[GitHub] [parquet-mr] sunchao commented on a diff in pull request #971: PARQUET-2134: Improve binding to ByteBufferReadable

2022-07-14 Thread GitBox


sunchao commented on code in PR #971:
URL: https://github.com/apache/parquet-mr/pull/971#discussion_r921361565


##
parquet-hadoop/src/main/java/org/apache/parquet/hadoop/util/HadoopStreams.java:
##
@@ -50,51 +46,45 @@ public class HadoopStreams {
*/
   public static SeekableInputStream wrap(FSDataInputStream stream) {
 Objects.requireNonNull(stream, "Cannot wrap a null input stream");
-if (byteBufferReadableClass != null && h2SeekableConstructor != null &&
-byteBufferReadableClass.isInstance(stream.getWrappedStream())) {
-  try {
-return h2SeekableConstructor.newInstance(stream);
-  } catch (InstantiationException | IllegalAccessException e) {
-LOG.warn("Could not instantiate H2SeekableInputStream, falling back to 
byte array reads", e);
-return new H1SeekableInputStream(stream);
-  } catch (InvocationTargetException e) {
-throw new ParquetDecodingException(
-"Could not instantiate H2SeekableInputStream", 
e.getTargetException());
-  }
+if (isWrappedStreamByteBufferReadable(stream)) {
+  return new H2SeekableInputStream(stream);
 } else {
   return new H1SeekableInputStream(stream);
 }
   }
 
-  private static Class getReadableClass() {
-try {
-  return Class.forName("org.apache.hadoop.fs.ByteBufferReadable");
-} catch (ClassNotFoundException | NoClassDefFoundError e) {
-  return null;
+  /**
+   * Is the inner stream byte buffer readable?
+   * The test is "the stream is not FSDataInputStream
+   * and implements ByteBufferReadable'
+   *
+   * That is: all streams which implement ByteBufferReadable
+   * other than FSDataInputStream successfuly support read(ByteBuffer).
+   * This is true for all filesytem clients the hadoop codebase.
+   *
+   * In hadoop 3.3.0+, the StreamCapabilities probe can be used to
+   * check this: only those streams which provide the read(ByteBuffer)
+   * semantics MAY return true for the probe "in:readbytebuffer";
+   * FSDataInputStream will pass the probe down to the underlying stream.
+   *
+   * @param stream stream to probe
+   * @return true if it is safe to a H2SeekableInputStream to access the data
+   */
+  private static boolean isWrappedStreamByteBufferReadable(FSDataInputStream 
stream) {
+if (stream.hasCapability("in:readbytebuffer")) {

Review Comment:
   Personally I'm in favor of moving on and adopt the new APIs especially if we 
are going to depend on Hadoop 3 features more. Maybe we can call the next 
Parquet release 1.13.0 and declare that it's no longer compatible with older 
Hadoop versions? 
   
   cc @shangxinli 



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[GitHub] [parquet-mr] sunchao commented on a diff in pull request #971: PARQUET-2134: Improve binding to ByteBufferReadable

2022-07-13 Thread GitBox


sunchao commented on code in PR #971:
URL: https://github.com/apache/parquet-mr/pull/971#discussion_r920576934


##
parquet-hadoop/src/main/java/org/apache/parquet/hadoop/util/HadoopStreams.java:
##
@@ -50,51 +46,45 @@ public class HadoopStreams {
*/
   public static SeekableInputStream wrap(FSDataInputStream stream) {
 Objects.requireNonNull(stream, "Cannot wrap a null input stream");
-if (byteBufferReadableClass != null && h2SeekableConstructor != null &&
-byteBufferReadableClass.isInstance(stream.getWrappedStream())) {
-  try {
-return h2SeekableConstructor.newInstance(stream);
-  } catch (InstantiationException | IllegalAccessException e) {
-LOG.warn("Could not instantiate H2SeekableInputStream, falling back to 
byte array reads", e);
-return new H1SeekableInputStream(stream);
-  } catch (InvocationTargetException e) {
-throw new ParquetDecodingException(
-"Could not instantiate H2SeekableInputStream", 
e.getTargetException());
-  }
+if (isWrappedStreamByteBufferReadable(stream)) {
+  return new H2SeekableInputStream(stream);
 } else {
   return new H1SeekableInputStream(stream);
 }
   }
 
