post-merge sync and peering fix

besu/src/main/java/org/hyperledger/besu/controller/MergeBesuControllerBuilder.java

@@ -17,6 +17,7 @@
 import org.hyperledger.besu.consensus.merge.MergeContext;
 import org.hyperledger.besu.consensus.merge.MergeProtocolSchedule;
 import org.hyperledger.besu.consensus.merge.PostMergeContext;
+import org.hyperledger.besu.consensus.merge.TransitionBestPeerComparator;
 import org.hyperledger.besu.consensus.merge.blockcreation.MergeCoordinator;
 import org.hyperledger.besu.datatypes.Hash;
 import org.hyperledger.besu.ethereum.ProtocolContext;
@@ -91,13 +92,22 @@ protected EthProtocolManager createEthProtocolManager(
       final List<PeerValidator> peerValidators,
       final Optional<MergePeerFilter> mergePeerFilter) {
 
+    var mergeContext = protocolContext.getConsensusContext(MergeContext.class);
+
+    var mergeBestPeerComparator =
+        new TransitionBestPeerComparator(
+            configOptionsSupplier
+                .get()
+                .getTerminalTotalDifficulty()
+                .map(Difficulty::of)
+                .orElseThrow());
+    ethPeers.setBestChainComparator(mergeBestPeerComparator);
+    mergeContext.observeNewIsPostMergeState(mergeBestPeerComparator);
+
     if (mergePeerFilter.isPresent()) {
-      protocolContext
-          .getConsensusContext(MergeContext.class)
-          .observeNewIsPostMergeState(mergePeerFilter.get());
-      protocolContext
-          .getConsensusContext(MergeContext.class)
-          .addNewForkchoiceMessageListener(mergePeerFilter.get());
+
+      mergeContext.observeNewIsPostMergeState(mergePeerFilter.get());
+      mergeContext.addNewForkchoiceMessageListener(mergePeerFilter.get());
     }
 
     EthProtocolManager ethProtocolManager =

besu/src/main/java/org/hyperledger/besu/controller/TransitionBesuControllerBuilder.java

@@ -31,7 +31,13 @@
 import org.hyperledger.besu.ethereum.core.MiningParameters;
 import org.hyperledger.besu.ethereum.core.PrivacyParameters;
 import org.hyperledger.besu.ethereum.eth.EthProtocolConfiguration;
+import org.hyperledger.besu.ethereum.eth.manager.EthContext;
+import org.hyperledger.besu.ethereum.eth.manager.EthMessages;
+import org.hyperledger.besu.ethereum.eth.manager.EthPeers;
 import org.hyperledger.besu.ethereum.eth.manager.EthProtocolManager;
+import org.hyperledger.besu.ethereum.eth.manager.EthScheduler;
+import org.hyperledger.besu.ethereum.eth.manager.MergePeerFilter;
+import org.hyperledger.besu.ethereum.eth.peervalidation.PeerValidator;
 import org.hyperledger.besu.ethereum.eth.sync.SynchronizerConfiguration;
 import org.hyperledger.besu.ethereum.eth.sync.backwardsync.BackwardSyncContext;
 import org.hyperledger.besu.ethereum.eth.sync.state.SyncState;
@@ -119,6 +125,31 @@ protected MiningCoordinator createMiningCoordinator(
     return composedCoordinator;
   }
 
+  @Override
+  protected EthProtocolManager createEthProtocolManager(
+      final ProtocolContext protocolContext,
+      final boolean fastSyncEnabled,
+      final TransactionPool transactionPool,
+      final EthProtocolConfiguration ethereumWireProtocolConfiguration,
+      final EthPeers ethPeers,
+      final EthContext ethContext,
+      final EthMessages ethMessages,
+      final EthScheduler scheduler,
+      final List<PeerValidator> peerValidators,
+      final Optional<MergePeerFilter> mergePeerFilter) {
+    return mergeBesuControllerBuilder.createEthProtocolManager(
+        protocolContext,
+        fastSyncEnabled,
+        transactionPool,
+        ethereumWireProtocolConfiguration,
+        ethPeers,
+        ethContext,
+        ethMessages,
+        scheduler,
+        peerValidators,
+        mergePeerFilter);
+  }
+
   @Override
   protected ProtocolSchedule createProtocolSchedule() {
     return new TransitionProtocolSchedule(

consensus/merge/src/main/java/org/hyperledger/besu/consensus/merge/TransitionBestPeerComparator.java

