Rui Fan created FLINK-40518:
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Summary: CDR is wrongly kept enabled on the aligned path when
unaligned checkpoint is disabled
Key: FLINK-40518
URL: https://issues.apache.org/jira/browse/FLINK-40518
Project: Flink
Issue Type: Sub-task
Components: Runtime / Checkpointing
Reporter: Rui Fan
Assignee: Rui Fan
`isCheckpointingDuringRecoveryEnabled` checks only
`UNALIGNED_RECOVER_OUTPUT_ON_DOWNSTREAM` and
`CHECKPOINTING_DURING_RECOVERY_ENABLED`, **not** `unaligned.enabled`
([CheckpointingOptions.java#L844-L849](https://github.com/apache/flink/blob/76e774e04ff84ea305714153c5f4790fff98437c/flink-core/src/main/java/org/apache/flink/configuration/CheckpointingOptions.java#L844-L849)).
So a job restoring from an unaligned checkpoint but running with UC disabled
still takes the CDR recovery branch
([StreamTask.java#L943-L945](https://github.com/apache/flink/blob/76e774e04ff84ea305714153c5f4790fff98437c/flink-runtime/src/main/java/org/apache/flink/streaming/runtime/tasks/StreamTask.java#L943-L945))
and goes RUNNING before the drain finishes.
But `InputProcessorUtil` threads `recoveryCheckpointTrigger` only into
`alternating()` (UC on); the `aligned()` handler used when UC is off gets
`NO_OP`
([InputProcessorUtil.java#L186-L199](https://github.com/apache/flink/blob/76e774e04ff84ea305714153c5f4790fff98437c/flink-runtime/src/main/java/org/apache/flink/streaming/runtime/io/checkpointing/InputProcessorUtil.java#L186-L199)).
The aligned path never considered a barrier delivered mid-recovery: the
barrier is stashed, so it can neither snapshot-during-recovery nor decline
`TASK_NOT_READY`. A checkpoint triggered in the recovery window hangs and
expires (`tolerable-failed-checkpoints` default 0) → failover loop.
**Fix**: the aligned path can't do CDR anyway, so don't enable CDR there — add
`&& isUnalignedCheckpointEnabled(config)` inside
`isCheckpointingDuringRecoveryEnabled`. It is the single central gate for all
CDR call sites, so UC-off falls every path back to the tested non-CDR recovery.
No functional loss.
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