HDFS-8815. DFS getStoragePolicy implementation using single RPC call (Contributed by Surendra Singh Lilhore)

(cherry picked from commit cc71ad80e184fc6e5043729e8cfcf6a62ca3e71f)

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/protocol/ClientProtocol.java

@@ -279,6 +279,20 @@ public interface ClientProtocol {
   void setStoragePolicy(String src, String policyName)
       throws IOException;
 
+  /**
+   * Get the storage policy for a file/directory.
+   * @param path
+   *          Path of an existing file/directory.
+   * @throws AccessControlException
+   *           If access is denied
+   * @throws org.apache.hadoop.fs.UnresolvedLinkException
+   *           if <code>src</code> contains a symlink
+   * @throws java.io.FileNotFoundException
+   *           If file/dir <code>src</code> is not found
+   */
+  @Idempotent
+  BlockStoragePolicy getStoragePolicy(String path) throws IOException;
+
   /**
    * Set permissions for an existing file/directory.
    *

hadoop-hdfs-project/hadoop-hdfs-client/src/main/proto/ClientNamenodeProtocol.proto

@@ -112,6 +112,14 @@ message SetStoragePolicyRequestProto {
 message SetStoragePolicyResponseProto { // void response
 }
 
+message GetStoragePolicyRequestProto {
+  required string path = 1;
+}
+
+message GetStoragePolicyResponseProto {
+  required BlockStoragePolicyProto storagePolicy = 1;
+}
+
 message GetStoragePoliciesRequestProto { // void request
 }
 
@@ -722,6 +730,8 @@ service ClientNamenodeProtocol {
       returns(SetReplicationResponseProto);
   rpc setStoragePolicy(SetStoragePolicyRequestProto)
       returns(SetStoragePolicyResponseProto);
+  rpc getStoragePolicy(GetStoragePolicyRequestProto)
+      returns(GetStoragePolicyResponseProto);
   rpc getStoragePolicies(GetStoragePoliciesRequestProto)
       returns(GetStoragePoliciesResponseProto);
   rpc setPermission(SetPermissionRequestProto)

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -427,6 +427,9 @@ Release 2.8.0 - UNRELEASED
 
     HDFS-6860. BlockStateChange logs are too noisy. (Chang Li and xyao via xyao)
 
+    HDFS-8815. DFS getStoragePolicy implementation using single RPC call
+    (Surendra Singh Lilhore via vinayakumarb)
+
   OPTIMIZATIONS
 
     HDFS-8026. Trace FSOutputSummer#writeChecksumChunks rather than

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSClient.java

@@ -1568,21 +1568,22 @@ public class DFSClient implements java.io.Closeable, RemotePeerFactory,
   }
 
   /**
+   * @param path file/directory name
    * @return Get the storage policy for specified path
    */
   public BlockStoragePolicy getStoragePolicy(String path) throws IOException {
-    HdfsFileStatus status = getFileInfo(path);
-    if (status == null) {
-      throw new FileNotFoundException("File does not exist: " + path);
-    }
-    byte storagePolicyId = status.getStoragePolicy();
-    BlockStoragePolicy[] policies = getStoragePolicies();
-    for (BlockStoragePolicy policy : policies) {
-      if (policy.getId() == storagePolicyId) {
-        return policy;
-      }
+    checkOpen();
+    TraceScope scope = getPathTraceScope("getStoragePolicy", path);
+    try {
+      return namenode.getStoragePolicy(path);
+    } catch (RemoteException e) {
+      throw e.unwrapRemoteException(AccessControlException.class,
+                                    FileNotFoundException.class,
+                                    SafeModeException.class,
+                                    UnresolvedPathException.class);
+    } finally {
+      scope.close();
     }
-    return null;
   }
 
   /**

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientNamenodeProtocolServerSideTranslatorPB.java

@@ -128,6 +128,8 @@ import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetSna
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetSnapshottableDirListingResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetStoragePoliciesRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetStoragePoliciesResponseProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetStoragePolicyRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetStoragePolicyResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.IsFileClosedRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.IsFileClosedResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ListCacheDirectivesRequestProto;
@@ -198,6 +200,7 @@ import org.apache.hadoop.hdfs.protocol.proto.EncryptionZonesProtos.GetEZForPathR
 import org.apache.hadoop.hdfs.protocol.proto.EncryptionZonesProtos.GetEZForPathRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.EncryptionZonesProtos.ListEncryptionZonesResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.EncryptionZonesProtos.ListEncryptionZonesRequestProto;
+import org.apache.hadoop.hdfs.protocol.proto.HdfsProtos.BlockStoragePolicyProto;
 import org.apache.hadoop.hdfs.protocol.proto.HdfsProtos.DatanodeIDProto;
 import org.apache.hadoop.hdfs.protocol.proto.HdfsProtos.DatanodeInfoProto;
 import org.apache.hadoop.hdfs.protocol.proto.HdfsProtos.LocatedBlockProto;
@@ -1459,6 +1462,20 @@ public class ClientNamenodeProtocolServerSideTranslatorPB implements
     return VOID_SET_STORAGE_POLICY_RESPONSE;
   }
 
