HDFS-8885. ByteRangeInputStream used in webhdfs does not override available(). Contributed by Shradha Revankar.

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

@@ -274,4 +274,15 @@ public abstract class ByteRangeInputStream extends FSInputStream {
     }
     status = StreamStatus.CLOSED;
   }
+
+  @Override
+  public synchronized int available() throws IOException{
+    getInputStream();
+    if(fileLength != null){
+      long remaining = fileLength - currentPos;
+      return remaining <= Integer.MAX_VALUE ? (int) remaining : Integer.MAX_VALUE;
+    }else {
+      return Integer.MAX_VALUE;
+    }
+  }
 }

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

@@ -1284,6 +1284,9 @@ Release 2.8.0 - UNRELEASED
 
     HDFS-9003. ForkJoin thread pool leaks. (Kihwal Lee via jing9)
 
+    HDFS-8885. ByteRangeInputStream used in webhdfs does not override
+    available(). (Shradha Revankar via aajisaka)
+
 Release 2.7.2 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/web/TestByteRangeInputStream.java

@@ -210,4 +210,83 @@ public class TestByteRangeInputStream {
 
     verify(mockStream.in, times(isCloses)).close();
   }
+
+
+  @Test
+  public void testAvailable() throws IOException {
+    ByteRangeInputStream bris =
+            mock(ByteRangeInputStream.class, CALLS_REAL_METHODS);
+    InputStreamAndFileLength mockStream = new InputStreamAndFileLength(65535L,
+            mock(InputStream.class));
+    doReturn(mockStream).when(bris).openInputStream(Mockito.anyLong());
+    Whitebox.setInternalState(bris, "status",
+            ByteRangeInputStream.StreamStatus.SEEK);
+
+
+    assertEquals("Before read or seek, available should be same as filelength",
+            65535, bris.available());
+    verify(bris, times(1)).openInputStream(Mockito.anyLong());
+
+    bris.seek(10);
+    assertEquals("Seek 10 bytes, available should return filelength - 10"
+            , 65525,
+            bris.available());
+
+    //no more bytes available
+    bris.seek(65535);
+    assertEquals("Seek till end of file, available should return 0 bytes", 0,
+            bris.available());
+
+    //test reads, seek back to 0 and start reading
+    bris.seek(0);
+    bris.read();
+    assertEquals("Read 1 byte, available must return  filelength - 1",
+            65534, bris.available());
+
+    bris.read();
+    assertEquals("Read another 1 byte, available must return  filelength - 2",
+            65533, bris.available());
+
+    //seek and read
+    bris.seek(100);
+    bris.read();
+    assertEquals("Seek to offset 100 and read 1 byte, available should return filelength - 101",
+            65434, bris.available());
+    bris.close();
+  }
+
+  @Test
+  public void testAvailableLengthNotKnown() throws IOException {
+    ByteRangeInputStream bris =
+            mock(ByteRangeInputStream.class, CALLS_REAL_METHODS);
+    //Length is null for chunked transfer-encoding
+    InputStreamAndFileLength mockStream = new InputStreamAndFileLength(null,
+            mock(InputStream.class));
+    doReturn(mockStream).when(bris).openInputStream(Mockito.anyLong());
+    Whitebox.setInternalState(bris, "status",
+            ByteRangeInputStream.StreamStatus.SEEK);
+
+    assertEquals(Integer.MAX_VALUE, bris.available());
+  }
+
+  @Test
+  public void testAvailableStreamClosed() throws IOException {
+    ByteRangeInputStream bris =
+            mock(ByteRangeInputStream.class, CALLS_REAL_METHODS);
+    InputStreamAndFileLength mockStream = new InputStreamAndFileLength(null,
+            mock(InputStream.class));
+    doReturn(mockStream).when(bris).openInputStream(Mockito.anyLong());
+    Whitebox.setInternalState(bris, "status",
+            ByteRangeInputStream.StreamStatus.SEEK);
+
+    bris.close();
+    try{
+      bris.available();
+      fail("Exception should be thrown when stream is closed");
+    }catch(IOException e){
+      assertTrue("Exception when stream is closed",
+              e.getMessage().equals("Stream closed"));
+    }
+  }
+
 }