[jira] [Created] (FLINK-20427) Remove CheckpointConfig.setPreferCheckpointForRecovery because it can lead to data loss

["Till Rohrmann (Jira)" <ji...@apache.org>]

Till Rohrmann created FLINK-20427:
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             Summary: Remove CheckpointConfig.setPreferCheckpointForRecovery because it can lead to data loss
                 Key: FLINK-20427
                 URL: https://issues.apache.org/jira/browse/FLINK-20427
             Project: Flink
          Issue Type: Bug
          Components: API / DataStream, Runtime / Checkpointing
    Affects Versions: 1.12.0
            Reporter: Till Rohrmann
             Fix For: 1.13.0


The {{CheckpointConfig.setPreferCheckpointForRecovery}} allows to configure whether Flink prefers checkpoints for recovery if the {{CompletedCheckpointStore}} contains savepoints and checkpoints. This is problematic because due to this feature, Flink might prefer older checkpoints over newer savepoints for recovery. Since some components expect that the always the latest checkpoint/savepoint is used (e.g. the {{SourceCoordinator}}), it breaks assumptions and can lead to {{SourceSplits}} which are not read. This effectively means that the system loses data. Similarly, this behaviour can cause that exactly once sinks might output results multiple times which violates the processing guarantees. Hence, I believe that we should remove this setting because it changes Flink's behaviour in some very significant way potentially w/o the user noticing.



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