HDFS-16764. [SBN Read] ObserverNamenode should throw ObserverRetryOnActiveException instead of FileNotFoundException during processing of addBlock rpc (#4872)

Signed-off-by: Erik Krogen <xkrogen@apache.org>
Co-authored-by: zengqiang.xu <zengqiang.xu@shopee.com>

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSNamesystem.java

@@ -3044,12 +3044,12 @@ public class FSNamesystem implements Namesystem, FSNamesystemMBean,
 
     LocatedBlock[] onRetryBlock = new LocatedBlock[1];
     FSDirWriteFileOp.ValidateAddBlockResult r;
-    checkOperation(OperationCategory.READ);
+    checkOperation(OperationCategory.WRITE);
     final FSPermissionChecker pc = getPermissionChecker();
     FSPermissionChecker.setOperationType(operationName);
     readLock();
     try {
-      checkOperation(OperationCategory.READ);
+      checkOperation(OperationCategory.WRITE);
       r = FSDirWriteFileOp.validateAddBlock(this, pc, src, fileId, clientName,
                                             previous, onRetryBlock);
     } finally {
@@ -3095,12 +3095,15 @@ public class FSNamesystem implements Namesystem, FSNamesystemMBean,
     final byte storagePolicyID;
     final List<DatanodeStorageInfo> chosen;
     final BlockType blockType;
-    checkOperation(OperationCategory.READ);
+    checkOperation(OperationCategory.WRITE);
     final FSPermissionChecker pc = getPermissionChecker();
     FSPermissionChecker.setOperationType(null);
     readLock();
     try {
-      checkOperation(OperationCategory.READ);
+      // Changing this operation category to WRITE instead of making getAdditionalDatanode as a
+      // read method is aim to let Active NameNode to handle this RPC, because Active NameNode
+      // contains a more complete DN selection context than Observer NameNode.
+      checkOperation(OperationCategory.WRITE);
       //check safe mode
       checkNameNodeSafeMode("Cannot add datanode; src=" + src + ", blk=" + blk);
       final INodesInPath iip = dir.resolvePath(pc, src, fileId);

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/namenode/TestNameNodeRpcServer.java

@@ -29,26 +29,32 @@ import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_NAMENODE_RPC_BIND_HOST_KE
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotEquals;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
 
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import java.security.PrivilegedExceptionAction;
+import java.util.EnumSet;
 
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.FSDataOutputStream;
 import org.apache.hadoop.fs.FileSystem;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.fs.permission.FsPermission;
+import org.apache.hadoop.hdfs.AddBlockFlag;
 import org.apache.hadoop.hdfs.DFSTestUtil;
 import org.apache.hadoop.hdfs.DistributedFileSystem;
 import org.apache.hadoop.hdfs.HdfsConfiguration;
 import org.apache.hadoop.hdfs.MiniDFSCluster;
 
+import org.apache.hadoop.hdfs.protocol.HdfsFileStatus;
 import org.apache.hadoop.hdfs.protocol.LocatedBlocks;
 import org.apache.hadoop.hdfs.qjournal.MiniQJMHACluster;
 import org.apache.hadoop.ipc.CallerContext;
+import org.apache.hadoop.ipc.ObserverRetryOnActiveException;
 import org.apache.hadoop.security.UserGroupInformation;
 import org.apache.hadoop.test.GenericTestUtils;
+import org.apache.hadoop.test.LambdaTestUtils;
 import org.junit.Test;
 import org.junit.jupiter.api.Timeout;
 
@@ -158,6 +164,43 @@ public class TestNameNodeRpcServer {
     }
   }
 
+  @Test
+  @Timeout(30000)
+  public void testObserverHandleAddBlock() throws Exception {
+    String baseDir = GenericTestUtils.getRandomizedTempPath();
+    Configuration conf = new HdfsConfiguration();
+    MiniQJMHACluster.Builder builder = new MiniQJMHACluster.Builder(conf).setNumNameNodes(3);
+    builder.getDfsBuilder().numDataNodes(3);
+    try (MiniQJMHACluster qjmhaCluster = builder.baseDir(baseDir).build()) {
+      MiniDFSCluster dfsCluster = qjmhaCluster.getDfsCluster();
+      dfsCluster.waitActive();
+      dfsCluster.transitionToActive(0);
+      dfsCluster.transitionToObserver(2);
+
+      NameNode activeNN = dfsCluster.getNameNode(0);
+      NameNode observerNN = dfsCluster.getNameNode(2);
+
+      // Stop the editLogTailer of Observer NameNode
+      observerNN.getNamesystem().getEditLogTailer().stop();
+      DistributedFileSystem dfs = dfsCluster.getFileSystem(0);
+
+      Path testPath = new Path("/testObserverHandleAddBlock/file.txt");
+      try (FSDataOutputStream ignore = dfs.create(testPath)) {
+        HdfsFileStatus fileStatus = activeNN.getRpcServer().getFileInfo(testPath.toUri().getPath());
+        assertNotNull(fileStatus);
+        assertNull(observerNN.getRpcServer().getFileInfo(testPath.toUri().getPath()));
+
+        LambdaTestUtils.intercept(ObserverRetryOnActiveException.class, () -> {
+          observerNN.getRpcServer().addBlock(testPath.toUri().getPath(),
+              dfs.getClient().getClientName(), null, null,
+              fileStatus.getFileId(), null, EnumSet.noneOf(AddBlockFlag.class));
+        });
+      } finally {
+        dfs.delete(testPath, true);
+      }
+    }
+  }
+
   /**
    * A test to make sure that if an authorized user adds "clientIp:" to their
    * caller context, it will be used to make locality decisions on the NN.