[jira] [Created] (FLINK-19701) Unaligned Checkpoint might misuse the number of buffers to persist from the previous barrier

["Yun Gao (Jira)" <ji...@apache.org>]

Yun Gao created FLINK-19701:
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             Summary: Unaligned Checkpoint might misuse the number of buffers to persist from the previous barrier
                 Key: FLINK-19701
                 URL: https://issues.apache.org/jira/browse/FLINK-19701
             Project: Flink
          Issue Type: Bug
          Components: Runtime / Checkpointing
    Affects Versions: 1.12.0
            Reporter: Yun Gao


Current CheckpointUnaligner interacts with RemoteInputChannel to persisting the input buffers. However, based the current implementation it seems if we have the following case:
{code:java}
1. There are 3 input channels.
2. Input channel 0 received barrier 1, and processed barrier 1 to start checkpoint 1.
3. Input channel 1 received barrier 1, and processed barrier 1. Now the state of input channel persister becomes BARRIER_RECEIVED and numBuffersOvertaken(channel 1) = n_1.
4. However, input 2 received nothing and the checkpoint expired, new checkpoint is trigger.
5. Input channel 0 received barrier 2, checkpoint 1 is deserted and checkpoint 2 is started. However, in this case the state of the input channels are not cleared. Thus now channel 1 is still BARRIER_RECEIVED and numBuffersOvertaken(channel 1) = n_1. Then channel 1 would only persist n_1 buffers in the channel. 

{code}



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