HADOOP-15677. WASB: Add support for StreamCapabilities.

Contributed by Thomas Marquardt.

hadoop-tools/hadoop-azure/src/main/java/org/apache/hadoop/fs/azure/PageBlobOutputStream.java

@@ -29,11 +29,13 @@ import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
 import java.util.Arrays;
+import java.util.Locale;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.ThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
 
+import org.apache.hadoop.fs.StreamCapabilities;
 import org.apache.hadoop.fs.Syncable;
 import org.apache.hadoop.fs.azure.StorageInterface.CloudPageBlobWrapper;
 import org.apache.commons.lang3.exception.ExceptionUtils;
@@ -52,7 +54,7 @@ import com.microsoft.azure.storage.blob.CloudPageBlob;
  * An output stream that write file data to a page blob stored using ASV's
  * custom format.
  */
-final class PageBlobOutputStream extends OutputStream implements Syncable {
+final class PageBlobOutputStream extends OutputStream implements Syncable, StreamCapabilities {
   /**
    * The maximum number of raw bytes Azure Storage allows us to upload in a
    * single request (4 MB).
@@ -195,6 +197,23 @@ final class PageBlobOutputStream extends OutputStream implements Syncable {
     }
   }
 
+  /**
+   * Query the stream for a specific capability.
+   *
+   * @param capability string to query the stream support for.
+   * @return true for hsync and hflush.
+   */
+  @Override
+  public boolean hasCapability(String capability) {
+    switch (capability.toLowerCase(Locale.ENGLISH)) {
+      case StreamCapabilities.HSYNC:
+      case StreamCapabilities.HFLUSH:
+        return true;
+      default:
+        return false;
+    }
+  }
+
   /**
    * Closes this output stream and releases any system resources associated with
    * this stream. If any data remains in the buffer it is committed to the

hadoop-tools/hadoop-azure/src/test/java/org/apache/hadoop/fs/azure/ITestOutputStreamSemantics.java

@@ -34,6 +34,7 @@ import org.apache.hadoop.fs.FSDataInputStream;
 import org.apache.hadoop.fs.FSDataOutputStream;
 import org.apache.hadoop.fs.Path;
 
+import org.apache.hadoop.fs.StreamCapabilities;
 import org.hamcrest.core.IsEqual;
 import org.hamcrest.core.IsNot;
 import org.junit.Test;
@@ -186,6 +187,20 @@ public class ITestOutputStreamSemantics extends AbstractWasbTestBase {
     }
   }
 
+  // Page Blobs have StreamCapabilities.HFLUSH and StreamCapabilities.HSYNC.
+  @Test
+  public void testPageBlobCapabilities() throws IOException {
+    Path path = getBlobPathWithTestName(PAGE_BLOB_DIR);
+    try (FSDataOutputStream stream = fs.create(path)) {
+      assertTrue(stream.hasCapability(StreamCapabilities.HFLUSH));
+      assertTrue(stream.hasCapability(StreamCapabilities.HSYNC));
+      assertFalse(stream.hasCapability(StreamCapabilities.DROPBEHIND));
+      assertFalse(stream.hasCapability(StreamCapabilities.READAHEAD));
+      assertFalse(stream.hasCapability(StreamCapabilities.UNBUFFER));
+      stream.write(getRandomBytes());
+    }
+  }
+
   // Verify flush does not write data to storage for Block Blobs
   @Test
   public void testBlockBlobFlush() throws Exception {
@@ -265,6 +280,20 @@ public class ITestOutputStreamSemantics extends AbstractWasbTestBase {
     }
   }
 
+  // Block Blobs do not have any StreamCapabilities.
+  @Test
+  public void testBlockBlobCapabilities() throws IOException {
+    Path path = getBlobPathWithTestName(BLOCK_BLOB_DIR);
+    try (FSDataOutputStream stream = fs.create(path)) {
+      assertFalse(stream.hasCapability(StreamCapabilities.HFLUSH));
+      assertFalse(stream.hasCapability(StreamCapabilities.HSYNC));
+      assertFalse(stream.hasCapability(StreamCapabilities.DROPBEHIND));
+      assertFalse(stream.hasCapability(StreamCapabilities.READAHEAD));
+      assertFalse(stream.hasCapability(StreamCapabilities.UNBUFFER));
+      stream.write(getRandomBytes());
+    }
+  }
+
   // Verify flush writes data to storage for Block Blobs with compaction
   @Test
   public void testBlockBlobCompactionFlush() throws Exception {
@@ -347,6 +376,20 @@ public class ITestOutputStreamSemantics extends AbstractWasbTestBase {
     }
   }
 
+  // Block Blobs with Compaction have StreamCapabilities.HFLUSH and HSYNC.
+  @Test
+  public void testBlockBlobCompactionCapabilities() throws IOException {
+    Path path = getBlobPathWithTestName(BLOCK_BLOB_COMPACTION_DIR);
+    try (FSDataOutputStream stream = fs.create(path)) {
+      assertTrue(stream.hasCapability(StreamCapabilities.HFLUSH));
+      assertTrue(stream.hasCapability(StreamCapabilities.HSYNC));
+      assertFalse(stream.hasCapability(StreamCapabilities.DROPBEHIND));
+      assertFalse(stream.hasCapability(StreamCapabilities.READAHEAD));
+      assertFalse(stream.hasCapability(StreamCapabilities.UNBUFFER));
+      stream.write(getRandomBytes());
+    }
+  }
+
   // A small write does not write data to storage for Page Blobs
   @Test
   public void testPageBlobSmallWrite() throws IOException {