Hey! First time posting to a mailing list, hope I did it correctly :)
I'm writing a master thesis at the University of Oslo and right now I'm looking at the performance overhead of using Beam with the Flink runnner versus plain Flink.
I've written a simple program, a custom source outputing 0, 1, 2, 3, up to N, going into a single identity operator and then int a filter which only matches N and prints that out. This is just to compare performance.
I've been doing some profiling of simple programs and one observation is the performance difference in the serialization. The hotspot is [1], which is used multiple places, but one place is [2], which is called from [3]. As far as I can tell, [1] seems to be implementing copying by first serializing and then deserializing and there are no way for the actual types to change this. In flink, you have control over the copy() method, like in [4] and so for certain types you can just do a simple return as you do here.
My queston is if I've understood the flow correctly so far and if so what the reason for doing it this way. Is it to avoid demanding that the type implement some type of cloning? And would it be possible to push this downward in the stack and allow the encoders to do define the copy schemantics? I'm willing to do the work here, just want to know if it would work on an arcitectural level.
If there is any known overheads of using beam that you would like to point out, I would love to hear about it.
Best regards, Teodor Spæren [1]: https://github.com/apache/beam/blob/master/sdks/java/core/src/main/java/org/apache/beam/sdk/util/CoderUtils.java#L140 [2]: https://github.com/apache/beam/blob/6fdde4f4eab72b49b10a8bb1cb3be263c5c416b5/runners/flink/1.8/src/main/java/org/apache/beam/runners/flink/translation/types/CoderTypeSerializer.java#L85 [3]: https://github.com/apache/beam/blob/6fdde4f4eab72b49b10a8bb1cb3be263c5c416b5/runners/flink/src/main/java/org/apache/beam/runners/flink/translation/types/CoderTypeInformation.java#L85 [4]: https://github.com/apache/flink/blob/master/flink-core/src/main/java/org/apache/flink/api/common/typeutils/base/LongSerializer.java#L53
