feat: FastSync now stops on failure instead of falling back to FullSync (#974)

* feat: FastSync now stops on failure instead of falling back to FullSync

* feat: exiting on FastSync failed

* feat: FastSync continues on FullSync when no errors happened

Signed-off-by: Alexandre PARIS-VERGNE <alexpv14@gmail.com>

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

@@ -126,7 +126,17 @@ public class DefaultSynchronizer<C> implements Synchronizer {
       LOG.info("Starting synchronizer.");
       blockPropagationManager.start();
       if (fastSyncDownloader.isPresent()) {
-        fastSyncDownloader.get().start().whenComplete(this::handleFastSyncResult);
+        fastSyncDownloader
+            .get()
+            .start()
+            .whenComplete(this::handleFastSyncResult)
+            .exceptionally(
+                ex -> {
+                  LOG.warn("Exiting FastSync process");
+                  System.exit(0);
+                  return null;
+                });
+
       } else {
         startFullSync();
       }
@@ -157,20 +167,20 @@ public class DefaultSynchronizer<C> implements Synchronizer {
       // We've been shutdown which will have triggered the fast sync future to complete
       return;
     }
+    fastSyncDownloader.ifPresent(FastSyncDownloader::deleteFastSyncState);
     final Throwable rootCause = ExceptionUtils.rootCause(error);
     if (rootCause instanceof FastSyncException) {
       LOG.error(
-          "Fast sync failed ({}), switching to full sync.",
-          ((FastSyncException) rootCause).getError());
+          "Fast sync failed ({}), please try again.", ((FastSyncException) rootCause).getError());
+      throw new FastSyncException(rootCause);
     } else if (error != null) {
-      LOG.error("Fast sync failed, switching to full sync.", error);
+      LOG.error("Fast sync failed, please try again.", error);
+      throw new FastSyncException(error);
     } else {
       LOG.info(
           "Fast sync completed successfully with pivot block {}",
           result.getPivotBlockNumber().getAsLong());
     }
-    fastSyncDownloader.ifPresent(FastSyncDownloader::deleteFastSyncState);
-
     startFullSync();
   }
 

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

@@ -26,4 +26,9 @@ public class FastSyncException extends RuntimeException {
   public FastSyncError getError() {
     return error;
   }
+
+  public FastSyncException(final Throwable error) {
+    super(error);
+    this.error = FastSyncError.UNEXPECTED_ERROR;
+  }
 }

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

@@ -42,7 +42,7 @@ public class PivotBlockRetriever<C> {
 
   private static final Logger LOG = LogManager.getLogger();
   public static final int MAX_QUERY_RETRIES_PER_PEER = 3;
-  private static final int DEFAULT_MAX_PIVOT_BLOCK_RESETS = 50;
+  private static final int DEFAULT_MAX_PIVOT_BLOCK_RESETS = 250;
   private static final int SUSPICIOUS_NUMBER_OF_RETRIES = 5;
 
   private final EthContext ethContext;