[GitHub] [hadoop] simbadzina commented on a diff in pull request #4311: HDFS-13522: IPC changes to support observer reads through routers.

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

simbadzina commented on code in PR #4311:
URL: https://github.com/apache/hadoop/pull/4311#discussion_r964131419


##########
hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/FederatedNamespaceIds.java:
##########
@@ -0,0 +1,113 @@
+/**
+ * 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.server.federation.router;
+
+import java.util.Collections;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.locks.ReentrantLock;
+import org.apache.hadoop.classification.VisibleForTesting;
+import org.apache.hadoop.hdfs.NamespaceStateId;
+import org.apache.hadoop.ipc.protobuf.RpcHeaderProtos;
+import org.apache.hadoop.hdfs.federation.protocol.proto.HdfsServerFederationProtos.RouterFederatedStateProto;
+import org.apache.hadoop.thirdparty.protobuf.InvalidProtocolBufferException;
+import org.apache.hadoop.thirdparty.protobuf.ByteString;
+
+
+/**
+ * Collection of last-seen namespace state Ids for a set of namespaces.
+ * A single NamespaceStateId is shared by all outgoing connections to a particular namespace.
+ * Router clients share and query the entire collection.
+ */
+public class FederatedNamespaceIds {
+  private final Map<String, NamespaceStateId> namespaceIdMap = new ConcurrentHashMap<>();
+  private final ReentrantLock lock = new ReentrantLock();
+
+  public void updateStateUsingRequestHeader(RpcHeaderProtos.RpcRequestHeaderProto header) {
+    if (header.hasRouterFederatedState()) {
+      RouterFederatedStateProto federatedState;
+      try {
+        federatedState = RouterFederatedStateProto.parseFrom(header.getRouterFederatedState());
+      } catch (InvalidProtocolBufferException e) {
+        throw new RuntimeException(e);
+      }
+      lock.lock();
+      try {
+        federatedState.getNamespaceStateIdsMap().forEach((nsId, stateId) -> {
+          if (!namespaceIdMap.containsKey(nsId)) {
+            namespaceIdMap.putIfAbsent(nsId, new NamespaceStateId());
+          }
+          namespaceIdMap.get(nsId).update(stateId);
+        });
+      } finally {
+        lock.unlock();
+      }
+
+    }
+  }
+
+  public void setResponseHeaderState(RpcHeaderProtos.RpcResponseHeaderProto.Builder headerBuilder) {
+    RouterFederatedStateProto.Builder federatedStateBuilder =
+        RouterFederatedStateProto.newBuilder();
+    lock.lock();
+    try {
+      namespaceIdMap.forEach((k, v) -> federatedStateBuilder.putNamespaceStateIds(k, v.get()));
+    } finally {
+      lock.unlock();
+    }
+    headerBuilder.setRouterFederatedState(federatedStateBuilder.build().toByteString());
+  }
+
+  public NamespaceStateId getNamespaceId(String nsId) {
+    lock.lock();
+    try {
+      namespaceIdMap.putIfAbsent(nsId, new NamespaceStateId());
+    } finally {
+      lock.unlock();
+    }
+    return namespaceIdMap.get(nsId);
+  }
+
+  public void removeNamespaceId(String nsId) {
+    lock.lock();
+    try {
+      namespaceIdMap.remove(nsId);
+    } finally {
+      lock.unlock();
+    }
+  }
+
+  /**
+   * Utility function to view state of routerFederatedState field in RPC headers.
+   */
+  @VisibleForTesting
+  public static Map<String, Long> getRouterFederatedStateMap(ByteString byteString) {

Review Comment:
   I now use this class in the RouterRPCClient.



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