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Questions about Savepoints


I have the following questions regarding savepoint recovery.

- In my job, it takes over 30 minutes to take a savepoint of over 100GB
  on 3 TMs. Most time spent after the alignment. I assume it was
  serialization and uploading to S3. However, when I resume a new job
  from the savepoint, it only takes seconds to recover. It seems too
  fast to me. I've tried resuming from the savepoint with a different
  parallelism. It was also very fast. Is this expected?

- Is there any log messages on the JM or the TMs indicating when a job
  or operator restored state from a savepoint? It'll be very helpful to
  know if state is restored especially when the
  "--allowNonRestoredState" flag is set.

- If a checkpoint was successfully taken after a savepoint, will
  resuming a job from the savepoint try to leverage the checkpoint?

- The job uses Kafka as the source, when I resume it from savepoint,
  when will the job start consuming from Kafka again? Does it wait until
  all operators have finished restoring state or does it start as soon
  as the source operator finishes restoring? I assume it waits for all
  because that's the only way to guarantee transactionality.

- When cancelling a job with a savepoint, is there anyway to prevent the
  job from cancelling if the savepoint fails? Otherwise, it sounds too
  dangerous to use this operation.

Thanks,

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Ning