Request based availability distribution (#2423)

* WIP

* availability distribution, still very wip.

Work on the requesting side of things.

* Some docs on what I intend to do.

* Checkpoint of session cache implementation

as I will likely replace it with something smarter.

* More work, mostly on cache

and getting things to type check.

* Only derive MallocSizeOf and Debug for std.

* availability-distribution: Cache feature complete.

* Sketch out logic in `FetchTask` for actual fetching.

- Compile fixes.
- Cleanup.

* Format cleanup.

* More format fixes.

* Almost feature complete `fetch_task`.

Missing:

- Check for cancel
- Actual querying of peer ids.

* Finish FetchTask so far.

* Directly use AuthorityDiscoveryId in protocol and cache.

* Resolve `AuthorityDiscoveryId` on sending requests.

* Rework fetch_task

- also make it impossible to check the wrong chunk index.
- Export needed function in validator_discovery.

* From<u32> implementation for `ValidatorIndex`.

* Fixes and more integration work.

* Make session cache proper lru cache.

* Use proper lru cache.

* Requester finished.

* ProtocolState -> Requester

Also make sure to not fetch our own chunk.

* Cleanup + fixes.

* Remove unused functions

- FetchTask::is_finished
- SessionCache::fetch_session_info

* availability-distribution responding side.

* Cleanup + Fixes.

* More fixes.

* More fixes.

adder-collator is running!

* Some docs.

* Docs.

* Fix reporting of bad guys.

* Fix tests

* Make all tests compile.

* Fix test.

* Cleanup + get rid of some warnings.

* state -> requester

* Mostly doc fixes.

* Fix test suite.

* Get rid of now redundant message types.

* WIP

* Rob's review remarks.

* Fix test suite.

* core.relay_parent -> leaf for session request.

* Style fix.

* Decrease request timeout.

* Cleanup obsolete errors.

* Metrics + don't fail on non fatal errors.

* requester.rs -> requester/mod.rs

* Panic on invalid BadValidator report.

* Fix indentation.

* Use typed default timeout constant.

* Make channel size 0, as each sender gets one slot anyways.

* Fix incorrect metrics initialization.

* Fix build after merge.

* More fixes.

* Hopefully valid metrics names.

* Better metrics names.

* Some tests that already work.

* Slightly better docs.

* Some more tests.

* Fix network bridge test.

polkadot/node/network/bridge/src/lib.rs

@@ -117,7 +117,7 @@ impl<N, AD> NetworkBridge<N, AD> {
 
 impl<Net, AD, Context> Subsystem<Context> for NetworkBridge<Net, AD>
 	where
-		Net: Network + validator_discovery::Network,
+		Net: Network + validator_discovery::Network + Sync,
 		AD: validator_discovery::AuthorityDiscovery,
 		Context: SubsystemContext<Message=NetworkBridgeMessage>,
 {
@@ -237,7 +237,10 @@ where
 
 			Action::SendRequests(reqs) => {
 				for req in reqs {
-					bridge.network_service.start_request(req);
+					bridge
+						.network_service
+						.start_request(&mut bridge.authority_discovery_service, req)
+						.await;
 				}
 			},
 
@@ -605,7 +608,6 @@ mod tests {
 
 	use polkadot_subsystem::{ActiveLeavesUpdate, FromOverseer, OverseerSignal};
 	use polkadot_subsystem::messages::{
-		AvailabilityDistributionMessage,
 		AvailabilityRecoveryMessage,
 		ApprovalDistributionMessage,
 		BitfieldDistributionMessage,
@@ -624,6 +626,7 @@ mod tests {
 	use polkadot_node_network_protocol::{ObservedRole, request_response::request::Requests};
 
 	use crate::network::{Network, NetworkAction};
+	use crate::validator_discovery::AuthorityDiscovery;
 
 	// The subsystem's view of the network - only supports a single call to `event_stream`.
 	struct TestNetwork {
@@ -663,6 +666,7 @@ mod tests {
 		)
 	}
 
+	#[async_trait]
 	impl Network for TestNetwork {
 		fn event_stream(&mut self) -> BoxStream<'static, NetworkEvent> {
 			self.net_events.lock()
@@ -677,7 +681,7 @@ mod tests {
 			Box::pin((&mut self.action_tx).sink_map_err(Into::into))
 		}
 
-		fn start_request(&self, _: Requests) {
+		async fn start_request<AD: AuthorityDiscovery>(&self, _: &mut AD, _: Requests) {
 		}
 	}
 
@@ -801,13 +805,6 @@ mod tests {
 			) if e == event.focus().expect("could not focus message")
 		);
 
-		assert_matches!(
-			virtual_overseer.recv().await,
-			AllMessages::AvailabilityDistribution(
-				AvailabilityDistributionMessage::NetworkBridgeUpdateV1(e)
-			) if e == event.focus().expect("could not focus message")
-		);
-
 		assert_matches!(
 			virtual_overseer.recv().await,
 			AllMessages::AvailabilityRecovery(
@@ -1527,7 +1524,7 @@ mod tests {
 	fn spread_event_to_subsystems_is_up_to_date() {
 		// Number of subsystems expected to be interested in a network event,
 		// and hence the network event broadcasted to.
-		const EXPECTED_COUNT: usize = 6;
+		const EXPECTED_COUNT: usize = 5;
 
 		let mut cnt = 0_usize;
 		for msg in AllMessages::dispatch_iter(NetworkBridgeEvent::PeerDisconnected(PeerId::random())) {
@@ -1538,7 +1535,7 @@ mod tests {
 				AllMessages::ChainApi(_) => unreachable!("Not interested in network events"),
 				AllMessages::CollatorProtocol(_) => unreachable!("Not interested in network events"),
 				AllMessages::StatementDistribution(_) => { cnt += 1; }
-				AllMessages::AvailabilityDistribution(_) => { cnt += 1; }
+				AllMessages::AvailabilityDistribution(_) => unreachable!("Not interested in network events"),
 				AllMessages::AvailabilityRecovery(_) => { cnt += 1; }
 				AllMessages::BitfieldDistribution(_) => { cnt += 1; }
 				AllMessages::BitfieldSigning(_) => unreachable!("Not interested in network events"),