Jiayi Liao created FLINK-23208:
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Summary: Late processing timers need to wait 1ms at least to be
fired
Key: FLINK-23208
URL: https://issues.apache.org/jira/browse/FLINK-23208
Project: Flink
Issue Type: Bug
Components: Runtime / Task
Affects Versions: 1.11.0
Reporter: Jiayi Liao
The problem is from the codes below:
```
public static long getProcessingTimeDelay(long processingTimestamp, long
currentTimestamp) {
// delay the firing of the timer by 1 ms to align the semantics with
watermark. A watermark
// T says we won't see elements in the future with a timestamp smaller
or equal to T.
// With processing time, we therefore need to delay firing the timer by
one ms.
return Math.max(processingTimestamp - currentTimestamp, 0) + 1;
}
```
Assuming a Flink job creates 1 timer per millionseconds, and is able to consume
1 timer/ms. Here is what will happen:
* Timestmap1(1st ms): timer1 is registered and will be triggered on Timestamp2.
* Timestamp2(2nd ms): timer2 is registered and timer1 is triggered
* Timestamp3(3rd ms): timer3 is registered and timer1 is consumed, after this,
{{InternalTimerServiceImpl}} registers next timer, which is timer2, and timer2
will be triggered on Timestamp4(wait 1ms at least)
* Timestamp4(4th ms): timer4 is registered and timer2 is triggered
* Timestamp5(5th ms): timer5 is registered and timer2 is consumed, after this,
{{InternalTimerServiceImpl}} registers next timer, which is timer3, and timer3
will be triggered on Timestamp6(wait 1ms at least)
As we can see here, the ability of the Flink job is consuming 1 timer/ms, but
it's actually able to consume 0.5 timer/ms.
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