AVRO-2511: add case for sync (apache#2392)

* AVRO-2511: add case for sync

lang/java/avro/src/main/java/org/apache/avro/file/DataFileWriter.java

@@ -22,6 +22,7 @@
 import java.io.BufferedOutputStream;
 import java.io.Closeable;
 import java.io.File;
+import java.io.FileOutputStream;
 import java.io.FilterOutputStream;
 import java.io.Flushable;
 import java.io.IOException;
@@ -51,7 +52,7 @@
  * <i>blocks</i>. A synchronization marker is written between blocks, so that
  * files may be split. Blocks may be compressed. Extensible metadata is stored
  * at the end of the file. Files may be appended to.
- * 
+ *
  * @see DataFileReader
  */
 public class DataFileWriter<D> implements Closeable, Flushable {
@@ -181,7 +182,7 @@ public DataFileWriter<D> create(Schema schema, OutputStream outs, byte[] sync) t
    * sync marker is written. By default, the writer will flush the buffer each
    * time a sync marker is written (if the block size limit is reached or the
    * {@linkplain #sync()} is called.
-   * 
+   *
    * @param flushOnEveryBlock - If set to false, this writer will not flush the
    *                          block to the stream until {@linkplain #flush()} is
    *                          explicitly called.
@@ -211,7 +212,7 @@ public DataFileWriter<D> appendTo(File file) throws IOException {
   /**
    * Open a writer appending to an existing file. <strong>Since 1.9.0 this method
    * does not close in.</strong>
-   * 
+   *
    * @param in  reading the existing file.
    * @param out positioned at the end of the existing file.
    */
@@ -304,7 +305,7 @@ public AppendWriteException(Exception e) {
 
   /**
    * Append a datum to the file.
-   * 
+   *
    * @see AppendWriteException
    */
   public void append(D datum) throws IOException {
@@ -365,7 +366,7 @@ private void writeIfBlockFull() throws IOException {
    * at compression level 7. If <i>recompress</i> is false, blocks will be copied
    * without changing the compression level. If true, they will be converted to
    * the new compression level.
-   * 
+   *
    * @param otherFile
    * @param recompress
    * @throws IOException
@@ -439,17 +440,19 @@ public void flush() throws IOException {
   }
 
   /**
-   * If this writer was instantiated using a File or using an
-   * {@linkplain Syncable} instance, this method flushes all buffers for this
-   * writer to disk. In other cases, this method behaves exactly like
-   * {@linkplain #flush()}.
+   * If this writer was instantiated using a {@linkplain File},
+   * {@linkplain FileOutputStream} or {@linkplain Syncable} instance, this method
+   * flushes all buffers for this writer to disk. In other cases, this method
+   * behaves exactly like {@linkplain #flush()}.
    *
    * @throws IOException
    */
   public void fSync() throws IOException {
     flush();
     if (underlyingStream instanceof Syncable) {
       ((Syncable) underlyingStream).sync();
+    } else if (underlyingStream instanceof FileOutputStream) {
+      ((FileOutputStream) underlyingStream).getFD().sync();
     }
   }