Snap client fixes (besu-eth#6847)

* manage empty range for storage
* round rather than floor on max remote connections so that maxpeers=1 still can accept remote connections
---------

Signed-off-by: garyschulte <garyschulte@gmail.com>
Co-authored-by: Karim Taam <karim.t2am@gmail.com>
Co-authored-by: Sally MacFarlane <macfarla.github@gmail.com>

Author: 3 people

CHANGELOG.md

@@ -39,6 +39,7 @@
 - In JSON-RPC return optional `v` fields for type 1 and type 2 transactions [#6762](https://github.com/hyperledger/besu/pull/6762)
 - Fix Shanghai/QBFT block import bug when syncing new nodes [#6765](https://github.com/hyperledger/besu/pull/6765)
 - Fix to avoid broadcasting full blob txs, instead of only the tx announcement, to a subset of nodes [#6835](https://github.com/hyperledger/besu/pull/6835)
+- Snap client fixes discovered during snap server testing [#6847](https://github.com/hyperledger/besu/pull/6847)
 
 ### Download Links
 

besu/src/main/java/org/hyperledger/besu/cli/BesuCommand.java

@@ -1554,7 +1554,7 @@ private void ensureValidPeerBoundParams() {
       checkState(
           fraction >= 0.0 && fraction <= 1.0,
           "Fraction of remote connections allowed must be between 0.0 and 1.0 (inclusive).");
-      maxRemoteInitiatedPeers = (int) Math.floor(fraction * maxPeers);
+      maxRemoteInitiatedPeers = Math.round(fraction * maxPeers);
     } else {
       maxRemoteInitiatedPeers = maxPeers;
     }

ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/sync/snapsync/RequestDataStep.java

@@ -41,6 +41,7 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.NavigableMap;
 import java.util.TreeMap;
 import java.util.concurrent.CompletableFuture;
 import java.util.stream.Collectors;
@@ -49,9 +50,11 @@
 import kotlin.collections.ArrayDeque;
 import org.apache.tuweni.bytes.Bytes;
 import org.apache.tuweni.bytes.Bytes32;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 public class RequestDataStep {
-
+  private static final Logger LOG = LoggerFactory.getLogger(RequestDataStep.class);
   private final WorldStateStorageCoordinator worldStateStorageCoordinator;
   private final SnapSyncProcessState fastSyncState;
   private final SnapWorldDownloadState downloadState;
@@ -131,15 +134,36 @@ public CompletableFuture<List<Task<SnapDataRequest>>> requestStorage(
             (response, error) -> {
               if (response != null) {
                 downloadState.removeOutstandingTask(getStorageRangeTask);
-                for (int i = 0; i < response.slots().size(); i++) {
-                  final StorageRangeDataRequest request =
-                      (StorageRangeDataRequest) requestTasks.get(i).getData();
-                  request.setRootHash(blockHeader.getStateRoot());
-                  request.addResponse(
-                      downloadState,
-                      worldStateProofProvider,
-                      response.slots().get(i),
-                      i < response.slots().size() - 1 ? new ArrayDeque<>() : response.proofs());
+                final ArrayDeque<NavigableMap<Bytes32, Bytes>> slots = new ArrayDeque<>();
+                // Check if we have an empty range
+
+                /*
+                 * Checks if the response represents an "empty range".
+                 *
+                 * An "empty range" is defined as a response where at least one proof exists
+                 * and either no slots are present, or the first slot is empty
+                 */
+                try {
+                  final boolean isEmptyRange =
+                      (response.slots().isEmpty() || response.slots().get(0).isEmpty())
+                          && !response.proofs().isEmpty();
+                  if (isEmptyRange) { // empty range detected
+                    slots.add(new TreeMap<>());
+                  } else {
+                    slots.addAll(response.slots());
+                  }
+                  for (int i = 0; i < slots.size(); i++) {
+                    final StorageRangeDataRequest request =
+                        (StorageRangeDataRequest) requestTasks.get(i).getData();
+                    request.setRootHash(blockHeader.getStateRoot());
+                    request.addResponse(
+                        downloadState,
+                        worldStateProofProvider,
+                        slots.get(i),
+                        i < slots.size() - 1 ? new ArrayDeque<>() : response.proofs());
+                  }
+                } catch (final Exception e) {
+                  LOG.error("Error while processing storage range response", e);
                 }
               }
               return requestTasks;

ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/sync/snapsync/StackTrie.java

@@ -114,6 +114,10 @@ public void commit(final FlatDatabaseUpdater flatDatabaseUpdater, final NodeUpda
                 keys.putAll(taskElement.keys());
               });
 
+      if (keys.isEmpty()) {
+        return; // empty range we can ignore it
+      }
+
       final Map<Bytes32, Bytes> proofsEntries = new HashMap<>();
       for (Bytes proof : proofs) {
         proofsEntries.put(Hash.hash(proof), proof);