Make MonoSend.MAX_SIZE configurable by system property

[VadimKirilchuk]

MonoSend.MAX_SIZE is a constant used by MonoSendMany and its SendManyInner class to request initial items from a publisher to send to an output Channel. This PR introduces a way to configure MonoSend.MAX_SIZE by using reactor.netty.channel.send.prefetch.maxSize(Upd. reactor.netty.send.maxPrefetchSize) system property. A custom value for the property may be necessary if requested items from publisher are large and requesting default number of items (128) requires too much memory.

Fixes #3255

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[VadimKirilchuk]

@violetagg I did the change, some tests are failing locally, but seems to be unrelated.
I'll try to run my sample app with updated code and property to make sure it works fine.

[VadimKirilchuk]

I have also checked running that locally with some stub Flux Publisher:

        return Mono.just(ResponseEntity.ok()
                .body(Flux.<ByteBuffer>generate(sink -> sink.next(ByteBuffer.wrap(SAMPLE)))
                        .take(1024)
//                        .delayElements(Duration.ofMillis(100))
                        .doOnRequest(value -> log.info("Requested {}", value))));

2024-06-07T14:58:03.980-04:00  INFO 14288 --- [ctor-http-nio-2] o.e.s.controller.DownloadController      : New request
2024-06-07T14:58:04.031-04:00  INFO 14288 --- [ctor-http-nio-2] o.e.s.controller.DownloadController      : Requested 1
2024-06-07T14:58:04.079-04:00  INFO 14288 --- [ctor-http-nio-2] o.e.s.controller.DownloadController      : Requested 63
2024-06-07T14:58:04.121-04:00  INFO 14288 --- [ctor-http-nio-2] o.e.s.controller.DownloadController      : Requested 32

...

2024-06-07T14:58:04.290-04:00  INFO 14288 --- [ctor-http-nio-2] o.e.s.controller.DownloadController      : Requested 32
2024-06-07T14:58:04.296-04:00  INFO 14288 --- [ctor-http-nio-2] o.e.s.controller.DownloadController      : Requested 32
2024-06-07T14:58:04.300-04:00  INFO 14288 --- [ctor-http-nio-2] o.e.s.controller.DownloadController      : Requested 32
2024-06-07T14:58:04.331-04:00  INFO 14288 --- [ctor-http-nio-2] reactor.netty.http.server.AccessLog      : 0:0:0:0:0:0:0:1 - - [07/июн./2024:14:58:03 -0400] "GET /api/download HTTP/1.1" 200 3072 473

Seems to work as expected. Please let me know if you need anything else from my side.

Also, do you want me to create a similar PR for 1.2.x? I am not sure if you are simply doing merges from 1.1.x -> 1.2.x.

[violetagg]

@VadimKirilchuk

Also, do you want me to create a similar PR for 1.2.x? I am not sure if you are simply doing merges from 1.1.x -> 1.2.x.

There is no need. We use forward merge strategy, so the change is already available in the dev branches.

Thanks for the PR!