Separate out the synchronous logic from consensus (#558)

Author: timorleph

Cargo.lock

@@ -1,6 +1,6 @@
 [package]
 name = "aleph-bft"
-version = "0.45.3"
+version = "0.45.4"
 edition = "2021"
 authors = ["Cardinal Cryptography"]
 categories = ["algorithms", "data-structures", "cryptography", "database"]

consensus/Cargo.toml

@@ -0,0 +1,221 @@
+use crate::{
+    alerts::{Alert, ForkingNotification},
+    collection::Salt,
+    consensus::LOG_TARGET,
+    dag::{Dag, DagResult, DagStatus, DagUnit, Request as ReconstructionRequest},
+    dissemination::{Addressed, DisseminationMessage, Responder, TaskManager, TaskManagerStatus},
+    extension::Ordering,
+    units::{UncheckedSignedUnit, Unit, UnitStore, UnitStoreStatus, Validator},
+    Data, DelayConfig, Hasher, MultiKeychain, NodeIndex, UnitFinalizationHandler,
+};
+use log::{debug, trace};
+use std::{
+    cmp::max,
+    fmt::{Display, Formatter, Result as FmtResult},
+    time::Duration,
+};
+
+/// The main logic of the consensus, minus all the asynchronous components.
+pub struct Consensus<UFH, MK>
+where
+    UFH: UnitFinalizationHandler,
+    MK: MultiKeychain,
+{
+    store: UnitStore<DagUnit<UFH::Hasher, UFH::Data, MK>>,
+    dag: Dag<UFH::Hasher, UFH::Data, MK>,
+    responder: Responder<UFH::Hasher, UFH::Data, MK>,
+    ordering: Ordering<MK, UFH>,
+    task_manager: TaskManager<UFH::Hasher>,
+}
+
+/// The status of the consensus, for logging purposes.
+pub struct Status<H: Hasher> {
+    task_manager_status: TaskManagerStatus<H>,
+    dag_status: DagStatus,
+    store_status: UnitStoreStatus,
+}
+
+impl<H: Hasher> Status<H> {
+    fn short_report(&self) -> String {
+        let rounds_behind = max(self.dag_status.top_round(), self.store_status.top_round())
+            - self.store_status.top_round();
+        match rounds_behind {
+            (0..=2) => "healthy".to_string(),
+            (3..) => format!("behind by {rounds_behind} rounds"),
+        }
+    }
+}
+
+impl<H: Hasher> Display for Status<H> {
+    fn fmt(&self, f: &mut Formatter) -> FmtResult {
+        write!(f, "{}", self.short_report())?;
+        write!(f, ";reconstructed DAG: {}", self.store_status)?;
+        write!(f, ";additional information: {}", self.dag_status)?;
+        write!(f, ";task manager: {}", self.task_manager_status)?;
+        Ok(())
+    }
+}
+
+type AddressedDisseminationMessage<H, D, MK> = Addressed<DisseminationMessage<H, D, MK>>;
+
+/// The result of some operation within the consensus, requiring either other components should get
+/// informed about it, or messages should be sent to the network.
+pub struct ConsensusResult<H: Hasher, D: Data, MK: MultiKeychain> {
+    /// Units that should be sent for backup saving.
+    pub units: Vec<DagUnit<H, D, MK>>,
+    /// Alerts that should be sent to the alerting component.
+    pub alerts: Vec<Alert<H, D, MK::Signature>>,
+    /// Messages that should be sent to other committee members.
+    pub messages: Vec<AddressedDisseminationMessage<H, D, MK::Signature>>,
+}
+
+impl<H: Hasher, D: Data, MK: MultiKeychain> ConsensusResult<H, D, MK> {
+    fn noop() -> Self {
+        ConsensusResult {
+            units: Vec::new(),
+            alerts: Vec::new(),
+            messages: Vec::new(),
+        }
+    }
+}
+
+impl<UFH, MK> Consensus<UFH, MK>
+where
+    UFH: UnitFinalizationHandler,
+    MK: MultiKeychain,
+{
+    /// Create a new Consensus.
+    pub fn new(
+        keychain: MK,
+        validator: Validator<MK>,
+        finalization_handler: UFH,
+        delay_config: DelayConfig,
+    ) -> Self {
+        let n_members = keychain.node_count();
+        let index = keychain.index();
+        Consensus {
+            store: UnitStore::new(n_members),
+            dag: Dag::new(validator),
+            responder: Responder::new(keychain),
+            ordering: Ordering::new(finalization_handler),
+            task_manager: TaskManager::new(index, n_members, delay_config),
+        }
+    }
+
+    fn handle_dag_result(
+        &mut self,
+        result: DagResult<UFH::Hasher, UFH::Data, MK>,
+    ) -> ConsensusResult<UFH::Hasher, UFH::Data, MK> {
+        let DagResult {
+            units,
+            alerts,
+            requests,
+        } = result;
+        for request in requests {
+            self.task_manager.add_request(request);
+        }
+        let messages = self.trigger_tasks();
+        ConsensusResult {
+            units,
+            alerts,
+            messages,
+        }
+    }
+
+    /// Process a unit received (usually) from the network.
+    pub fn process_incoming_unit(
+        &mut self,
+        unit: UncheckedSignedUnit<UFH::Hasher, UFH::Data, MK::Signature>,
+    ) -> ConsensusResult<UFH::Hasher, UFH::Data, MK> {
+        let result = self.dag.add_unit(unit, &self.store);
+        self.handle_dag_result(result)
+    }
+
+    /// Process a request received from the network.
+    pub fn process_request(
+        &mut self,
+        request: ReconstructionRequest<UFH::Hasher>,
+        node_id: NodeIndex,
+    ) -> Option<AddressedDisseminationMessage<UFH::Hasher, UFH::Data, MK::Signature>> {
+        match self.responder.handle_request(request, &self.store) {
+            Ok(response) => Some(Addressed::addressed_to(response.into(), node_id)),
+            Err(err) => {
+                debug!(target: LOG_TARGET, "Not answering request from node {:?}: {}.", node_id, err);
+                None
+            }
+        }
+    }
+
+    /// Process a parents response.
+    pub fn process_parents(
+        &mut self,
+        u_hash: <UFH::Hasher as Hasher>::Hash,
+        parents: Vec<UncheckedSignedUnit<UFH::Hasher, UFH::Data, MK::Signature>>,
+    ) -> ConsensusResult<UFH::Hasher, UFH::Data, MK> {
+        if self.store.unit(&u_hash).is_some() {
+            trace!(target: LOG_TARGET, "We got parents response but already imported the unit.");
+            return ConsensusResult::noop();
+        }
+        let result = self.dag.add_parents(u_hash, parents, &self.store);
+        self.handle_dag_result(result)
+    }
+
+    /// Process a newest unit request.
+    pub fn process_newest_unit_request(
+        &mut self,
+        salt: Salt,
+        node_id: NodeIndex,
+    ) -> AddressedDisseminationMessage<UFH::Hasher, UFH::Data, MK::Signature> {
+        Addressed::addressed_to(
+            self.responder
+                .handle_newest_unit_request(node_id, salt, &self.store)
+                .into(),
+            node_id,
+        )
+    }
+
+    /// Process a forking notification.
+    pub fn process_forking_notification(
+        &mut self,
+        notification: ForkingNotification<UFH::Hasher, UFH::Data, MK::Signature>,
+    ) -> ConsensusResult<UFH::Hasher, UFH::Data, MK> {
+        let result = self
+            .dag
+            .process_forking_notification(notification, &self.store);
+        self.handle_dag_result(result)
+    }
+
+    /// What to do once a unit has been securely backed up on disk.
+    pub fn on_unit_backup_saved(
+        &mut self,
+        unit: DagUnit<UFH::Hasher, UFH::Data, MK>,
+    ) -> Option<AddressedDisseminationMessage<UFH::Hasher, UFH::Data, MK::Signature>> {
+        let unit_hash = unit.hash();
+        self.store.insert(unit.clone());
+        self.dag.finished_processing(&unit_hash);
+        self.ordering.add_unit(unit.clone());
+        self.task_manager.add_unit(&unit)
+    }
+
+    /// When should `trigger_tasks` be called next.
+    pub fn next_tick(&self) -> Duration {
+        self.task_manager.next_tick()
+    }
+
+    /// Trigger all the ready tasks and get all the messages that should be sent now.
+    pub fn trigger_tasks(
+        &mut self,
+    ) -> Vec<AddressedDisseminationMessage<UFH::Hasher, UFH::Data, MK::Signature>> {
+        self.task_manager
+            .trigger_tasks(&self.store, self.dag.processing_units())
+    }
+
+    /// The status of the consensus handler, for logging purposes.
+    pub fn status(&self) -> Status<UFH::Hasher> {
+        Status {
+            dag_status: self.dag.status(),
+            store_status: self.store.status(),
+            task_manager_status: self.task_manager.status(),
+        }
+    }
+}

