Hello, I got confused about usage of savepoints and checkpoints in different scenarios. I understand that checkpoints' main purpose is fault tolerance, they are more lightweight and don't support changing job graph, parallelism or state backend when restoring from them, as mentioned in the latest 1.13 docs: https://ci.apache.org/projects/flink/flink-docs-release-1.13/docs/ops/state/checkpoints/#difference-to-savepoints
At the same time: 1) Reactive scaling mode (in 1.13) uses checkpoints exactly for that - rescaling. 2) There are use cases like here: http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/What-happens-when-a-job-is-rescaled-td39462.html where people seem to be using retained checkpoints instead of savepoints to do manual job restarts with rescaling. 3) There are claims like here: https://lists.apache.org/thread.html/4299518f4da2810aa88fe6b21f841880b619f3f8ac264084a318c034%40%3Cuser.flink.apache.org%3E that in HA setup JobManager is able to restart from a checkpoint even if operators are added/removed or parallelism is changed (in this case I'm not sure if the checkpoints used by HA JM in `high-availability.storageDir` is the same thing as usual checkpoints). So I guess the questions are: 1) Can retained checkpoints be safely used for manual restarting and rescaling a job? 2) Are checkpoints made by HA JM structurally different from the usual ones? Can they be used to restore a job with a changed job graph? Thank you, Igor
