HDFS-14215. RBF: Remove dependency on availability of default namespace. Contributed by Ayush Saxena.

hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterClientProtocol.java

@@ -201,8 +201,7 @@ public FsServerDefaults getServerDefaults() throws IOException {
     rpcServer.checkOperation(NameNode.OperationCategory.READ);
 
     RemoteMethod method = new RemoteMethod("getServerDefaults");
-    String ns = subclusterResolver.getDefaultNamespace();
-    return (FsServerDefaults) rpcClient.invokeSingle(ns, method);
+    return rpcServer.invokeAtAvailableNs(method, FsServerDefaults.class);
   }
 
   @Override

hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterNamenodeProtocol.java

@@ -24,7 +24,6 @@
 import org.apache.hadoop.hdfs.protocol.DatanodeInfo;
 import org.apache.hadoop.hdfs.protocol.HdfsConstants.DatanodeReportType;
 import org.apache.hadoop.hdfs.security.token.block.ExportedBlockKeys;
-import org.apache.hadoop.hdfs.server.federation.resolver.FileSubclusterResolver;
 import org.apache.hadoop.hdfs.server.namenode.CheckpointSignature;
 import org.apache.hadoop.hdfs.server.namenode.NameNode.OperationCategory;
 import org.apache.hadoop.hdfs.server.protocol.BlocksWithLocations;
@@ -45,14 +44,11 @@ public class RouterNamenodeProtocol implements NamenodeProtocol {
   private final RouterRpcServer rpcServer;
   /** RPC clients to connect to the Namenodes. */
   private final RouterRpcClient rpcClient;
-  /** Interface to map global name space to HDFS subcluster name spaces. */
-  private final FileSubclusterResolver subclusterResolver;
 
 
   public RouterNamenodeProtocol(RouterRpcServer server) {
     this.rpcServer = server;
     this.rpcClient =  this.rpcServer.getRPCClient();
-    this.subclusterResolver = this.rpcServer.getSubclusterResolver();
   }
 
   @Override
@@ -94,33 +90,27 @@ public BlocksWithLocations getBlocks(DatanodeInfo datanode, long size,
   public ExportedBlockKeys getBlockKeys() throws IOException {
     rpcServer.checkOperation(OperationCategory.READ);
 
-    // We return the information from the default name space
-    String defaultNsId = subclusterResolver.getDefaultNamespace();
     RemoteMethod method =
         new RemoteMethod(NamenodeProtocol.class, "getBlockKeys");
-    return rpcClient.invokeSingle(defaultNsId, method, ExportedBlockKeys.class);
+    return rpcServer.invokeAtAvailableNs(method, ExportedBlockKeys.class);
   }
 
   @Override
   public long getTransactionID() throws IOException {
     rpcServer.checkOperation(OperationCategory.READ);
 
-    // We return the information from the default name space
-    String defaultNsId = subclusterResolver.getDefaultNamespace();
     RemoteMethod method =
         new RemoteMethod(NamenodeProtocol.class, "getTransactionID");
-    return rpcClient.invokeSingle(defaultNsId, method, long.class);
+    return rpcServer.invokeAtAvailableNs(method, long.class);
   }
 
   @Override
   public long getMostRecentCheckpointTxId() throws IOException {
     rpcServer.checkOperation(OperationCategory.READ);
 
-    // We return the information from the default name space
-    String defaultNsId = subclusterResolver.getDefaultNamespace();
     RemoteMethod method =
         new RemoteMethod(NamenodeProtocol.class, "getMostRecentCheckpointTxId");
-    return rpcClient.invokeSingle(defaultNsId, method, long.class);
+    return rpcServer.invokeAtAvailableNs(method, long.class);
   }
 
   @Override
@@ -133,11 +123,9 @@ public CheckpointSignature rollEditLog() throws IOException {
   public NamespaceInfo versionRequest() throws IOException {
     rpcServer.checkOperation(OperationCategory.READ);
 
-    // We return the information from the default name space
-    String defaultNsId = subclusterResolver.getDefaultNamespace();
     RemoteMethod method =
         new RemoteMethod(NamenodeProtocol.class, "versionRequest");
-    return rpcClient.invokeSingle(defaultNsId, method, NamespaceInfo.class);
+    return rpcServer.invokeAtAvailableNs(method, NamespaceInfo.class);
   }
 
   @Override

hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterRpcServer.java

@@ -479,6 +479,29 @@ static String getMethodName() {
     return methodName;
   }
 
+  /**
+   * Invokes the method at default namespace, if default namespace is not
+   * available then at the first available namespace.
+   * @param <T> expected return type.
+   * @param method the remote method.
+   * @return the response received after invoking method.
+   * @throws IOException
+   */
+  <T> T invokeAtAvailableNs(RemoteMethod method, Class<T> clazz)
+      throws IOException {
+    String nsId = subclusterResolver.getDefaultNamespace();
+    if (!nsId.isEmpty()) {
+      return rpcClient.invokeSingle(nsId, method, clazz);
+    }
+    // If default Ns is not present return result from first namespace.
+    Set<FederationNamespaceInfo> nss = namenodeResolver.getNamespaces();
+    if (nss.isEmpty()) {
+      throw new IOException("No namespace availaible.");
+    }
+    nsId = nss.iterator().next().getNameserviceId();
+    return rpcClient.invokeSingle(nsId, method, clazz);
+  }
+
   @Override // ClientProtocol
   public Token<DelegationTokenIdentifier> getDelegationToken(Text renewer)
       throws IOException {

hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/router/RouterStoragePolicy.java

