We've been looking into ways to support programmatic rescaling of job vertices. This feature is typically required for any type of Flink autoscaler which does not merely set the default parallelism but adjusts the parallelisms on a JobVertex level.
We've had an initial discussion here: https://issues.apache.org/jira/browse/FLINK-29501 where Chesnay suggested to use the infamous "rescaling" API: https://nightlies.apache.org/flink/flink-docs-master/docs/ops/rest_api/#jobs-jobid-rescaling This API is disabled as of https://issues.apache.org/jira/browse/FLINK-12312 . Since there is the Adaptive Scheduler in Flink now, it may be feasible to re-enable the API (at least for streaming jobs) and allow overriding the parallelism of job vertices in addition to the default parallelism. Any thoughts? -Max
