feat: Speculative Availability

cumulus/client/relay-chain-inprocess-interface/src/lib.rs

@@ -419,6 +419,7 @@ fn build_polkadot_full_node(
 		keep_finalized_for: None,
 		invulnerable_ah_collators: HashSet::new(),
 		collator_protocol_hold_off: None,
+		speculative_availability: false,
 	};
 
 	let (relay_chain_full_node, paranode_req_receiver) = match config.network.network_backend {

polkadot/cli/src/cli.rs

@@ -166,6 +166,10 @@ pub struct RunCmd {
 	///  **Dangerous!** Do not touch unless explicitly advised to.
 	#[arg(long, hide = true)]
 	pub collator_protocol_hold_off: Option<u64>,
+
+	/// Enable speculative availability requests via Prospective Parachains. Defaults to disabled.
+	#[arg(long = "speculative-availability")]
+	pub speculative_availability: bool,
 }
 
 #[allow(missing_docs)]

polkadot/cli/src/command.rs

@@ -292,6 +292,7 @@ where
 				keep_finalized_for: cli.run.keep_finalized_for,
 				invulnerable_ah_collators,
 				collator_protocol_hold_off,
+				speculative_availability: cli.run.speculative_availability,
 			},
 		)
 		.map(|full| full.task_manager)?;

polkadot/node/core/av-store/src/lib.rs

@@ -1232,6 +1232,30 @@ fn process_message(
 				},
 			}
 		},
+		AvailabilityStoreMessage::NoteBackableCandidates {
+			candidate_hashes,
+			num_validators,
+			tx,
+		} => {
+			for candidate_hash in candidate_hashes {
+				let res = note_backable_candidate(
+					&subsystem.db,
+					&subsystem.config,
+					candidate_hash,
+					num_validators,
+					subsystem,
+				);
+
+				match res {
+					Ok(_) => {},
+					Err(e) => {
+						let _ = tx.send(Err(()));
+						return Err(e)
+					},
+				}
+			}
+			let _ = tx.send(Ok(()));
+		},
 	}
 
 	Ok(())
@@ -1405,3 +1429,30 @@ fn prune_all(db: &Arc<dyn Database>, config: &Config, now: Duration) -> Result<(
 	db.write(tx)?;
 	Ok(())
 }
+
+fn note_backable_candidate(
+	db: &Arc<dyn Database>,
+	config: &Config,
+	candidate_hash: CandidateHash,
+	num_validators: usize,
+	subsystem: &AvailabilityStoreSubsystem,
+) -> Result<(), Error> {
+	let mut tx = DBTransaction::new();
+
+	if load_meta(db, config, &candidate_hash)?.is_none() {
+		let now = subsystem.clock.now()?;
+		let meta = CandidateMeta {
+			state: State::Unavailable(now.into()),
+			data_available: false,
+			chunks_stored: bitvec::bitvec![u8, BitOrderLsb0; 0; num_validators],
+		};
+
+		let prune_at = now + KEEP_UNAVAILABLE_FOR;
+
+		write_pruning_key(&mut tx, config, prune_at, &candidate_hash);
+		write_meta(&mut tx, config, &candidate_hash, &meta);
+	}
+
+	db.write(tx)?;
+	Ok(())
+}

polkadot/node/core/provisioner/Cargo.toml

@@ -12,7 +12,6 @@ repository.workspace = true
 workspace = true
 
 [dependencies]
-bitvec = { features = ["alloc"], workspace = true }
 fatality = { workspace = true }
 futures = { workspace = true }
 futures-timer = { workspace = true }