Error handling

[hawkw]

Places where errors are discarded:

• client::Background::poll:

  tower-h2/src/client/background.rs

  Line 55 in e209b83

  Connection(ref mut f) => f.poll().map_err(|_| ()),

• Flush::poll:

  tower-h2/src/flush.rs

  Line 171 in e209b83

  self.poll_complete().map_err(|_| ())

• server::Background::poll:

  tower-h2/src/server/mod.rs

  Lines 454 to 455 in e209b83

  	// TODO: Do something with the error?
  	return Ok(().into());

Loss of specificity:

• server::Background::poll: error always sends an INTERNAL_ERROR:
  

  tower-h2/src/server/mod.rs

  Lines 430 to 432 in e209b83

  	// TODO: do something better the error?
  	let reason = Reason::INTERNAL_ERROR;
  	respond.send_reset(reason);

(N.B. that I'm still adding to the list)

[seanmonstar]

Something to consider is that hyper provides most (all?) of the functionality of tower-h2, we may be able to just switch to it entirely in Linkerd2.

[hawkw]

@seanmonstar

Maybe it's time? (cc @carllerche)

[carllerche]

@seanmonstar I mean, my hope was that the tower-h2 impl was available to use standalone and hyper used it to provide HTTP/2.0 support. I'm not sure how possible that is.