Github user zentol commented on the issue:
https://github.com/apache/flink/pull/5100
yes, we _could_ setup all IO metrics in the operator chain. But that will
require some more changes there since the methods there never access 2
operators at the same time.
For a chain A->B, to setup the output of A you need metrics for both A and
B.
You cannot be "clever" and re-use the output metrics of A as the input
metrics for B, since this will cause odd results in forking chain scenarios
where the input metrics for both chained operators change at the same time even
though they are always processed sequentially. This would get even more funky
if an operator decides that it's input/output metrics are always supposed to be
identical, at which point you have metrics for 3 operators changing at the same
time.
But just thinking about modifying the `OperatorChain` sends shivers down my
spine âï¸
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