[GitHub] [hadoop] goiri commented on a diff in pull request #5123: HDFS-16837. [RBF SBN] ClientGSIContext should merge RouterFederatedStates to get the max state id for each namespaces

[GitBox <gi...@apache.org>]

goiri commented on code in PR #5123:
URL: https://github.com/apache/hadoop/pull/5123#discussion_r1019478547


##########
hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/ClientGSIContext.java:
##########
@@ -77,12 +82,35 @@ public void updateResponseState(RpcResponseHeaderProto.Builder header) {
   @Override
   public synchronized void receiveResponseState(RpcResponseHeaderProto header) {
     if (header.hasRouterFederatedState()) {
-      routerFederatedState = header.getRouterFederatedState();
+      routerFederatedState = mergeRouterFederatedState(header.getRouterFederatedState());
+      routerFederatedState = mergeRouterFederatedState(header.getRouterFederatedState());
     } else {
       lastSeenStateId.accumulate(header.getStateId());
     }
   }
 
+  /**
+   * Merge the local FederatedState and RemoteFederateState to get the max value for each namespace.
+   * @param remoteFederateState the remote RouterFederatedState.
+   * @return one ByteString object which contains the max value of each namespace.
+   */
+  private ByteString mergeRouterFederatedState(ByteString remoteFederateState) {
+    Map<String, Long> localMapping = new HashMap<>(
+        ByteStringUtil.getRouterFederatedStateMap(this.routerFederatedState));
+    Map<String, Long> remoteMapping =
+        ByteStringUtil.getRouterFederatedStateMap(remoteFederateState);
+
+    for (String ns : remoteMapping.keySet()) {
+      long remoteValue = remoteMapping.get(ns);
+      long localValue = localMapping.getOrDefault(ns, 0L);
+      localMapping.put(ns, Math.max(remoteValue, localValue));
+    }
+    HdfsServerFederationProtos.RouterFederatedStateProto.Builder federatedStateBuilder =

Review Comment:
   To make it shorter to read, can you import org.apache.hadoop.hdfs.federation.protocol.proto.HdfsServerFederationProtos.RouterFederatedStateProto?



##########
hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/util/ByteStringUtil.java:
##########
@@ -0,0 +1,46 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+package org.apache.hadoop.hdfs.util;
+
+import org.apache.hadoop.hdfs.federation.protocol.proto.HdfsServerFederationProtos;
+import org.apache.hadoop.thirdparty.protobuf.ByteString;
+import org.apache.hadoop.thirdparty.protobuf.InvalidProtocolBufferException;
+
+import java.util.Collections;
+import java.util.Map;
+
+public class ByteStringUtil {
+
+  /**
+   * Utility function to parse routerFederatedState field in RPC headers.
+   */
+  public static Map<String, Long> getRouterFederatedStateMap(
+      ByteString byteString) {
+    if (byteString != null) {

Review Comment:
   To make it easier to read:
   ```
   if (byteString == null) {
      return Collections.emptyMap();
   }
   ```



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