OperatorPublish benchmark

[akarnokd]

Benchmarks the behavior of publish() in face of number of child subscribers, batching effect in request(), length of the source and whether or not each child observes values on a separate thread.

Benchmark results

Remarks:

• With no subscribers, the operator seems to fill its queue and then do nothing unless someone subscribes. There is no test to check for this behavior so it might be a bug or a feature.
• In async mode, the benchmark threw MissingBackpressureException a lot of times which can happen with a single subscriber as well, so it might be some concurrency bug in the operator.

[benjchristensen]

The operator seems to fill its queue and then do nothing unless someone subscribes

I remember this being talked about at some point and an agreement that this is wrong behavior. If there are no subscribers it should just ignore/drop the data.

[benjchristensen]

Agreed that throwing a MissingBackpressureException a lot sounds like a problem.

[akarnokd]

There shouldn't be any MBE because every component supports backpressure. There is a request accounting problem somewhere but this is now irrelevant. The new OperatorPublish works without throwing MBE.