HDFS-10662. Optimize UTF8 string/byte conversions. Contributed by Daryn Sharp.

(cherry picked from commit 6ae39199da)

Conflicts:
	hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSDirWriteFileOp.java

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

@@ -82,11 +82,21 @@ public class DFSUtilClient {
   public static final byte[] EMPTY_BYTES = {};
   private static final Logger LOG = LoggerFactory.getLogger(
       DFSUtilClient.class);
+
+  // Using the charset canonical name for String/byte[] conversions is much
+  // more efficient due to use of cached encoders/decoders.
+  private static final String UTF8_CSN = StandardCharsets.UTF_8.name();
+
   /**
    * Converts a string to a byte array using UTF8 encoding.
    */
   public static byte[] string2Bytes(String str) {
-    return str.getBytes(StandardCharsets.UTF_8);
+    try {
+      return str.getBytes(UTF8_CSN);
+    } catch (UnsupportedEncodingException e) {
+      // should never happen!
+      throw new IllegalArgumentException("UTF8 decoding is not supported", e);
+    }
   }
 
   /**
@@ -272,13 +282,13 @@ public class DFSUtilClient {
    * @param length The number of bytes to decode
    * @return The decoded string
    */
-  private static String bytes2String(byte[] bytes, int offset, int length) {
+  static String bytes2String(byte[] bytes, int offset, int length) {
     try {
-      return new String(bytes, offset, length, "UTF8");
-    } catch(UnsupportedEncodingException e) {
-      assert false : "UTF8 encoding is not supported ";
+      return new String(bytes, offset, length, UTF8_CSN);
+    } catch (UnsupportedEncodingException e) {
+      // should never happen!
+      throw new IllegalArgumentException("UTF8 encoding is not supported", e);
     }
-    return null;
   }
 
   /**

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

@@ -38,7 +38,6 @@ import static org.apache.hadoop.hdfs.DFSConfigKeys.DFS_SERVER_HTTPS_TRUSTSTORE_P
 
 import java.io.IOException;
 import java.io.PrintStream;
-import java.io.UnsupportedEncodingException;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.net.URI;
@@ -249,12 +248,7 @@ public class DFSUtil {
    * @return The decoded string
    */
   public static String bytes2String(byte[] bytes, int offset, int length) {
-    try {
-      return new String(bytes, offset, length, "UTF8");
-    } catch(UnsupportedEncodingException e) {
-      assert false : "UTF8 encoding is not supported ";
-    }
-    return null;
+    return DFSUtilClient.bytes2String(bytes, 0, bytes.length);
   }
 
   /**

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

@@ -32,7 +32,6 @@ import org.apache.hadoop.hdfs.protocol.QuotaExceededException;
 import org.apache.hadoop.hdfs.server.namenode.snapshot.Snapshot;
 
 import java.io.IOException;
-import java.nio.charset.StandardCharsets;
 import java.util.AbstractMap;
 import java.util.List;
 import java.util.Map;
@@ -121,8 +120,7 @@ class FSDirMkdirOp {
   static Map.Entry<INodesInPath, String> createAncestorDirectories(
       FSDirectory fsd, INodesInPath iip, PermissionStatus permission)
       throws IOException {
-    final String last =
-        new String(iip.getLastLocalName(), StandardCharsets.UTF_8);
+    final String last = DFSUtil.bytes2String(iip.getLastLocalName());
     INodesInPath existing = iip.getExistingINodes();
     List<String> children = iip.getPath(existing.length(),
         iip.length() - existing.length());
@@ -190,7 +188,7 @@ class FSDirMkdirOp {
       throws IOException {
     assert fsd.hasWriteLock();
     existing = unprotectedMkdir(fsd, fsd.allocateNewInodeId(), existing,
-        localName.getBytes(StandardCharsets.UTF_8), perm, null, now());
+        DFSUtil.string2Bytes(localName), perm, null, now());
     if (existing == null) {
       return null;
     }

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

@@ -43,7 +43,6 @@ import org.apache.hadoop.hdfs.util.ReadOnlyList;
 
 import java.io.FileNotFoundException;
 import java.io.IOException;
-import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
 
 import static org.apache.hadoop.util.Time.now;
@@ -53,8 +52,7 @@ class FSDirStatAndListingOp {
       byte[] startAfter, boolean needLocation) throws IOException {
     byte[][] pathComponents = FSDirectory
         .getPathComponentsForReservedPath(srcArg);
-    final String startAfterString =
-        new String(startAfter, StandardCharsets.UTF_8);
+    final String startAfterString = DFSUtil.bytes2String(startAfter);
     String src = null;
 
     if (fsd.isPermissionEnabled()) {

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

@@ -32,6 +32,7 @@ import org.apache.hadoop.fs.permission.AclEntry;
 import org.apache.hadoop.fs.permission.FsAction;
 import org.apache.hadoop.fs.permission.PermissionStatus;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
+import org.apache.hadoop.hdfs.DFSUtil;
 import org.apache.hadoop.hdfs.protocol.Block;
 import org.apache.hadoop.hdfs.protocol.BlockStoragePolicy;
 import org.apache.hadoop.hdfs.protocol.ClientProtocol;
@@ -56,7 +57,6 @@ import org.apache.hadoop.util.ChunkedArrayList;
 
 import java.io.FileNotFoundException;
 import java.io.IOException;
-import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -564,7 +564,7 @@ class FSDirWriteFileOp {
     long modTime = now();
     INodeFile newNode = newINodeFile(fsd.allocateNewInodeId(), permissions,
                                      modTime, modTime, replication, preferredBlockSize);
-    newNode.setLocalName(localName.getBytes(StandardCharsets.UTF_8));
+    newNode.setLocalName(DFSUtil.string2Bytes(localName));
     newNode.toUnderConstruction(clientName, clientMachine);
 
     INodesInPath newiip;

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

@@ -18,7 +18,6 @@
 package org.apache.hadoop.hdfs.server.namenode;
 
 import com.google.common.annotations.VisibleForTesting;
-import com.google.common.base.Charsets;
 import com.google.common.base.Preconditions;
 import com.google.common.collect.Lists;
 import org.apache.hadoop.HadoopIllegalArgumentException;
@@ -26,6 +25,7 @@ import org.apache.hadoop.fs.XAttr;
 import org.apache.hadoop.fs.XAttrSetFlag;
 import org.apache.hadoop.fs.permission.FsAction;
 import org.apache.hadoop.hdfs.DFSConfigKeys;
+import org.apache.hadoop.hdfs.DFSUtil;
 import org.apache.hadoop.hdfs.XAttrHelper;
 import org.apache.hadoop.hdfs.protocol.HdfsFileStatus;
 import org.apache.hadoop.hdfs.protocol.proto.HdfsProtos;
@@ -410,7 +410,7 @@ class FSDirXAttrOp {
    * the configured limit. Setting a limit of zero disables this check.
    */
   private static void checkXAttrSize(FSDirectory fsd, XAttr xAttr) {
-    int size = xAttr.getName().getBytes(Charsets.UTF_8).length;
+    int size = DFSUtil.string2Bytes(xAttr.getName()).length;
     if (xAttr.getValue() != null) {
       size += xAttr.getValue().length;
     }