sunhaibotb commented on a change in pull request #8124: [FLINK-11877] Implement
the runtime handling of the InputSelectable interface
URL: https://github.com/apache/flink/pull/8124#discussion_r276556081
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File path:
flink-runtime/src/main/java/org/apache/flink/runtime/io/network/partition/consumer/SingleInputGate.java
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@@ -184,6 +184,9 @@
/** A timer to retrigger local partition requests. Only initialized if
actually needed. */
private Timer retriggerLocalRequestTimer;
+ /** Flag indicating whether there is available data. */
+ private volatile boolean moreDataAvailable = false;
Review comment:
> We always should use either this BufferOrEvent#moreAvailable() or relay on
listeners/futures to inform us that the availability has changed
I don't think they can accurately determine the state (available or
unavailable). Considering the following execution sequences, the task thread
finally sees the same thing that `BufferOrEvent#moreAvailable` is false and
receives a non-null notification, but the last actual state of `InputGate` is
different, the former is available, and the latter is unavailable.
Case 1:
1. Initial State: `InputGate` is data available
2. (**Task Thread**) Call `InputGate#pollNextBufferOrEvent()`
3. (**Task Thread**) `InputGate` become empty after being polled a
`BufferOrEvent`
4. (**Task Thread**) Assign `BufferOrEvent#moreAvailable` to false before
returning
5. (**Network Thread**) Data arrives at `InputGate` which triggers the
non-empty notification
6. (**Task Thread**) `InputGate#pollNextBufferOrEvent()` returns,
`BufferOrEvent#moreAvailable` is false and recieves a `non-empty` notification
Case 2:
1. Initial State: `InputGate` is data unavailable
2. (**Task Thread**) Call `InputGate#pollNextBufferOrEvent()`
3. (**Network Thread**) Data arrives at `InputGate` which triggers the
non-empty notification
4. (**Task Thread**) `InputGate` become empty after being polled a
`BufferOrEvent`
5. (**Task Thread**) Assign `BufferOrEvent#moreAvailable` to false before
returning
6. (**Task Thread**) `InputGate#pollNextBufferOrEvent()` returns,
`BufferOrEvent#moreAvailable` is false and recieves a `non-empty` notification
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