@@ -0,0 +1,69 @@
+/*
+ * Copyright Hyperledger Besu Contributors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package org.hyperledger.besu.consensus.merge;
+
+import static org.hyperledger.besu.ethereum.eth.manager.EthPeers.CHAIN_HEIGHT;
+
+import org.hyperledger.besu.ethereum.core.Difficulty;
+import org.hyperledger.besu.ethereum.eth.manager.EthPeer;
+
+import java.math.BigInteger;
+import java.util.Comparator;
+import java.util.Optional;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.BiFunction;
+
+public class TransitionBestPeerComparator implements Comparator<EthPeer>, MergeStateHandler {
+
+  private static final AtomicReference<Difficulty> terminalTotalDifficulty =
+      new AtomicReference<>();
+
+  static final BiFunction<EthPeer, Difficulty, BigInteger> distanceFromTTD =
+      (a, ttd) ->
+          a.chainState()
+              .getEstimatedTotalDifficulty()
+              .getAsBigInteger()
+              .subtract(ttd.getAsBigInteger())
+              .abs()
+              .negate();
+
+  public static final Comparator<EthPeer> EXACT_DIFFICULTY =
+      (a, b) -> {
+        var ttd = terminalTotalDifficulty.get();
+        var aDelta = distanceFromTTD.apply(a, ttd);
+        var bDelta = distanceFromTTD.apply(b, ttd);
+        return aDelta.compareTo(bDelta);
+      };
+
+  public static final Comparator<EthPeer> BEST_MERGE_CHAIN =
+      EXACT_DIFFICULTY.thenComparing(CHAIN_HEIGHT);
+
+  public TransitionBestPeerComparator(final Difficulty configuredTerminalTotalDifficulty) {
+    terminalTotalDifficulty.set(configuredTerminalTotalDifficulty);
+  }
+
+  @Override
+  public void mergeStateChanged(
+      final boolean isPoS, final Optional<Difficulty> difficultyStoppedAt) {
+    if (isPoS && difficultyStoppedAt.isPresent()) {
+      terminalTotalDifficulty.set(difficultyStoppedAt.get());
+    }
+  }
+
+  @Override
+  public int compare(final EthPeer o1, final EthPeer o2) {
+    return BEST_MERGE_CHAIN.compare(o1, o2);
+  }
+}

consensus/merge/src/test/java/org/hyperledger/besu/consensus/merge/TransitionBestPeerComparatorTest.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright Hyperledger Besu Contributors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
+ * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package org.hyperledger.besu.consensus.merge;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.when;
+
+import org.hyperledger.besu.ethereum.core.Difficulty;
+import org.hyperledger.besu.ethereum.eth.manager.EthPeer;
+
+import java.util.Optional;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Answers;
+import org.mockito.Mock;
+import org.mockito.junit.MockitoJUnitRunner;
+
+@RunWith(MockitoJUnitRunner.class)
+public class TransitionBestPeerComparatorTest {
+
+  @Mock(answer = Answers.RETURNS_DEEP_STUBS)
+  EthPeer a;
+
+  @Mock(answer = Answers.RETURNS_DEEP_STUBS)
+  EthPeer b;
+
+  @Test
+  public void assertDistanceFromTTDPrecedence() {
+    var comparator = new TransitionBestPeerComparator(Difficulty.of(5000));
+    when(a.chainState().getEstimatedTotalDifficulty()).thenReturn(Difficulty.of(5002));
+    when(b.chainState().getEstimatedTotalDifficulty()).thenReturn(Difficulty.of(4995));
+    // a has less distance from TTD:
+    assertThat(comparator.compare(a, b)).isEqualTo(1);
+    when(b.chainState().getEstimatedTotalDifficulty()).thenReturn(Difficulty.of(5001));
+    // b has less distance from TTD:
+    assertThat(comparator.compare(a, b)).isEqualTo(-1);
+    when(b.chainState().getEstimatedTotalDifficulty()).thenReturn(Difficulty.of(5002));
+    // a and b are equi-distant
+    assertThat(comparator.compare(a, b)).isEqualTo(0);
+  }
+
+  @Test
+  public void assertHandlesNewTTD() {
+    var comparator = new TransitionBestPeerComparator(Difficulty.of(5000));
+    when(a.chainState().getEstimatedTotalDifficulty()).thenReturn(Difficulty.of(5002));
+    when(b.chainState().getEstimatedTotalDifficulty()).thenReturn(Difficulty.of(4999));
+    assertThat(comparator.compare(a, b)).isEqualTo(-1);
+
+    // update TTD with actual value
+    comparator.mergeStateChanged(true, Optional.of(Difficulty.of(5002)));
+    assertThat(comparator.compare(a, b)).isEqualTo(1);
+  }
+}

ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/manager/EthPeers.java

@@ -36,14 +36,19 @@
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 public class EthPeers {
+  private static final Logger LOG = LoggerFactory.getLogger(EthPeers.class);
   public static final Comparator<EthPeer> TOTAL_DIFFICULTY =
       Comparator.comparing(((final EthPeer p) -> p.chainState().getEstimatedTotalDifficulty()));
 
   public static final Comparator<EthPeer> CHAIN_HEIGHT =
       Comparator.comparing(((final EthPeer p) -> p.chainState().getEstimatedHeight()));
 
-  public static final Comparator<EthPeer> BEST_CHAIN = TOTAL_DIFFICULTY.thenComparing(CHAIN_HEIGHT);
+  public static final Comparator<EthPeer> HEAVIEST_CHAIN =
+      TOTAL_DIFFICULTY.thenComparing(CHAIN_HEIGHT);
 
   public static final Comparator<EthPeer> LEAST_TO_MOST_BUSY =
       Comparator.comparing(EthPeer::outstandingRequests)
@@ -59,6 +64,8 @@ public class EthPeers {
   private final Subscribers<DisconnectCallback> disconnectCallbacks = Subscribers.create();
   private final Collection<PendingPeerRequest> pendingRequests = new CopyOnWriteArrayList<>();
 
+  private Comparator<EthPeer> bestPeerComparator;
+
   public EthPeers(
       final String protocolName,
       final Clock clock,
@@ -80,6 +87,7 @@ public EthPeers(
     this.permissioningProviders = permissioningProviders;
     this.maxPeers = maxPeers;
     this.maxMessageSize = maxMessageSize;
+    this.bestPeerComparator = HEAVIEST_CHAIN;
     metricsSystem.createIntegerGauge(
         BesuMetricCategory.PEERS,
         "pending_peer_requests_current",
@@ -186,11 +194,11 @@ public Stream<EthPeer> streamAvailablePeers() {
   }
 
   public Stream<EthPeer> streamBestPeers() {
-    return streamAvailablePeers().sorted(BEST_CHAIN.reversed());
+    return streamAvailablePeers().sorted(getBestChainComparator().reversed());
   }
 
   public Optional<EthPeer> bestPeer() {
-    return streamAvailablePeers().max(BEST_CHAIN);
+    return streamAvailablePeers().max(getBestChainComparator());
   }
 
   public Optional<EthPeer> bestPeerWithHeightEstimate() {
@@ -199,7 +207,16 @@ public Optional<EthPeer> bestPeerWithHeightEstimate() {
   }
 
   public Optional<EthPeer> bestPeerMatchingCriteria(final Predicate<EthPeer> matchesCriteria) {
-    return streamAvailablePeers().filter(matchesCriteria).max(BEST_CHAIN);
+    return streamAvailablePeers().filter(matchesCriteria).max(getBestChainComparator());
+  }
+
+  public void setBestChainComparator(final Comparator<EthPeer> comparator) {
+    LOG.info("Updating the default best peer comparator");
+    bestPeerComparator = comparator;
+  }
+
+  public Comparator<EthPeer> getBestChainComparator() {
+    return bestPeerComparator;
   }
 
   @FunctionalInterface

ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/sync/DefaultSynchronizer.java

@@ -228,9 +228,13 @@ private CompletableFuture<Void> handleSyncResult(final FastSyncState result) {
         result.getPivotBlockNumber().getAsLong());
     pivotBlockSelector.close();
     syncState.markInitialSyncPhaseAsDone();
-    return terminationCondition.shouldContinueDownload()
-        ? startFullSync()
-        : CompletableFuture.completedFuture(null);
+
+    if (terminationCondition.shouldContinueDownload()) {
+      return startFullSync();
+    } else {
+      syncState.setReachedTerminalDifficulty(true);
+      return CompletableFuture.completedFuture(null);
+    }
   }
 
   private CompletableFuture<Void> startFullSync() {

ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/sync/backwardsync/BackwardSyncContext.java

@@ -265,6 +265,10 @@ public BlockValidator getBlockValidatorForBlock(final Block block) {
   }
 
   public boolean isReady() {
+    LOG.debug(
+        "checking if BWS is ready: ttd reached {}, initial sync done {}",
+        syncState.hasReachedTerminalDifficulty().orElse(Boolean.FALSE),
+        syncState.isInitialSyncPhaseDone());
     return syncState.hasReachedTerminalDifficulty().orElse(Boolean.FALSE)
         && syncState.isInitialSyncPhaseDone();
   }

ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/sync/fastsync/FastSyncActions.java

@@ -176,6 +176,11 @@ private long countPeersThatCanDeterminePivotBlock() {
   }
 
   private boolean canPeerDeterminePivotBlock(final EthPeer peer) {
+    LOG.debug(
+        "peer {} hasEstimatedHeight {} isFullyValidated? {}",
+        peer.getShortNodeId(),
+        peer.chainState().hasEstimatedHeight(),
+        peer.isFullyValidated());
     return peer.chainState().hasEstimatedHeight() && peer.isFullyValidated();
   }
 

ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/sync/fastsync/FastSyncTargetManager.java

@@ -76,8 +76,10 @@ protected CompletableFuture<Optional<EthPeer>> selectBestAvailableSyncTarget() {
       final EthPeer bestPeer = maybeBestPeer.get();
       if (bestPeer.chainState().getEstimatedHeight() < pivotBlockHeader.getNumber()) {
         LOG.info(
-            "No sync target with sufficient chain height, waiting for peers: {}",
-            ethContext.getEthPeers().peerCount());
+            "Best peer {} has chain height {} below pivotBlock height {}",
+            maybeBestPeer.map(EthPeer::getShortNodeId).orElse("none"),
+            maybeBestPeer.map(p -> p.chainState().getEstimatedHeight()).orElse(-1L),
+            pivotBlockHeader.getNumber());
         return completedFuture(Optional.empty());
       } else {
         return confirmPivotBlockHeader(bestPeer);

ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/sync/fullsync/BetterSyncTargetEvaluator.java

@@ -40,7 +40,7 @@ public boolean shouldSwitchSyncTarget(final EthPeer currentSyncTarget) {
     return maybeBestPeer
         .map(
             bestPeer -> {
-              if (EthPeers.BEST_CHAIN.compare(bestPeer, currentSyncTarget) <= 0) {
+              if (ethPeers.getBestChainComparator().compare(bestPeer, currentSyncTarget) <= 0) {
                 // Our current target is better or equal to the best peer
                 return false;
               }

ethereum/eth/src/test/java/org/hyperledger/besu/ethereum/eth/manager/EthPeersTest.java

@@ -69,10 +69,10 @@ public void comparesPeersWithHeightAndTd() {
     assertThat(EthPeers.CHAIN_HEIGHT.compare(peerA, peerB)).isGreaterThan(0);
     assertThat(EthPeers.TOTAL_DIFFICULTY.compare(peerA, peerB)).isLessThan(0);
 
-    assertThat(EthPeers.BEST_CHAIN.compare(peerA, peerB)).isLessThan(0);
-    assertThat(EthPeers.BEST_CHAIN.compare(peerB, peerA)).isGreaterThan(0);
-    assertThat(EthPeers.BEST_CHAIN.compare(peerA, peerA)).isEqualTo(0);
-    assertThat(EthPeers.BEST_CHAIN.compare(peerB, peerB)).isEqualTo(0);
+    assertThat(EthPeers.HEAVIEST_CHAIN.compare(peerA, peerB)).isLessThan(0);
+    assertThat(EthPeers.HEAVIEST_CHAIN.compare(peerB, peerA)).isGreaterThan(0);
+    assertThat(EthPeers.HEAVIEST_CHAIN.compare(peerA, peerA)).isEqualTo(0);
+    assertThat(EthPeers.HEAVIEST_CHAIN.compare(peerB, peerB)).isEqualTo(0);
 
     assertThat(ethProtocolManager.ethContext().getEthPeers().bestPeer()).contains(peerB);
     assertThat(ethProtocolManager.ethContext().getEthPeers().bestPeerWithHeightEstimate())
@@ -97,10 +97,10 @@ public void comparesPeersWithTdAndNoHeight() {
     assertThat(EthPeers.CHAIN_HEIGHT.compare(peerA, peerB)).isEqualTo(0);
     assertThat(EthPeers.TOTAL_DIFFICULTY.compare(peerA, peerB)).isGreaterThan(0);
 
-    assertThat(EthPeers.BEST_CHAIN.compare(peerA, peerB)).isGreaterThan(0);
-    assertThat(EthPeers.BEST_CHAIN.compare(peerB, peerA)).isLessThan(0);
-    assertThat(EthPeers.BEST_CHAIN.compare(peerA, peerA)).isEqualTo(0);
-    assertThat(EthPeers.BEST_CHAIN.compare(peerB, peerB)).isEqualTo(0);
+    assertThat(EthPeers.HEAVIEST_CHAIN.compare(peerA, peerB)).isGreaterThan(0);
+    assertThat(EthPeers.HEAVIEST_CHAIN.compare(peerB, peerA)).isLessThan(0);
+    assertThat(EthPeers.HEAVIEST_CHAIN.compare(peerA, peerA)).isEqualTo(0);
+    assertThat(EthPeers.HEAVIEST_CHAIN.compare(peerB, peerB)).isEqualTo(0);
 
     assertThat(ethProtocolManager.ethContext().getEthPeers().bestPeer()).contains(peerA);
     assertThat(ethProtocolManager.ethContext().getEthPeers().bestPeerWithHeightEstimate())