Add autoPing for web sockets (ember server).

[kamilkloch]

autoPing flag is added to WebSocketBuilder2 (auto-ping should be arguably configurable per web socket connection).

Hovewer, actual ping is not materialized in WebSocketBuilder2.build, for performance reasons: concurrent merging of 2 fs2 streams (business logic and pings) is much more expensive than writing the ping frames directly into the socket.

WebSocketBuilder2.build provides a default (albeit less performant) implementation of auto-ping. Servers have the ability to override this implementation with a more performant direct write into the socket.

Closes #7347.

[armanbilge]

Hovewer, actual ping is not materialized in WebSocketBuilder2.build, for performance reasons:

Hmm, is this a compatibility issue: if we release this feature without a default implementation, what happens to all the servers that have not implemented yet?

If possible, we should implement the feature directly in WebSocketBuilder2.build. If there is a measurable difference in performance, then we can override it in servers implementations with a more efficient implementation.

[kamilkloch]

Hovewer, actual ping is not materialized in WebSocketBuilder2.build, for performance reasons:

Hmm, is this a compatibility issue: if we release this feature without a default implementation, what happens to all the servers that have not implemented yet?

If possible, we should implement the feature directly in WebSocketBuilder2.build. If there is a measurable difference in performance, then we can override it in servers implementations with a more efficient implementation.

As for performace difference:

val n = 10_000
val m = 100
val s = Stream(1).covary[IO].repeatN(n)
val s2 = s.mergeHaltL(Stream.empty)

s.compile.last.replicateA_(m).timed.map(_._1.toMillis).flatMap(IO.println) >>
s2.compile.last.replicateA_(m).timed.map(_._1.toMillis).flatMap(IO.println)

130
105394

Also, please take a look at this PR , where replacing mergeHaltL with a manual implementation from typelevel/fs2#3363 (BTW, ping! :) ) significantly reduced latency and reduced CPU pressure 5x: softwaremill/tapir#3393

Baking a default implementation of auto-ping into WebSocketBuilder2.build might be tricky - once we include the frames in receiveSend, there is no way back. It has to be done in some other way.

[kamilkloch]

@armanbilge please take a look: a default auto-ping implementation in WebSocketBuilder2, which can be overriden by the servers. WebSocketBuilder2 now needs Temporal, which breaks bincompat.

[armanbilge]

WebSocketBuilder2 now needs Temporal, which breaks bincompat.

What if we collect the Temporal[F] on the withAutoPing method? Then we don't need to break bincompat.

[kamilkloch]

WebSocketBuilder2 now needs Temporal, which breaks bincompat.

What if we collect the Temporal[F] on the withAutoPing method? Then we don't need to break bincompat.

How to do a natural transformation Temporal[F] ~> Temporal[G]? (needed in WebSocketBuilder2#imapK)

EDIT: done.

[kamilkloch]

@armanbilge What do you think?