https://build.spring.io/browse/INT-MASTER-467/
Even if `EmitterProcessor` looks good for us not requesting until real `subscriber()`, it doesn't keep backlog for late subscribers like it happens some times in our subscriber in the separate Thread.
The solution should be considered as tentative because the real one must be based on the fact that `AMPH` has to perform `subscription.request(n)` as a fact of the subscription from downstream.
In other words mid-flow components should work as passive subscribers and be based on downstream demand
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