NIOTS doesn't let you control the equivalent of `maxMessagesPerRead` and `recvAllocator`

[weissi]

swift-nio-transport-services/Sources/NIOTransportServices/NIOTSConnectionChannel.swift

Lines 583 to 585 in 2ac8fde

	// TODO: Can we do something sensible with these numbers?
	self.outstandingRead = true
	conn.receive(minimumIncompleteLength: 1, maximumLength: 8192, completion: self.dataReceivedHandler(content:context:isComplete:error:))

NIOTS always does one underlying receive per read and always up to 8192.

So that kinda corresponds to:

• maxMessagesPerRead = 1
• recvAllocator = AdaptiveRecvAllocator(minimum: 1, maximum: 8192, initial: ???)

We should make those values configurable.

[edwellbrook]

Hi @weissi! Just came across this in one of my own projects and have some motivation to fix it.

This would be my first time contributing to to an swift-nio project, though I have some basic understanding of how things work. Some guidance would be appreciated...

Could you suggest what a good user-facing API would look like for configuring these values? Perhaps another option under NIOTSChannelOptions?

Thanks!

[weissi]

Hi @edwellbrook , awesome, and welcome! And thank you for your PR, I'll leave comments regarding your PR on the actual PR.

Were you separately from your existing PR (which configures the maximum read size) interested in working on maxMessagesPerRead?

[edwellbrook]

Unfortunately I don't have much need for maxMessagesPerRead so I can't budget the time for it right now. If my existing PR needs updating I might be able to quickly fit this in though!

Not super familiar with maxMessagesPerRead so would need a suggestion on how it's supposed to work and should be implemented.

[weissi]

@edwellbrook totally up to you. I fully understand if you can't budget the time. Ping me if you'd like an explanation of what it does exactly and how we could implement it.

[edwellbrook]

@weissi It's looking like I may need maxMessagesPerRead after all (if I'm understanding it correctly).

Does it refers to the number of messages an InboundChannelHandler will receive from a read call before needing to call read again? i.e. setting maxMessagesPerRead to 1 would mean an InboundChannelHandler needs to call read for each message?

If that's right... I'd love a suggestion on how to implement it.

Cheers!

[Lukasa]

Yup, that's exactly what it means.

In principle the mechanism to implement it should be simply to call .receive multiple times. I'm not 100% confident the code will handle that well, but that's how I'd go about starting out.

[edwellbrook]

@Lukasa Thanks! Will take a look tomorrow morning.