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/availability-recovery/src/tests.rs

@@ -184,7 +184,7 @@ impl TestState {
 					validators: self.validator_public.clone(),
 					discovery_keys: self.validator_authority_id.clone(),
 					// all validators in the same group.
-					validator_groups: vec![(0..self.validators.len()).map(|i| i as ValidatorIndex).collect()],
+					validator_groups: vec![(0..self.validators.len()).map(|i| ValidatorIndex(i as _)).collect()],
 					..Default::default()
 				}))).unwrap();
 			}
@@ -272,10 +272,10 @@ impl TestState {
 						virtual_overseer,
 						AvailabilityRecoveryMessage::NetworkBridgeUpdateV1(
 							NetworkBridgeEvent::PeerMessage(
-								self.validator_peer_id[validator_index as usize].clone(),
+								self.validator_peer_id[validator_index.0 as usize].clone(),
 								protocol_v1::AvailabilityRecoveryMessage::Chunk(
 									request_id,
-									Some(self.chunks[validator_index as usize].clone()),
+									Some(self.chunks[validator_index.0 as usize].clone()),
 								)
 							)
 						)
@@ -317,10 +317,10 @@ impl TestState {
 						virtual_overseer,
 						AvailabilityRecoveryMessage::NetworkBridgeUpdateV1(
 							NetworkBridgeEvent::PeerMessage(
-								self.validator_peer_id[validator_index as usize].clone(),
+								self.validator_peer_id[validator_index.0 as usize].clone(),
 								protocol_v1::AvailabilityRecoveryMessage::Chunk(
 									request_id,
-									Some(self.chunks[validator_index as usize].clone()),
+									Some(self.chunks[validator_index.0 as usize].clone()),
 								)
 							)
 						)
@@ -457,7 +457,7 @@ fn derive_erasure_chunks_with_proofs_and_root(
 		.enumerate()
 		.map(|(index, (proof, chunk))| ErasureChunk {
 			chunk: chunk.to_vec(),
-			index: index as _,
+			index: ValidatorIndex(index as _),
 			proof,
 		})
 		.collect::<Vec<ErasureChunk>>();