HDFS-8640. Make reserved RBW space visible through JMX. (Contributed by kanaka kumar avvaru)

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

@@ -669,6 +669,9 @@ Release 2.8.0 - UNRELEASED
     HDFS-8462. Implement GETXATTRS and LISTXATTRS operations for WebImageViewer.
     (Jagadesh Kiran N via aajisaka)
 
+    HDFS-8640. Make reserved RBW space visible through JMX. (kanaka kumar
+    avvaru via Arpit Agarwal)
+
   OPTIMIZATIONS
 
     HDFS-8026. Trace FSOutputSummer#writeChecksumChunks rather than

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/FsDatasetImpl.java

@@ -2559,13 +2559,15 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
     final String directory;
     final long usedSpace; // size of space used by HDFS
     final long freeSpace; // size of free space excluding reserved space
-    final long reservedSpace; // size of space reserved for non-HDFS and RBW
+    final long reservedSpace; // size of space reserved for non-HDFS
+    final long reservedSpaceForRBW; // size of space reserved RBW
 
     VolumeInfo(FsVolumeImpl v, long usedSpace, long freeSpace) {
       this.directory = v.toString();
       this.usedSpace = usedSpace;
       this.freeSpace = freeSpace;
       this.reservedSpace = v.getReserved();
+      this.reservedSpaceForRBW = v.getReservedForRbw();
     }
   }  
 
@@ -2599,6 +2601,7 @@ class FsDatasetImpl implements FsDatasetSpi<FsVolumeImpl> {
       innerInfo.put("usedSpace", v.usedSpace);
       innerInfo.put("freeSpace", v.freeSpace);
       innerInfo.put("reservedSpace", v.reservedSpace);
+      innerInfo.put("reservedSpaceForRBW", v.reservedSpaceForRBW);
       info.put(v.directory, innerInfo);
     }
     return info;

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/TestRbwSpaceReservation.java

@@ -49,11 +49,15 @@ import org.mockito.Mockito;
 
 import java.io.IOException;
 import java.io.OutputStream;
+import java.lang.management.ManagementFactory;
 import java.lang.reflect.Field;
 import java.util.Map;
 import java.util.Random;
 import java.util.concurrent.TimeoutException;
 
+import javax.management.MBeanServer;
+import javax.management.ObjectName;
+
 /**
  * Ensure that the DN reserves disk space equivalent to a full block for
  * replica being written (RBW).
@@ -324,6 +328,30 @@ public class TestRbwSpaceReservation {
         fsVolumeImpl.getReservedForRbw() == 0);
   }
 
+  @Test(timeout = 30000)
+  public void testRBWInJMXBean() throws Exception {
+
+    final short replication = 1;
+    startCluster(BLOCK_SIZE, replication, -1);
+
+    final String methodName = GenericTestUtils.getMethodName();
+    final Path file = new Path("/" + methodName + ".01.dat");
+
+    try (FSDataOutputStream os = fs.create(file, replication)) {
+      // Write 1 byte to the file
+      os.write(new byte[1]);
+      os.hsync();
+
+      final MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
+      final ObjectName mxbeanName = new ObjectName(
+          "Hadoop:service=DataNode,name=DataNodeInfo");
+      final String volumeInfo = (String) mbs.getAttribute(mxbeanName,
+          "VolumeInfo");
+
+      assertTrue(volumeInfo.contains("reservedSpaceForRBW"));
+    }
+  }
+
   /**
    * Stress test to ensure we are not leaking reserved space.
    * @throws IOException