[FLINK-39018][checkpoint] Support checkpoint for LocalInputChannel#27861
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.../src/main/java/org/apache/flink/runtime/io/network/partition/consumer/LocalInputChannel.java
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| // Priority events (e.g. unaligned checkpoint barriers) must notify downstream even | ||
| // when the subpartition is blocked. | ||
| // | ||
| // During recovery, once the upstream output channel state is fully restored, a | ||
| // RECOVERY_COMPLETION event (EndOfOutputChannelStateEvent) is emitted. This event | ||
| // blocks the subpartition to prevent the upstream from sending new data while the | ||
| // downstream is still consuming recovered buffers. The subpartition remains blocked | ||
| // until the downstream finishes consuming all recovered buffers from every channel | ||
| // and calls resumeConsumption() to unblock. | ||
| // | ||
| // If a checkpoint is triggered while the downstream is still consuming recovered | ||
| // buffers, the upstream receives an unaligned checkpoint barrier and adds it to this | ||
| // blocked subpartition. The barrier must still be delivered to the downstream | ||
| // immediately, otherwise the checkpoint will hang until it times out. | ||
| return buffers.getNumPriorityElements() == 1; |
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Explaining why Priority events (e.g. unaligned checkpoint barriers) must notify downstream even when the subpartition is blocked.
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...test/java/org/apache/flink/runtime/io/network/partition/consumer/RemoteInputChannelTest.java
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...me/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/SingleInputGate.java
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…r availability for recovered buffers
…n if it is blocked to ensure the checkpoint barrier can be handled by downstream task Priority events (e.g. unaligned checkpoint barriers) must notify downstream even when the subpartition is blocked. During recovery, once the upstream output channel state is fully restored, a RECOVERY_COMPLETION event (EndOfOutputChannelStateEvent) is emitted. This event blocks the subpartition to prevent the upstream from sending new data while the downstream is still consuming recovered buffers. The subpartition remains blocked until the downstream finishes consuming all recovered buffers from every channel and calls resumeConsumption() to unblock. If a checkpoint is triggered while the downstream is still consuming recovered buffers, the upstream receives an unaligned checkpoint barrier and adds it to this blocked subpartition. The barrier must still be delivered to the downstream immediately, otherwise the checkpoint will hang until it times out.
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Thanks @pnowojski for the review, all comments are addressed, and commits are organized.
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This PR depends on #27782 and #27783
What is the purpose of the change
[FLINK-39018][checkpoint] Support checkpoint for LocalInputChannel
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@Public(Evolving): noDocumentation