feat: ForkChoiceNotifications for BlockchainProvider and NoopProvider (#10231)

Co-authored-by: Matthias Seitz <matthias.seitz@outlook.de>

crates/chain-state/src/chain_info.rs

@@ -121,6 +121,16 @@ impl ChainInfoTracker {
             let _ = h.replace(header);
         });
     }
+
+    /// Subscribe to the finalized block.
+    pub fn subscribe_to_finalized_block(&self) -> watch::Receiver<Option<SealedHeader>> {
+        self.inner.finalized_block.subscribe()
+    }
+
+    /// Subscribe to the safe block.
+    pub fn subscribe_to_safe_block(&self) -> watch::Receiver<Option<SealedHeader>> {
+        self.inner.safe_block.subscribe()
+    }
 }
 
 /// Container type for all chain info fields

crates/chain-state/src/notifications.rs

@@ -140,17 +140,20 @@ impl CanonStateNotification {
 
 /// Wrapper around a broadcast receiver that receives fork choice notifications.
 #[derive(Debug, Deref, DerefMut)]
-pub struct ForkChoiceNotifications(broadcast::Receiver<SealedHeader>);
+pub struct ForkChoiceNotifications(pub watch::Receiver<Option<SealedHeader>>);
 
 /// A trait that allows to register to fork choice related events
 /// and get notified when a new fork choice is available.
 pub trait ForkChoiceSubscriptions: Send + Sync {
-    /// Get notified when a new head of the chain is selected.
-    fn subscribe_to_fork_choice(&self) -> ForkChoiceNotifications;
+    /// Get notified when a new safe block of the chain is selected.
+    fn subscribe_to_safe_block(&self) -> ForkChoiceNotifications;
 
-    /// Convenience method to get a stream of the new head of the chain.
+    /// Get notified when a new finalized block of the chain is selected.
+    fn subscribe_to_finalized_block(&self) -> ForkChoiceNotifications;
+
+    /// Convenience method to get a stream of the new safe blocks of the chain.
     fn fork_choice_stream(&self) -> ForkChoiceStream {
-        ForkChoiceStream { st: BroadcastStream::new(self.subscribe_to_fork_choice().0) }
+        ForkChoiceStream { st: WatchStream::new(self.subscribe_to_safe_block().0) }
     }
 }
 
@@ -159,7 +162,7 @@ pub trait ForkChoiceSubscriptions: Send + Sync {
 #[pin_project::pin_project]
 pub struct ForkChoiceStream {
     #[pin]
-    st: BroadcastStream<SealedHeader>,
+    st: WatchStream<Option<SealedHeader>>,
 }
 
 impl Stream for ForkChoiceStream {
@@ -167,14 +170,11 @@ impl Stream for ForkChoiceStream {
 
     fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
         loop {
-            return match ready!(self.as_mut().project().st.poll_next(cx)) {
-                Some(Ok(notification)) => Poll::Ready(Some(notification)),
-                Some(Err(err)) => {
-                    debug!(%err, "finalized header notification stream lagging behind");
-                    continue
-                }
-                None => Poll::Ready(None),
-            };
+            match ready!(self.as_mut().project().st.poll_next(cx)) {
+                Some(Some(notification)) => return Poll::Ready(Some(notification)),
+                Some(None) => continue,
+                None => return Poll::Ready(None),
+            }
         }
     }
 }

crates/storage/provider/src/providers/mod.rs

@@ -12,7 +12,7 @@ use reth_blockchain_tree_api::{
     BlockValidationKind, BlockchainTreeEngine, BlockchainTreeViewer, CanonicalOutcome,
     InsertPayloadOk,
 };
-use reth_chain_state::ChainInfoTracker;
+use reth_chain_state::{ChainInfoTracker, ForkChoiceNotifications, ForkChoiceSubscriptions};
 use reth_chainspec::{ChainInfo, ChainSpec};
 use reth_db_api::{
     database::Database,
@@ -940,6 +940,21 @@ where
     }
 }
 
+impl<DB> ForkChoiceSubscriptions for BlockchainProvider<DB>
+where
+    DB: Send + Sync,
+{
+    fn subscribe_to_safe_block(&self) -> ForkChoiceNotifications {
+        let receiver = self.chain_info.subscribe_to_safe_block();
+        ForkChoiceNotifications(receiver)
+    }
+
+    fn subscribe_to_finalized_block(&self) -> ForkChoiceNotifications {
+        let receiver = self.chain_info.subscribe_to_finalized_block();
+        ForkChoiceNotifications(receiver)
+    }
+}
+
 impl<DB> ChangeSetReader for BlockchainProvider<DB>
 where
     DB: Database,

crates/storage/provider/src/test_utils/noop.rs

@@ -4,7 +4,10 @@ use std::{
     sync::Arc,
 };
 
-use reth_chain_state::{CanonStateNotifications, CanonStateSubscriptions};
+use reth_chain_state::{
+    CanonStateNotifications, CanonStateSubscriptions, ForkChoiceNotifications,
+    ForkChoiceSubscriptions,
+};
 use reth_chainspec::{ChainInfo, ChainSpec, MAINNET};
 use reth_db_api::models::{AccountBeforeTx, StoredBlockBodyIndices};
 use reth_errors::ProviderError;
@@ -21,7 +24,7 @@ use reth_storage_api::StateProofProvider;
 use reth_storage_errors::provider::ProviderResult;
 use reth_trie::{updates::TrieUpdates, AccountProof, HashedPostState};
 use revm::primitives::{BlockEnv, CfgEnvWithHandlerCfg};
-use tokio::sync::broadcast;
+use tokio::sync::{broadcast, watch};
 
 use crate::{
     providers::StaticFileProvider,
@@ -532,3 +535,15 @@ impl CanonStateSubscriptions for NoopProvider {
         broadcast::channel(1).1
     }
 }
+
+impl ForkChoiceSubscriptions for NoopProvider {
+    fn subscribe_to_safe_block(&self) -> ForkChoiceNotifications {
+        let (_, rx) = watch::channel(None);
+        ForkChoiceNotifications(rx)
+    }
+
+    fn subscribe_to_finalized_block(&self) -> ForkChoiceNotifications {
+        let (_, rx) = watch::channel(None);
+        ForkChoiceNotifications(rx)
+    }
+}