JSON-RPC queue is full too often

[tomaka]

Problem introduced in #793

The Full error is meant to indicate that there are too many requests in fly. Right now after only 4 requests it's already full.

This bound should be equal to the max_requests_in_fly:

smoldot/lib/src/json_rpc/service/client_main_task.rs

Line 141 in 12644b3

async_channel::bounded(config.serialized_requests_io_channel_size_hint.get());

Unfortunately, the underlying code does with_capacity(cap), so we can't set this to usize::max_value().

[tomaka]

This bound should be equal to the max_requests_in_fly:

Actually no, I need to revisit the entire stack of APIs. There are several people who don't seem to care about back-pressure here, so we need to give them some guarantees of success for the sending.

[tomaka]

Before #793, the behavior was indeed to simply check against max_requests_in_fly:

smoldot/lib/src/json_rpc/requests_subscriptions.rs

Lines 568 to 569 in ead9ea4

	let failed_to_increase = client
	.total_requests_in_fly

And yes, after some thought process it's the most sensical approach.

A client that doesn't want to care about this should simply set max_pending_requests to u32::max_value() when adding the chain.