HADOOP-12974. Create a CachingGetSpaceUsed implementation that uses df. Contributed by Elliott Clark.

(cherry picked from commit 57aec2b46b)
(cherry picked from commit a6863e5334)

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/DFCachingGetSpaceUsed.java

@@ -0,0 +1,48 @@
+/**
+ * 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.fs;
+
+import org.apache.hadoop.classification.InterfaceAudience;
+import org.apache.hadoop.classification.InterfaceStability;
+
+import java.io.IOException;
+
+/**
+ * Fast but inaccurate class to tell how much space HDFS is using.
+ * This class makes the assumption that the entire mount is used for
+ * HDFS and that no two hdfs data dirs are on the same disk.
+ *
+ * To use set fs.getspaceused.classname
+ * to org.apache.hadoop.fs.DFCachingGetSpaceUsed in your core-site.xml
+ *
+ */
+@InterfaceAudience.LimitedPrivate({"HDFS", "MapReduce"})
+@InterfaceStability.Evolving
+public class DFCachingGetSpaceUsed extends CachingGetSpaceUsed {
+  private final DF df;
+
+  public DFCachingGetSpaceUsed(Builder builder) throws IOException {
+    super(builder);
+    this.df = new DF(builder.getPath(), builder.getInterval());
+  }
+
+  @Override
+  protected void refresh() {
+    this.used.set(df.getUsed());
+  }
+}

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/DU.java

@@ -31,12 +31,13 @@ import java.io.IOException;
 @InterfaceAudience.LimitedPrivate({"HDFS", "MapReduce"})
 @InterfaceStability.Evolving
 public class DU extends CachingGetSpaceUsed {
-  private DUShell duShell;
+  private final DUShell duShell;
 
   @VisibleForTesting
    public DU(File path, long interval, long jitter, long initialUsed)
       throws IOException {
     super(path, interval, jitter, initialUsed);
+    this.duShell = new DUShell();
   }
 
   public DU(CachingGetSpaceUsed.Builder builder) throws IOException {
@@ -48,9 +49,6 @@ public class DU extends CachingGetSpaceUsed {
 
   @Override
   protected synchronized void refresh() {
-    if (duShell == null) {
-      duShell = new DUShell();
-    }
     try {
       duShell.startRefresh();
     } catch (IOException ioe) {

hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/fs/TestDFCachingGetSpaceUsed.java

@@ -0,0 +1,76 @@
+/**
+ * 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
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * 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.fs;
+
+import org.apache.commons.lang.RandomStringUtils;
+import org.apache.hadoop.test.GenericTestUtils;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.RandomAccessFile;
+
+
+import static org.junit.Assert.assertTrue;
+
+/**
+ * Test to make sure df can run and work.
+ */
+public class TestDFCachingGetSpaceUsed {
+  final static private File DF_DIR =
+      new File(System.getProperty("test.build.data","/tmp"), "testdfspace");
+  public static final int FILE_SIZE = 1024;
+
+  @Before
+  public void setUp() {
+    FileUtil.fullyDelete(DF_DIR);
+    assertTrue(DF_DIR.mkdirs());
+  }
+
+  @After
+  public void tearDown() throws IOException {
+    FileUtil.fullyDelete(DF_DIR);
+  }
+
+  @Test
+  public void testCanBuildRun() throws Exception {
+    File file = writeFile("testCanBuild");
+
+    GetSpaceUsed instance = new CachingGetSpaceUsed.Builder()
+        .setPath(file)
+        .setInterval(50060)
+        .setKlass(DFCachingGetSpaceUsed.class)
+        .build();
+    assertTrue(instance instanceof DFCachingGetSpaceUsed);
+    assertTrue(instance.getUsed() >= FILE_SIZE - 20);
+    ((DFCachingGetSpaceUsed) instance).close();
+  }
+
+  private File writeFile(String fileName) throws IOException {
+    File f = new File(DF_DIR, fileName);
+    assertTrue(f.createNewFile());
+    RandomAccessFile randomAccessFile = new RandomAccessFile(f, "rws");
+    randomAccessFile.writeUTF(RandomStringUtils.randomAlphabetic(FILE_SIZE));
+    randomAccessFile.getFD().sync();
+    randomAccessFile.close();
+    return f;
+  }
+
+}