org.apache.hadoop.fs.statistics.BufferedIOStatisticsOutputStream Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* 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.hadoop.fs.statistics;
import java.io.BufferedOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import org.apache.hadoop.fs.StreamCapabilities;
import org.apache.hadoop.fs.Syncable;
import static org.apache.hadoop.fs.statistics.IOStatisticsSupport.retrieveIOStatistics;
/**
* An extension of {@code BufferedOutputStream} which implements
* {@link IOStatisticsSource} and forwards requests for the
* {@link IOStatistics} to the wrapped stream.
*
* This should be used when any output stream needs buffering while
* allowing the inner stream to be a source of statistics.
*
* It also implements {@link StreamCapabilities}
* and {@link Syncable} and forwards to to the inner stream,
* if possible.
*/
public class BufferedIOStatisticsOutputStream
extends BufferedOutputStream
implements IOStatisticsSource, Syncable, StreamCapabilities {
/**
* Should calls to Syncable downgrade to flush if the underlying
* stream does not support it?
* While that breaks a core contract requirement of Syncable:
* "Sync.sync() guarantees durability", downgrading is
* the default behavior of FsDataOutputStream.
*/
private final boolean downgradeSyncable;
/**
* Construct with default buffer size.
* @param out output stream to buffer
* @param downgradeSyncable should Syncable calls downgrade?
*/
public BufferedIOStatisticsOutputStream(
final OutputStream out,
final boolean downgradeSyncable) {
super(out);
this.downgradeSyncable = downgradeSyncable;
}
/**
* Construct with custom buffer size.
*
* @param out output stream to buffer
* @param size buffer.
* @param downgradeSyncable should Syncable calls downgrade?
*/
public BufferedIOStatisticsOutputStream(
final OutputStream out,
final int size,
final boolean downgradeSyncable) {
super(out, size);
this.downgradeSyncable = downgradeSyncable;
}
/**
* Ask the inner stream for their IOStatistics.
* @return any IOStatistics offered by the inner stream.
*/
@Override
public IOStatistics getIOStatistics() {
return retrieveIOStatistics(out);
}
/**
* If the inner stream supports {@link StreamCapabilities},
* forward the probe to it.
* Otherwise: return false.
*
* @param capability string to query the stream support for.
* @return true if a capability is known to be supported.
*/
@Override
public boolean hasCapability(final String capability) {
if (out instanceof StreamCapabilities) {
return ((StreamCapabilities) out).hasCapability(capability);
} else {
return false;
}
}
/**
* If the inner stream is Syncable, flush the buffer and then
* invoke the inner stream's hflush() operation.
*
* Otherwise: throw an exception, unless the stream was constructed with
* {@link #downgradeSyncable} set to true, in which case the stream
* is just flushed.
* @throws IOException IO Problem
* @throws UnsupportedOperationException if the inner class is not syncable
*/
@Override
public void hflush() throws IOException {
if (out instanceof Syncable) {
flush();
((Syncable) out).hflush();
} else {
if (!downgradeSyncable) {
throw new UnsupportedOperationException("hflush not supported by "
+ out);
} else {
flush();
}
}
}
/**
* If the inner stream is Syncable, flush the buffer and then
* invoke the inner stream's hsync() operation.
*
* Otherwise: throw an exception, unless the stream was constructed with
* {@link #downgradeSyncable} set to true, in which case the stream
* is just flushed.
* @throws IOException IO Problem
* @throws UnsupportedOperationException if the inner class is not syncable
*/
@Override
public void hsync() throws IOException {
if (out instanceof Syncable) {
flush();
((Syncable) out).hsync();
} else {
if (!downgradeSyncable) {
throw new UnsupportedOperationException("hsync not supported by "
+ out);
} else {
flush();
}
}
}
}