/**
* 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.hdfs;
import java.io.Closeable;
import java.io.FileInputStream;
import java.io.IOException;
import java.lang.ref.WeakReference;
import java.util.Iterator;
import java.util.List;
import java.util.Map.Entry;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hdfs.protocol.DatanodeID;
import org.apache.hadoop.hdfs.protocol.ExtendedBlock;
import org.apache.hadoop.io.IOUtils;
import org.apache.hadoop.util.Time;
import com.google.common.collect.LinkedListMultimap;
import com.google.common.util.concurrent.ThreadFactoryBuilder;
/**
* FileInputStream cache is used to cache FileInputStream objects that we
* have received from the DataNode.
*/
class FileInputStreamCache {
private final static Log LOG = LogFactory.getLog(FileInputStreamCache.class);
/**
* The executor service that runs the cacheCleaner. There is only one of
* these per VM.
*/
private final static ScheduledThreadPoolExecutor executor
= new ScheduledThreadPoolExecutor(1, new ThreadFactoryBuilder().
setDaemon(true).setNameFormat("FileInputStreamCache Cleaner").
build());
/**
* The CacheCleaner for this FileInputStreamCache. We don't create this
* and schedule it until it becomes necessary.
*/
private CacheCleaner cacheCleaner;
/**
* Maximum number of entries to allow in the cache.
*/
private final int maxCacheSize;
/**
* The minimum time in milliseconds to preserve an element in the cache.
*/
private final long expiryTimeMs;
/**
* True if the FileInputStreamCache is closed.
*/
private boolean closed = false;
/**
* Cache entries.
*/
private final LinkedListMultimap<Key, Value> map = LinkedListMultimap.create();
/**
* Expiry thread which makes sure that the file descriptors get closed
* after a while.
*/
private static class CacheCleaner implements Runnable, Closeable {
private WeakReference<FileInputStreamCache> cacheRef;
private ScheduledFuture<?> future;
CacheCleaner(FileInputStreamCache cache) {
this.cacheRef = new WeakReference<FileInputStreamCache>(cache);
}
@Override
public void run() {
FileInputStreamCache cache = cacheRef.get();
if (cache == null) return;
synchronized(cache) {
if (cache.closed) return;
long curTime = Time.monotonicNow();
for (Iterator<Entry<Key, Value>> iter =
cache.map.entries().iterator(); iter.hasNext();
iter = cache.map.entries().iterator()) {
Entry<Key, Value> entry = iter.next();
if (entry.getValue().getTime() + cache.expiryTimeMs >= curTime) {
break;
}
entry.getValue().close();
iter.remove();
}
}
}
@Override
public void close() throws IOException {
if (future != null) {
future.cancel(false);
}
}
public void setFuture(ScheduledFuture<?> future) {
this.future = future;
}
}
/**
* The key identifying a FileInputStream array.
*/
static class Key {
private final DatanodeID datanodeID;
private final ExtendedBlock block;
public Key(DatanodeID datanodeID, ExtendedBlock block) {
this.datanodeID = datanodeID;
this.block = block;
}
@Override
public boolean equals(Object other) {
if (!(other instanceof FileInputStreamCache.Key)) {
return false;
}
FileInputStreamCache.Key otherKey = (FileInputStreamCache.Key)other;
return (block.equals(otherKey.block) &&
(block.getGenerationStamp() == otherKey.block.getGenerationStamp()) &&
datanodeID.equals(otherKey.datanodeID));
}
@Override
public int hashCode() {
return block.hashCode();
}
}
/**
* The value containing a FileInputStream array and the time it was added to
* the cache.
*/
static class Value {
private final FileInputStream fis[];
private final long time;
public Value (FileInputStream fis[]) {
this.fis = fis;
this.time = Time.monotonicNow();
}
public FileInputStream[] getFileInputStreams() {
return fis;
}
public long getTime() {
return time;
}
public void close() {
IOUtils.cleanup(LOG, fis);
}
}
/**
* Create a new FileInputStream
*
* @param maxCacheSize The maximum number of elements to allow in
* the cache.
* @param expiryTimeMs The minimum time in milliseconds to preserve
* elements in the cache.
*/
public FileInputStreamCache(int maxCacheSize, long expiryTimeMs) {
this.maxCacheSize = maxCacheSize;
this.expiryTimeMs = expiryTimeMs;
}
/**
* Put an array of FileInputStream objects into the cache.
*
* @param datanodeID The DatanodeID to store the streams under.
* @param block The Block to store the streams under.
* @param fis The streams.
*/
public void put(DatanodeID datanodeID, ExtendedBlock block,
FileInputStream fis[]) {
boolean inserted = false;
try {
synchronized(this) {
if (closed) return;
if (map.size() + 1 > maxCacheSize) {
Iterator<Entry<Key, Value>> iter = map.entries().iterator();
if (!iter.hasNext()) return;
Entry<Key, Value> entry = iter.next();
entry.getValue().close();
iter.remove();
}
if (cacheCleaner == null) {
cacheCleaner = new CacheCleaner(this);
ScheduledFuture<?> future =
executor.scheduleAtFixedRate(cacheCleaner, expiryTimeMs, expiryTimeMs,
TimeUnit.MILLISECONDS);
cacheCleaner.setFuture(future);
}
map.put(new Key(datanodeID, block), new Value(fis));
inserted = true;
}
} finally {
if (!inserted) {
IOUtils.cleanup(LOG, fis);
}
}
}
/**
* Find and remove an array of FileInputStream objects from the cache.
*
* @param datanodeID The DatanodeID to search for.
* @param block The Block to search for.
*
* @return null if no streams can be found; the
* array otherwise. If this is non-null, the
* array will have been removed from the cache.
*/
public synchronized FileInputStream[] get(DatanodeID datanodeID,
ExtendedBlock block) {
Key key = new Key(datanodeID, block);
List<Value> ret = map.get(key);
if (ret.isEmpty()) return null;
Value val = ret.get(0);
map.remove(key, val);
return val.getFileInputStreams();
}
/**
* Close the cache and free all associated resources.
*/
public synchronized void close() {
if (closed) return;
closed = true;
IOUtils.cleanup(LOG, cacheCleaner);
for (Iterator<Entry<Key, Value>> iter = map.entries().iterator();
iter.hasNext();) {
Entry<Key, Value> entry = iter.next();
entry.getValue().close();
iter.remove();
}
}
public synchronized String toString() {
StringBuilder bld = new StringBuilder();
bld.append("FileInputStreamCache(");
String prefix = "";
for (Entry<Key, Value> entry : map.entries()) {
bld.append(prefix);
bld.append(entry.getKey());
prefix = ", ";
}
bld.append(")");
return bld.toString();
}
public long getExpiryTimeMs() {
return expiryTimeMs;
}
public int getMaxCacheSize() {
return maxCacheSize;
}
}