Github user zentol commented on the issue:
https://github.com/apache/flink/pull/2210
It gets an IOMG because in the past it would forward this group to its
deserializers, for Input byte counting etc. . I didn't change it cause i forgot
about my own convention on how to use the IOMG.
The IOMG only exist for the purpose of keeping details out of the TaskMG
(the getters mostly), and to prevent users of the IMOG to be able to access
other SubGroups of the TaskMG (separation of concerns). There is de-facto no
difference between a metric registered on a TaskMG or IOMG.
Thus, the underlying issue imo is that the IOMG extends
AbstractMetricGroup; giving it more functionality than it should have. Instead
it should extend a class as outlined below.
```
public abstract class SubMetricGroup<P extends MetricGroup> implements
MetricGroup {
private P parent;
public SubMetricGroup(P parent) {
this.parent = parent;
}
@Override
public Counter counter(int name) {
return parent.counter(name);
}
@Override
public Counter counter(String name) {
return parent.counter(name);
}
@Override
public <C extends Counter> C counter(int name, C counter) {
return parent.counter(name, counter);
}
@Override
public <C extends Counter> C counter(String name, C counter) {
return parent.counter(name, counter);
}
@Override
public <T, G extends Gauge<T>> G gauge(int name, G gauge) {
return parent.gauge(name, gauge);
}
@Override
public <T, G extends Gauge<T>> G gauge(String name, G gauge) {
return parent.gauge(name, gauge);
}
@Override
public <H extends Histogram> H histogram(String name, H histogram) {
return parent.histogram(name, histogram);
}
@Override
public <H extends Histogram> H histogram(int name, H histogram) {
return parent.histogram(name, histogram);
}
@Override
public MetricGroup addGroup(int name) {
return parent.addGroup(name);
}
@Override
public MetricGroup addGroup(String name) {
return parent.addGroup(name);
}
```
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