org.apache.parquet.hadoop.util.HadoopStreams Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
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* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.parquet.hadoop.util;
import java.io.InputStream;
import java.util.Objects;
import java.util.function.Function;
import org.apache.hadoop.fs.ByteBufferReadable;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.parquet.io.PositionOutputStream;
import org.apache.parquet.io.SeekableInputStream;
import org.apache.parquet.util.DynMethods;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Convenience methods to get Parquet abstractions for Hadoop data streams.
*/
public class HadoopStreams {
private static final Logger LOG = LoggerFactory.getLogger(HadoopStreams.class);
private static final DynMethods.UnboundMethod hasCapabilitiesMethod = new DynMethods.Builder("hasCapabilities")
.impl(FSDataInputStream.class, "hasCapabilities", String.class)
.orNoop()
.build();
/**
* Wraps a {@link FSDataInputStream} in a {@link SeekableInputStream}
* implementation for Parquet readers.
*
* @param stream a Hadoop FSDataInputStream
* @return a SeekableInputStream
*/
public static SeekableInputStream wrap(FSDataInputStream stream) {
Objects.requireNonNull(stream, "Cannot wrap a null input stream");
// Try to check using hasCapabilities(str)
Boolean hasCapabilitiesResult = isWrappedStreamByteBufferReadable(stream);
// If it is null, then fall back to the old method
if (hasCapabilitiesResult != null) {
if (hasCapabilitiesResult) {
return new H2SeekableInputStream(stream);
} else {
return new H1SeekableInputStream(stream);
}
}
return unwrapByteBufferReadableLegacy(stream).apply(stream);
}
/**
* Is the inner stream byte buffer readable?
* The test is 'the stream is not FSDataInputStream
* and implements ByteBufferReadable'
*
* This logic is only used for Hadoop <2.9.x, and <3.x.x
*
* @param stream stream to probe
* @return A H2SeekableInputStream to access, or H1SeekableInputStream if the stream is not seekable
*/
private static Function unwrapByteBufferReadableLegacy(
FSDataInputStream stream) {
InputStream wrapped = stream.getWrappedStream();
if (wrapped instanceof FSDataInputStream) {
LOG.debug("Checking on wrapped stream {} of {} whether is ByteBufferReadable", wrapped, stream);
return unwrapByteBufferReadableLegacy(((FSDataInputStream) wrapped));
}
if (stream.getWrappedStream() instanceof ByteBufferReadable) {
return H2SeekableInputStream::new;
} else {
return H1SeekableInputStream::new;
}
}
/**
* 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 successfully support read(ByteBuffer).
* This is true for all filesystem 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, null when it cannot be determined because of missing hasCapabilities
*/
private static Boolean isWrappedStreamByteBufferReadable(FSDataInputStream stream) {
if (hasCapabilitiesMethod.isNoop()) {
// When the method is not available, just return a null
return null;
}
boolean isByteBufferReadable = hasCapabilitiesMethod.invoke(stream, "in:readbytebuffer");
if (isByteBufferReadable) {
// 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;
}
InputStream wrapped = stream.getWrappedStream();
if (wrapped instanceof FSDataInputStream) {
LOG.debug("Checking on wrapped stream {} of {} whether is ByteBufferReadable", wrapped, stream);
return isWrappedStreamByteBufferReadable(((FSDataInputStream) wrapped));
}
return wrapped instanceof ByteBufferReadable;
}
/**
* Wraps a {@link FSDataOutputStream} in a {@link PositionOutputStream}
* implementation for Parquet writers.
*
* @param stream a Hadoop FSDataOutputStream
* @return a SeekableOutputStream
*/
public static PositionOutputStream wrap(FSDataOutputStream stream) {
Objects.requireNonNull(stream, "Cannot wrap a null output stream");
return new HadoopPositionOutputStream(stream);
}
}