@@ -18,7 +18,6 @@
 package org.apache.hadoop.hdfs.server.federation.router;
 
 import org.apache.hadoop.hdfs.protocol.BlockStoragePolicy;
-import org.apache.hadoop.hdfs.server.federation.resolver.FileSubclusterResolver;
 import org.apache.hadoop.hdfs.server.federation.resolver.RemoteLocation;
 import org.apache.hadoop.hdfs.server.namenode.NameNode;
 
@@ -36,13 +35,10 @@ public class RouterStoragePolicy {
   private final RouterRpcServer rpcServer;
   /** RPC clients to connect to the Namenodes. */
   private final RouterRpcClient rpcClient;
-  /** Interface to map global name space to HDFS subcluster name spaces. */
-  private final FileSubclusterResolver subclusterResolver;
 
   public RouterStoragePolicy(RouterRpcServer server) {
     this.rpcServer = server;
     this.rpcClient = this.rpcServer.getRPCClient();
-    this.subclusterResolver = this.rpcServer.getSubclusterResolver();
   }
 
   public void setStoragePolicy(String src, String policyName)
@@ -61,8 +57,7 @@ public BlockStoragePolicy[] getStoragePolicies() throws IOException {
     rpcServer.checkOperation(NameNode.OperationCategory.READ);
 
     RemoteMethod method = new RemoteMethod("getStoragePolicies");
-    String ns = subclusterResolver.getDefaultNamespace();
-    return (BlockStoragePolicy[]) rpcClient.invokeSingle(ns, method);
+    return rpcServer.invokeAtAvailableNs(method, BlockStoragePolicy[].class);
   }
 
   public void unsetStoragePolicy(String src) throws IOException {

hadoop-hdfs-project/hadoop-hdfs-rbf/src/test/java/org/apache/hadoop/hdfs/server/federation/MockResolver.java

@@ -57,6 +57,7 @@ public class MockResolver
   private Map<String, List<RemoteLocation>> locations = new HashMap<>();
   private Set<FederationNamespaceInfo> namespaces = new HashSet<>();
   private String defaultNamespace = null;
+  private boolean disableDefaultNamespace = false;
 
   public MockResolver() {
     this.cleanRegistrations();
@@ -322,8 +323,19 @@ public List<String> getMountPoints(String path) throws IOException {
   public void setRouterId(String router) {
   }
 
+  /**
+   * Mocks the availability of default namespace.
+   * @param b if true default namespace is unset.
+   */
+  public void setDisableNamespace(boolean b) {
+    this.disableDefaultNamespace = b;
+  }
+
   @Override
   public String getDefaultNamespace() {
+    if (disableDefaultNamespace) {
+      return "";
+    }
     return defaultNamespace;
   }
 }

hadoop-hdfs-project/hadoop-hdfs-rbf/src/test/java/org/apache/hadoop/hdfs/server/federation/router/TestRouterRpc.java

@@ -56,6 +56,7 @@
 import org.apache.hadoop.fs.FileContext;
 import org.apache.hadoop.fs.FileStatus;
 import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.FsServerDefaults;
 import org.apache.hadoop.fs.Options;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.fs.permission.FsPermission;
@@ -828,6 +829,40 @@ public void testProxyGetAndUnsetStoragePolicy() throws Exception {
     assertEquals(nnPolicy.getId(), policy.getId());
   }
 
+  @Test
+  public void testListStoragePolicies() throws IOException, URISyntaxException {
+    MockResolver resolver =
+        (MockResolver) router.getRouter().getSubclusterResolver();
+    try {
+      // Check with default namespace specified.
+      BlockStoragePolicy[] policies = namenode.getClient().getStoragePolicies();
+      assertArrayEquals(policies, routerProtocol.getStoragePolicies());
+      // Check with default namespace unspecified.
+      resolver.setDisableNamespace(true);
+      assertArrayEquals(policies, routerProtocol.getStoragePolicies());
+    } finally {
+      resolver.setDisableNamespace(false);
+    }
+  }
+
+  @Test
+  public void testGetServerDefaults() throws IOException, URISyntaxException {
+    MockResolver resolver =
+        (MockResolver) router.getRouter().getSubclusterResolver();
+    try {
+      // Check with default namespace specified.
+      FsServerDefaults defaults = namenode.getClient().getServerDefaults();
+      assertEquals(defaults.getBlockSize(),
+          routerProtocol.getServerDefaults().getBlockSize());
+      // Check with default namespace unspecified.
+      resolver.setDisableNamespace(true);
+      assertEquals(defaults.getBlockSize(),
+          routerProtocol.getServerDefaults().getBlockSize());
+    } finally {
+      resolver.setDisableNamespace(false);
+    }
+  }
+
   @Test
   public void testProxyGetPreferedBlockSize() throws Exception {
 
