Handling errors in RPC Tokio tasks

[ceyhunsen]

Issue Description

Tokio tasks used in some RPC functions returns Result. But the handle of those tasks are never checked for errors after they finish. Possible errors are only related to Tokio channels and these errors can be discovered while testing. But because these errors are silent, developer might have a hard time finding the errors.

Example code:

clementine/core/src/rpc/verifier.rs

Lines 376 to 388 in da079a8

	tokio::spawn(async move {
	// First send the session id
	let session_id: NonceGenResponse = nonce_gen_first_response.into();
	tx.send(Ok(session_id)).await?;
	// Then send the public nonces
	for pub_nonce in &pub_nonces[..] {
	let pub_nonce: NonceGenResponse = pub_nonce.into();
	tx.send(Ok(pub_nonce)).await?;
	}
	Ok::<(), SendError<_>>(())
	});

There are multiple possible solutions to this.

Possible Solutions

• Convert ?'s to except() calls
• Write a task watcher background job that accepts task handles and logs them if anyone returns an Err
• Create a macro that spawns another infallible Tokio task that logs the main task's errors, if there are any
• Move a task's contents to a function with a #[tracing::instrument] so that tracing handles this

[mmtftr]

I've actually done solution #2 in some places when I was refactoring. I think it makes sense to go with 2 and maybe write a helper macro/function for it. Or we could write the inner as a function somewhere and add #[tracing::instrument] to it

[ceyhunsen]

@mmtftr I think you mentioned a wrong PR. Can you also edit the description and add the solution you provided as an option?

[mmtftr]

Yeah, didn't mean to mention a PR. I was referring to #(number)2. You can check

clementine/core/src/rpc/verifier.rs

Lines 503 to 511 in da079a8

	// Background task to handle the error case where the background task fails, notifies caller
	tokio::spawn(async move {
	if let Ok(Err(bg_err)) = handle.await {
	let ret_res = error_tx.send(Err(bg_err)).await;
	if let Err(SendError(Err(e))) = ret_res {
	tracing::error!("deposit_sign background task failed and the return stream ended prematurely:\n\n Background task error: {e}");
	}
	}
	});

for an example

[ceyhunsen]

OK, thanks. Added them as options