consensus/src/consensus/handler.rs

@@ -2,7 +2,10 @@ use crate::{
     alerts::{Handler as AlertHandler, Service as AlertService, IO as AlertIO},
     backup::{BackupLoader, BackupSaver},
     collection::initial_unit_collection,
-    consensus::service::{Config as ServiceConfig, Service},
+    consensus::{
+        handler::Consensus,
+        service::{Service, IO as ConsensusIO},
+    },
     creation, handle_task_termination,
     interface::LocalIO,
     network::{Hub as NetworkHub, NetworkData},
@@ -16,6 +19,7 @@ use futures::{
 };
 use log::{debug, error, info};
 
+mod handler;
 mod service;
 
 const LOG_TARGET: &str = "AlephBFT-consensus";
@@ -185,13 +189,16 @@ pub async fn run_session<
     pin_mut!(starting_round_handle);
     debug!(target: LOG_TARGET, "Initial unit collection spawned.");
 
-    //TODO: just put the Service here
     debug!(target: LOG_TARGET, "Spawning consensus service.");
+    let consensus = Consensus::new(
+        keychain.clone(),
+        validator.clone(),
+        finalization_handler,
+        config.delay_config().clone(),
+    );
     let service_handle = spawn_handle
         .spawn_essential("consensus/service", {
-            let service_config = ServiceConfig {
-                delay_config: config.delay_config().clone(),
-                finalization_handler,
+            let consensus_io = ConsensusIO {
                 backup_units_for_saver,
                 backup_units_from_saver,
                 alerts_for_alerter,
@@ -203,9 +210,7 @@ pub async fn run_session<
                 new_units_from_creator,
             };
             let service_terminator = terminator.add_offspring_connection("service");
-            let validator = validator.clone();
-            let keychain = keychain.clone();
-            let service = Service::new(service_config, keychain, validator);
+            let service = Service::new(consensus, consensus_io);
 
             async move { service.run(loaded_units, service_terminator).await }
         })