give polkadot control over round proposer based on random seed

polkadot/api/src/lib.rs

@@ -31,9 +31,6 @@ extern crate substrate_state_machine as state_machine;
 #[macro_use]
 extern crate error_chain;
 
-#[macro_use]
-extern crate log;
-
 #[cfg(test)]
 extern crate substrate_keyring as keyring;
 
@@ -42,7 +39,7 @@ use client::Client;
 use polkadot_executor::Executor as LocalDispatch;
 use substrate_executor::{NativeExecutionDispatch, NativeExecutor};
 use state_machine::OverlayedChanges;
-use primitives::{AccountId, BlockId, Index, SessionKey, Timestamp};
+use primitives::{AccountId, BlockId, Hash, Index, SessionKey, Timestamp};
 use primitives::parachain::DutyRoster;
 use runtime::{Block, Header, UncheckedExtrinsic, Extrinsic, Call, TimestampCall};
 
@@ -126,6 +123,9 @@ pub trait PolkadotApi {
  /// Get validators at a given block.
  fn validators(&self, at: &Self::CheckedBlockId) -> Result<Vec<AccountId>>;
 
+ /// Get the value of the randomness beacon at a given block.
+ fn random_seed(&self, at: &Self::CheckedBlockId) -> Result<Hash>;
+
  /// Get the authority duty roster at a block.
  fn duty_roster(&self, at: &Self::CheckedBlockId) -> Result<DutyRoster>;
 
@@ -191,6 +191,10 @@ impl<B: Backend> PolkadotApi for Client<B, NativeExecutor<LocalDispatch>>
  with_runtime!(self, at, ::runtime::Session::validators)
  }
 
+ fn random_seed(&self, at: &CheckedId) -> Result<Hash> {
+ with_runtime!(self, at, ::runtime::System::random_seed)
+ }
+
  fn duty_roster(&self, at: &CheckedId) -> Result<DutyRoster> {
  // duty roster can only be queried at the start of a block,
  // so we create a dummy.

polkadot/consensus/src/lib.rs

@@ -495,6 +495,7 @@ impl<C: PolkadotApi, N: Network> bft::ProposerFactory for ProposerFactory<C, N>
 
  let checked_id = self.client.check_id(BlockId::Hash(parent_hash))?;
  let duty_roster = self.client.duty_roster(&checked_id)?;
+ let random_seed = self.client.random_seed(&checked_id)?;
 
  let group_info = make_group_info(duty_roster, authorities)?;
  let table = Arc::new(SharedTable::new(group_info, sign_with.clone(), parent_hash));
@@ -510,6 +511,7 @@ impl<C: PolkadotApi, N: Network> bft::ProposerFactory for ProposerFactory<C, N>
  parent_hash,
  parent_number: parent_header.number,
  parent_id: checked_id,
+ random_seed,
  local_key: sign_with,
  client: self.client.clone(),
  transaction_pool: self.transaction_pool.clone(),
@@ -533,6 +535,7 @@ pub struct Proposer<C: PolkadotApi, R> {
  parent_hash: HeaderHash,
  parent_number: BlockNumber,
  parent_id: C::CheckedBlockId,
+ random_seed: Hash,
  client: Arc<C>,
  local_key: Arc<ed25519::Pair>,
  transaction_pool: Arc<Mutex<TransactionPool>>,
@@ -625,6 +628,16 @@ impl<C: PolkadotApi, R: TableRouter> bft::Proposer for Proposer<C, R> {
  Box::new(self.delay.clone().map_err(Error::from).and_then(move |_| evaluated))
  }
 
+ fn round_proposer(&self, round_number: usize, authorities: &[AuthorityId]) -> AuthorityId {
+ use primitives::uint::U256;
+
+ let len: U256 = authorities.len().into();
+ let offset = U256::from_big_endian(&self.random_seed.0) % len;
+ let offset = offset.low_u64() as usize + round_number;
+
+ authorities[offset % authorities.len()].clone()
+ }
+
  fn import_misbehavior(&self, misbehavior: Vec<(AuthorityId, bft::Misbehavior)>) {
  use bft::generic::Misbehavior as GenericMisbehavior;
  use primitives::bft::{MisbehaviorKind, MisbehaviorReport};

substrate/bft/src/lib.rs

@@ -133,11 +133,16 @@ pub trait Proposer {
 
  /// Create a proposal.
  fn propose(&self) -> Self::Create;
+
  /// Evaluate proposal. True means valid.
- // TODO: change this to a future.
  fn evaluate(&self, proposal: &Block) -> Self::Evaluate;
+
  /// Import witnessed misbehavior.
  fn import_misbehavior(&self, misbehavior: Vec<(AuthorityId, Misbehavior)>);
+
+ /// Determine the proposer for a given round. This should be a deterministic function
+ /// with consistent results across all authorities.
+ fn round_proposer(&self, round_number: usize, authorities: &[AuthorityId]) -> AuthorityId;
 }
 
 /// Block import trait.
@@ -649,6 +654,10 @@ mod tests {
  }
 
  fn import_misbehavior(&self, _misbehavior: Vec<(AuthorityId, Misbehavior)>) {}
+
+ fn round_proposer(&self, round_number: usize, authorities: &[AuthorityId]) -> AuthorityId {
+ authorities[round_number % authorities.len()].clone()
+ }
  }
 
  fn make_service(client: FakeClient)