@@ -1012,8 +1047,23 @@ public void testProxyGetFileInfoAcessException() throws IOException {
 
   @Test
   public void testProxyVersionRequest() throws Exception {
-    NamespaceInfo rVersion = routerNamenodeProtocol.versionRequest();
-    NamespaceInfo nnVersion = nnNamenodeProtocol.versionRequest();
+    MockResolver resolver =
+        (MockResolver) router.getRouter().getSubclusterResolver();
+    try {
+      // Check with default namespace specified.
+      NamespaceInfo rVersion = routerNamenodeProtocol.versionRequest();
+      NamespaceInfo nnVersion = nnNamenodeProtocol.versionRequest();
+      compareVersion(rVersion, nnVersion);
+      // Check with default namespace unspecified.
+      resolver.setDisableNamespace(true);
+      rVersion = routerNamenodeProtocol.versionRequest();
+      compareVersion(rVersion, nnVersion);
+    } finally {
+      resolver.setDisableNamespace(false);
+    }
+  }
+
+  private void compareVersion(NamespaceInfo rVersion, NamespaceInfo nnVersion) {
     assertEquals(nnVersion.getBlockPoolID(), rVersion.getBlockPoolID());
     assertEquals(nnVersion.getNamespaceID(), rVersion.getNamespaceID());
     assertEquals(nnVersion.getClusterID(), rVersion.getClusterID());
@@ -1023,8 +1073,24 @@ public void testProxyVersionRequest() throws Exception {
 
   @Test
   public void testProxyGetBlockKeys() throws Exception {
-    ExportedBlockKeys rKeys = routerNamenodeProtocol.getBlockKeys();
-    ExportedBlockKeys nnKeys = nnNamenodeProtocol.getBlockKeys();
+    MockResolver resolver =
+        (MockResolver) router.getRouter().getSubclusterResolver();
+    try {
+      // Check with default namespace specified.
+      ExportedBlockKeys rKeys = routerNamenodeProtocol.getBlockKeys();
+      ExportedBlockKeys nnKeys = nnNamenodeProtocol.getBlockKeys();
+      compareBlockKeys(rKeys, nnKeys);
+      // Check with default namespace unspecified.
+      resolver.setDisableNamespace(true);
+      rKeys = routerNamenodeProtocol.getBlockKeys();
+      compareBlockKeys(rKeys, nnKeys);
+    } finally {
+      resolver.setDisableNamespace(false);
+    }
+  }
+
+  private void compareBlockKeys(ExportedBlockKeys rKeys,
+      ExportedBlockKeys nnKeys) {
     assertEquals(nnKeys.getCurrentKey(), rKeys.getCurrentKey());
     assertEquals(nnKeys.getKeyUpdateInterval(), rKeys.getKeyUpdateInterval());
     assertEquals(nnKeys.getTokenLifetime(), rKeys.getTokenLifetime());
@@ -1054,17 +1120,38 @@ public void testProxyGetBlocks() throws Exception {
 
   @Test
   public void testProxyGetTransactionID() throws IOException {
-    long routerTransactionID = routerNamenodeProtocol.getTransactionID();
-    long nnTransactionID = nnNamenodeProtocol.getTransactionID();
-    assertEquals(nnTransactionID, routerTransactionID);
+    MockResolver resolver =
+        (MockResolver) router.getRouter().getSubclusterResolver();
+    try {
+      // Check with default namespace specified.
+      long routerTransactionID = routerNamenodeProtocol.getTransactionID();
+      long nnTransactionID = nnNamenodeProtocol.getTransactionID();
+      assertEquals(nnTransactionID, routerTransactionID);
+      // Check with default namespace unspecified.
+      resolver.setDisableNamespace(true);
+      routerTransactionID = routerNamenodeProtocol.getTransactionID();
+      assertEquals(nnTransactionID, routerTransactionID);
+    } finally {
+      resolver.setDisableNamespace(false);
+    }
   }
 
   @Test
   public void testProxyGetMostRecentCheckpointTxId() throws IOException {
-    long routerCheckPointId =
-        routerNamenodeProtocol.getMostRecentCheckpointTxId();
-    long nnCheckPointId = nnNamenodeProtocol.getMostRecentCheckpointTxId();
-    assertEquals(nnCheckPointId, routerCheckPointId);
+    MockResolver resolver =
+        (MockResolver) router.getRouter().getSubclusterResolver();
+    try {
+      // Check with default namespace specified.
+      long routerCheckPointId =
+          routerNamenodeProtocol.getMostRecentCheckpointTxId();
+      long nnCheckPointId = nnNamenodeProtocol.getMostRecentCheckpointTxId();
+      assertEquals(nnCheckPointId, routerCheckPointId);
+      // Check with default namespace unspecified.
+      resolver.setDisableNamespace(true);
+      routerCheckPointId = routerNamenodeProtocol.getMostRecentCheckpointTxId();
+    } finally {
+      resolver.setDisableNamespace(false);
+    }
   }
 
   @Test