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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