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From shixiaogang <...@git.apache.org>
Subject [GitHub] flink pull request #3801: [FLINK-6364] [checkpoints] Implement incremental c...
Date Wed, 03 May 2017 14:54:20 GMT
Github user shixiaogang commented on a diff in the pull request:

    https://github.com/apache/flink/pull/3801#discussion_r114565991
  
    --- Diff: flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/tasks/StreamTask.java
---
    @@ -769,9 +769,10 @@ public OperatorStateBackend createOperatorStateBackend(
     		cancelables.registerClosable(keyedStateBackend);
     
     		// restore if we have some old state
    -		if (null != restoreStateHandles && null != restoreStateHandles.getManagedKeyedState())
{
    -			keyedStateBackend.restore(restoreStateHandles.getManagedKeyedState());
    -		}
    +		Collection<KeyedStateHandle> restoreKeyedStateHandles =
    +			restoreStateHandles == null ? null : restoreStateHandles.getManagedKeyedState();
    +
    +		keyedStateBackend.restore(restoreKeyedStateHandles);
    --- End diff --
    
    I attempted to put the restore state in the constructor as we discussed. But it turns
out impossible. 
    
    All state backends should be registered in the task so that the backends can be closed
when the task is canceled.  If we put the restoring in the constructor of the backends, the
construction of the backends may be blocked (e.g., due to the access to HDFS). Since the construction
is not completed yet, the backend will not be registered and hence will not be closed.


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