PoV Distribution optimization (#1990)

* Initial commit

* Remove unnecessary struct

* Some review nits

* Update node/network/pov-distribution/src/lib.rs

* Update parachain/test-parachains/adder/collator/tests/integration.rs

* Review nits

* notify_all_we_are_awaiting

* Both ways of peers connections should work the same

* Add mod-level docs to error.rs

* Avoid multiple connection requests at same parent

* Dont bail on errors

* FusedStream for ConnectionRequests

* Fix build after merge

* Improve error handling

* Remove whitespace formatting

polkadot/node/network/pov-distribution/src/error.rs

@@ -0,0 +1,35 @@
+// Copyright 2020 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! The `Error` and `Result` types used by the subsystem.
+
+use thiserror::Error;
+
+#[derive(Debug, Error)]
+pub enum Error {
+	#[error(transparent)]
+	Subsystem(#[from] polkadot_subsystem::SubsystemError),
+	#[error(transparent)]
+	OneshotRecv(#[from] futures::channel::oneshot::Canceled),
+	#[error(transparent)]
+	Runtime(#[from] polkadot_subsystem::errors::RuntimeApiError),
+	#[error(transparent)]
+	ValidatorDiscovery(#[from] polkadot_node_subsystem_util::validator_discovery::Error),
+	#[error(transparent)]
+	Util(#[from] polkadot_node_subsystem_util::Error),
+}
+
+pub type Result<T> = std::result::Result<T, Error>;