxed rescaling behaviour accessible in REST interface

[Shang Yuanchun (Jira)]

Joshua Schneider created FLINK-12126:
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             Summary: Make relaxed rescaling behaviour accessible in REST interface
                 Key: FLINK-12126
                 URL: https://issues.apache.org/jira/browse/FLINK-12126
             Project: Flink
          Issue Type: Improvement
          Components: Runtime / REST
    Affects Versions: 1.7.2
            Reporter: Joshua Schneider


The REST handler for rescaling uses RescalingBehaviour.STRICT as a hard-coded parameter. This has the following consequences when a job is rescaled:

 * All operators are set to the new parallelism. If at least one operator's max parallelism is less than the new parallelism, the rescale operation is aborted.
 * Therefore, it is impossible to restrict the parallelism of a subset of operators (say, to one) in combination with rescaling.

A different behaviour which fixes these issues, RescalingBehaviour.RELAXED, is already provided by the internal API. However, it appears to be unused.

The REST interface should provide a parameter that selects the strategy. Alternatively, it could be a setting of the job.



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