Add HeadTracker struct

beacon_node/beacon_chain/src/beacon_chain.rs

@@ -3,6 +3,7 @@ use crate::errors::{BeaconChainError as Error, BlockProductionError};
 use crate::eth1_chain::{Eth1Chain, Eth1ChainBackend};
 use crate::events::{EventHandler, EventKind};
 use crate::fork_choice::{Error as ForkChoiceError, ForkChoice};
+use crate::head_tracker::HeadTracker;
 use crate::metrics;
 use crate::persisted_beacon_chain::{PersistedBeaconChain, BEACON_CHAIN_DB_KEY};
 use lmd_ghost::LmdGhost;
@@ -126,6 +127,8 @@ pub struct BeaconChain<T: BeaconChainTypes> {
     pub fork_choice: ForkChoice<T>,
     /// A handler for events generated by the beacon chain.
     pub event_handler: T::EventHandler,
+    /// Used to track the heads of the beacon chain.
+    pub(crate) head_tracker: HeadTracker,
     /// Logging to CLI, etc.
     pub(crate) log: Logger,
 }
@@ -141,6 +144,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
             canonical_head: self.canonical_head.read().clone(),
             op_pool: PersistedOperationPool::from_operation_pool(&self.op_pool),
             genesis_block_root: self.genesis_block_root,
+            ssz_head_tracker: self.head_tracker.to_ssz_container(),
         };
 
         let key = Hash256::from_slice(&BEACON_CHAIN_DB_KEY.as_bytes());
@@ -1219,6 +1223,8 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
 
         metrics::stop_timer(db_write_timer);
 
+        self.head_tracker.register_block(block_root, &block);
+
         let fork_choice_register_timer =
             metrics::start_timer(&metrics::BLOCK_PROCESSING_FORK_CHOICE_REGISTER);