The adaptive scheduler is a new scheduler which first declares the required resources and waits for them before deciding on the parallelism with which to execute a job. This behaviour has the benefit that Flink will be able to adjust the job to the available resources and to also make use of resources which arrive later. The details can be found in the FLIP-160.
This ticket serves as the umbrella for all the MVP targeted for Flink 1.13.0 (as described in FLIP-160). Improvements beyond the MVP are captured in there own tickets.