+  @Override
+  public GetStoragePolicyResponseProto getStoragePolicy(
+      RpcController controller, GetStoragePolicyRequestProto request)
+      throws ServiceException {
+    try {
+      BlockStoragePolicyProto policy = PBHelper.convert(server
+          .getStoragePolicy(request.getPath()));
+      return GetStoragePolicyResponseProto.newBuilder()
+          .setStoragePolicy(policy).build();
+    } catch (IOException e) {
+      throw new ServiceException(e);
+    }
+  }
+
   @Override
   public GetStoragePoliciesResponseProto getStoragePolicies(
       RpcController controller, GetStoragePoliciesRequestProto request)

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/ClientNamenodeProtocolTranslatorPB.java

@@ -124,6 +124,7 @@ import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetSna
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetSnapshottableDirListingResponseProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetStoragePoliciesRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetStoragePoliciesResponseProto;
+import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.GetStoragePolicyRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.IsFileClosedRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ListCacheDirectivesRequestProto;
 import org.apache.hadoop.hdfs.protocol.proto.ClientNamenodeProtocolProtos.ListCacheDirectivesResponseProto;
@@ -1482,6 +1483,18 @@ public class ClientNamenodeProtocolTranslatorPB implements
     }
   }
 
+  @Override
+  public BlockStoragePolicy getStoragePolicy(String path) throws IOException {
+    GetStoragePolicyRequestProto request = GetStoragePolicyRequestProto
+        .newBuilder().setPath(path).build();
+    try {
+      return PBHelper.convert(rpcProxy.getStoragePolicy(null, request)
+          .getStoragePolicy());
+    } catch (ServiceException e) {
+      throw ProtobufHelper.getRemoteException(e);
+    }
+  }
+
   @Override
   public BlockStoragePolicy[] getStoragePolicies() throws IOException {
     try {

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

@@ -200,6 +200,29 @@ public class FSDirAttrOp {
     return bm.getStoragePolicies();
   }
 
+  static BlockStoragePolicy getStoragePolicy(FSDirectory fsd, BlockManager bm,
+      String path) throws IOException {
+    FSPermissionChecker pc = fsd.getPermissionChecker();
+    byte[][] pathComponents = FSDirectory
+        .getPathComponentsForReservedPath(path);
+    fsd.readLock();
+    try {
+      path = fsd.resolvePath(pc, path, pathComponents);
+      final INodesInPath iip = fsd.getINodesInPath(path, false);
+      if (fsd.isPermissionEnabled()) {
+        fsd.checkPathAccess(pc, iip, FsAction.READ);
+      }
+      INode inode = iip.getLastINode();
+      if (inode == null) {
+        throw new FileNotFoundException("File/Directory does not exist: "
+            + iip.getPath());
+      }
+      return bm.getStoragePolicy(inode.getStoragePolicyID());
+    } finally {
+      fsd.readUnlock();
+    }
+  }
+
   static long getPreferredBlockSize(FSDirectory fsd, String src)
       throws IOException {
     FSPermissionChecker pc = fsd.getPermissionChecker();

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

@@ -1948,6 +1948,25 @@ public class FSNamesystem implements Namesystem, FSNamesystemMBean,
     logAuditEvent(true, "setStoragePolicy", src, null, auditStat);
   }
 
+  /**
+   * Get the storage policy for a file or a directory.
+   *
+   * @param src
+   *          file/directory path
+   * @return storage policy object
+   */
+  BlockStoragePolicy getStoragePolicy(String src) throws IOException {
+    checkOperation(OperationCategory.READ);
+    waitForLoadingFSImage();
+    readLock();
+    try {
+      checkOperation(OperationCategory.READ);
+      return FSDirAttrOp.getStoragePolicy(dir, blockManager, src);
+    } finally {
+      readUnlock();
+    }
+  }
+
   /**
    * @return All the existing block storage policies
    */

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

@@ -685,6 +685,12 @@ class NameNodeRpcServer implements NamenodeProtocols {
     namesystem.setStoragePolicy(src, policyName);
   }
 
+  @Override
+  public BlockStoragePolicy getStoragePolicy(String path) throws IOException {
+    checkNNStartup();
+    return namesystem.getStoragePolicy(path);
+  }
+
   @Override
   public BlockStoragePolicy[] getStoragePolicies() throws IOException {
     checkNNStartup();

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/TestBlockStoragePolicy.java

@@ -979,6 +979,29 @@ public class TestBlockStoragePolicy {
     }
   }
 
+  @Test
+  public void testGetStoragePolicy() throws Exception {
+    final MiniDFSCluster cluster = new MiniDFSCluster.Builder(conf)
+        .numDataNodes(REPLICATION).build();
+    cluster.waitActive();
+    final DistributedFileSystem fs = cluster.getFileSystem();
+    try {
+      final Path dir = new Path("/testGetStoragePolicy");
+      final Path fooFile = new Path(dir, "foo");
+      DFSTestUtil.createFile(fs, fooFile, FILE_LEN, REPLICATION, 0L);
+      DFSClient client = new DFSClient(cluster.getNameNode(0)
+          .getNameNodeAddress(), conf);
+      client.setStoragePolicy("/testGetStoragePolicy/foo",
+          HdfsConstants.COLD_STORAGE_POLICY_NAME);
+      String policyName = client.getStoragePolicy("/testGetStoragePolicy/foo")
+          .getName();
+      Assert.assertEquals("File storage policy should be COLD",
+          HdfsConstants.COLD_STORAGE_POLICY_NAME, policyName);
+    } finally {
+      cluster.shutdown();
+    }
+  }
+
   @Test
   public void testSetStoragePolicyWithSnapshot() throws Exception {
     final MiniDFSCluster cluster = new MiniDFSCluster.Builder(conf)