Grzegorz Liter created FLINK-37545:
--------------------------------------
Summary: StackOverflowError when using MetricGroup in custom
WatermarkStrategy
Key: FLINK-37545
URL: https://issues.apache.org/jira/browse/FLINK-37545
Project: Flink
Issue Type: Bug
Components: API / DataStream
Affects Versions: 1.20.1, 1.19.2
Reporter: Grzegorz Liter
When using MetricGroup to expose custom metrics in Watermark Generator
Example:
```
WatermarkStrategy
.forGenerator(ctx ->
new CustomWatermarkStrategy(ctx.getMetricGroup()))
.withTimestampAssigner((event, timestamp) -> ...);
```
StackOverflowError will be thrown.
This is due to changes done in https://issues.apache.org/jira/browse/FLINK-35886
Previously code in
`org.apache.flink.streaming.runtime.operators.TimestampsAndWatermarksOperator#open`
look like this:
```
watermarkGenerator =
emitProgressiveWatermarks
?
watermarkStrategy.createWatermarkGenerator(this::getMetricGroup)
: new NoWatermarksGenerator<>();
```
here in the `this::getMetricGroup` `this` refers to parent class instance
now it looks like this
```
watermarkGenerator =
emitProgressiveWatermarks
? watermarkStrategy.createWatermarkGenerator(
new WatermarkGeneratorSupplier.Context() {
@Override
public MetricGroup getMetricGroup() {
return this.getMetricGroup();
}
@Override
public RelativeClock
getInputActivityClock() {
return inputActivityClock;
}
})
: new NoWatermarksGenerator<>();
```
where `this` reference to anonymous class instance and causes infinite
recursive loop
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