'No sync target' logging improvements

ethereum/core/src/main/java/org/hyperledger/besu/ethereum/util/LogUtil.java

@@ -0,0 +1,39 @@
+/*
+ * 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.ethereum.util;
+
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.function.Consumer;
+
+public class LogUtil {
+  static ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor();
+
+  public static void throttledLog(
+      final Consumer<String> logger,
+      final String logMessage,
+      final AtomicBoolean shouldLog,
+      final int logRepeatDelay) {
+
+    if (shouldLog.compareAndSet(true, false)) {
+      logger.accept(logMessage);
+
+      final Runnable runnable = () -> shouldLog.set(true);
+      executor.schedule(runnable, logRepeatDelay, TimeUnit.SECONDS);
+    }
+  }
+}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright ConsenSys AG.
+ * 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
@@ -16,6 +16,7 @@
 
 import static java.util.concurrent.CompletableFuture.completedFuture;
 import static org.hyperledger.besu.ethereum.eth.sync.fastsync.PivotBlockRetriever.MAX_QUERY_RETRIES_PER_PEER;
+import static org.hyperledger.besu.ethereum.util.LogUtil.throttledLog;
 
 import org.hyperledger.besu.ethereum.ProtocolContext;
 import org.hyperledger.besu.ethereum.core.BlockHeader;
@@ -33,6 +34,7 @@
 import java.util.List;
 import java.util.Optional;
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.atomic.AtomicBoolean;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -46,6 +48,10 @@ public class FastSyncTargetManager extends SyncTargetManager {
   private final EthContext ethContext;
   private final MetricsSystem metricsSystem;
   private final FastSyncState fastSyncState;
+  private final AtomicBoolean logDebug = new AtomicBoolean(true);
+  private final AtomicBoolean logInfo = new AtomicBoolean(true);
+  private final int logDebugRepeatDelay = 15;
+  private final int logInfoRepeatDelay = 120;
 
   public FastSyncTargetManager(
       final SynchronizerConfiguration config,
@@ -69,10 +75,21 @@ protected CompletableFuture<Optional<EthPeer>> selectBestAvailableSyncTarget() {
     final BlockHeader pivotBlockHeader = fastSyncState.getPivotBlockHeader().get();
     final EthPeers ethPeers = ethContext.getEthPeers();
     final Optional<EthPeer> maybeBestPeer = ethPeers.bestPeerWithHeightEstimate();
-    if (!maybeBestPeer.isPresent()) {
-      LOG.debug(
-          "No sync target, checking current peers for usefulness: {}",
-          ethContext.getEthPeers().peerCount());
+    if (maybeBestPeer.isEmpty()) {
+      throttledLog(
+          LOG::debug,
+          String.format(
+              "Unable to find sync target. Currently checking %d peers for usefulness. Pivot block: %d",
+              ethContext.getEthPeers().peerCount(), pivotBlockHeader.getNumber()),
+          logDebug,
+          logDebugRepeatDelay);
+      throttledLog(
+          LOG::info,
+          String.format(
+              "Unable to find sync target. Currently checking %d peers for usefulness.",
+              ethContext.getEthPeers().peerCount()),
+          logInfo,
+          logInfoRepeatDelay);
       return completedFuture(Optional.empty());
     } else {
       final EthPeer bestPeer = maybeBestPeer.get();