-  private static Class getReadableClass() {
-try {
-  return Class.forName("org.apache.hadoop.fs.ByteBufferReadable");
-} catch (ClassNotFoundException | NoClassDefFoundError e) {
-  return null;
+  /**
+   * Is the inner stream byte buffer readable?
+   * The test is "the stream is not FSDataInputStream
+   * and implements ByteBufferReadable'
+   *
+   * That is: all streams which implement ByteBufferReadable
+   * other than FSDataInputStream successfuly support read(ByteBuffer).
+   * This is true for all filesytem clients the hadoop codebase.
+   *
+   * In hadoop 3.3.0+, the StreamCapabilities probe can be used to
+   * check this: only those streams which provide the read(ByteBuffer)
+   * semantics MAY return true for the probe "in:readbytebuffer";
+   * FSDataInputStream will pass the probe down to the underlying stream.
+   *
+   * @param stream stream to probe
+   * @return true if it is safe to a H2SeekableInputStream to access the data
+   */
+  private static boolean isWrappedStreamByteBufferReadable(FSDataInputStream 
stream) {
+if (stream.hasCapability("in:readbytebuffer")) {
+  // stream is issuing the guarantee that it implements the
+  // API. Holds for all implementations in hadoop-*
+  // since Hadoop 3.3.0 (HDFS-14111).
+  return true;
 }
-  }
-
-  @SuppressWarnings("unchecked")

Review Comment:
   I don't understand why Parquet need to use reflection to look up a class 
defined by itself.



##
parquet-hadoop/src/main/java/org/apache/parquet/hadoop/util/HadoopStreams.java:
##
@@ -50,51 +46,45 @@ public class HadoopStreams {
*/
   public static SeekableInputStream wrap(FSDataInputStream stream) {
 Objects.requireNonNull(stream, "Cannot wrap a null input stream");
-if (byteBufferReadableClass != null && h2SeekableConstructor != null &&
-byteBufferReadableClass.isInstance(stream.getWrappedStream())) {
-  try {
-return h2SeekableConstructor.newInstance(stream);
-  } catch (InstantiationException | IllegalAccessException e) {
-LOG.warn("Could not instantiate H2SeekableInputStream, falling back to 
byte array reads", e);
-return new H1SeekableInputStream(stream);
-  } catch (InvocationTargetException e) {
-throw new ParquetDecodingException(
-"Could not instantiate H2SeekableInputStream", 
e.getTargetException());
-  }
+if (isWrappedStreamByteBufferReadable(stream)) {
+  return new H2SeekableInputStream(stream);
 } else {
   return new H1SeekableInputStream(stream);
 }
   }
 
-  private static Class getReadableClass() {
-try {
-  return Class.forName("org.apache.hadoop.fs.ByteBufferReadable");
-} catch (ClassNotFoundException | NoClassDefFoundError e) {
-  return null;
+  /**
+   * Is the inner stream byte buffer readable?
+   * The test is "the stream is not FSDataInputStream
+   * and implements ByteBufferReadable'
+   *
+   * That is: all streams which implement ByteBufferReadable
+   * other than FSDataInputStream successfuly support read(ByteBuffer).
+   * This is true for all filesytem clients the hadoop codebase.
+   *
+   * In hadoop 3.3.0+, the StreamCapabilities probe can be used to
+   * check this: only those streams which provide the read(ByteBuffer)
+   * semantics MAY return true for the probe "in:readbytebuffer";
+   * FSDataInputStream will pass the probe down to the underlying stream.
+   *
+   * @param stream stream to probe
+   * @return true if it is safe to a H2SeekableInputStream to access the data
+   */
+  private static boolean isWrappedStreamByteBufferReadable(FSDataInputStream 
stream) {
+if (stream.hasCapability("in:readbytebuffer")) {

Review Comment:
   it appears this is a