/**
* 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.util.Iterator;
import java.util.List;
import java.util.Map.Entry;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Preconditions;
import com.google.common.collect.LinkedListMultimap;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hdfs.protocol.DatanodeID;
import org.apache.hadoop.io.IOUtils;
import org.apache.hadoop.hdfs.net.Peer;
import org.apache.hadoop.util.Daemon;
import org.apache.hadoop.util.Time;
/**
* A cache of input stream sockets to Data Node.
*/
class PeerCache {
private static final Log LOG = LogFactory.getLog(PeerCache.class);
private static class Key {
final DatanodeID dnID;
final boolean isDomain;
Key(DatanodeID dnID, boolean isDomain) {
this.dnID = dnID;
this.isDomain = isDomain;
}
@Override
public boolean equals(Object o) {
if (!(o instanceof Key)) {
return false;
}
Key other = (Key)o;
return dnID.equals(other.dnID) && isDomain == other.isDomain;
}
@Override
public int hashCode() {
return dnID.hashCode() ^ (isDomain ? 1 : 0);
}
}
private static class Value {
private final Peer peer;
private final long time;
Value(Peer peer, long time) {
this.peer = peer;
this.time = time;
}
Peer getPeer() {
return peer;
}
long getTime() {
return time;
}
}
private Daemon daemon;
/** A map for per user per datanode. */
private final LinkedListMultimap<Key, Value> multimap =
LinkedListMultimap.create();
private final int capacity;
private final long expiryPeriod;
private static PeerCache instance = null;
@VisibleForTesting
PeerCache(int c, long e) {
this.capacity = c;
this.expiryPeriod = e;
if (capacity == 0 ) {
LOG.info("SocketCache disabled.");
}
else if (expiryPeriod == 0) {
throw new IllegalStateException("Cannot initialize expiryPeriod to " +
expiryPeriod + "when cache is enabled.");
}
}
public static synchronized PeerCache getInstance(int c, long e) {
// capacity is only initialized once
if (instance == null) {
instance = new PeerCache(c, e);
} else { //already initialized once
if (instance.capacity != c || instance.expiryPeriod != e) {
LOG.info("capacity and expiry periods already set to " +
instance.capacity + " and " + instance.expiryPeriod +
" respectively. Cannot set it to " + c + " and " + e);
}
}
return instance;
}
private boolean isDaemonStarted() {
return (daemon == null)? false: true;
}
private synchronized void startExpiryDaemon() {
// start daemon only if not already started
if (isDaemonStarted() == true) {
return;
}
daemon = new Daemon(new Runnable() {
@Override
public void run() {
try {
PeerCache.this.run();
} catch(InterruptedException e) {
//noop
} finally {
PeerCache.this.clear();
}
}
@Override
public String toString() {
return String.valueOf(PeerCache.this);
}
});
daemon.start();
}
/**
* Get a cached peer connected to the given DataNode.
* @param dnId The DataNode to get a Peer for.
* @param isDomain Whether to retrieve a DomainPeer or not.
*
* @return An open Peer connected to the DN, or null if none
* was found.
*/
public synchronized Peer get(DatanodeID dnId, boolean isDomain) {
if (capacity <= 0) { // disabled
return null;
}
List<Value> sockStreamList = multimap.get(new Key(dnId, isDomain));
if (sockStreamList == null) {
return null;
}
Iterator<Value> iter = sockStreamList.iterator();
while (iter.hasNext()) {
Value candidate = iter.next();
iter.remove();
if (!candidate.getPeer().isClosed()) {
return candidate.getPeer();
}
}
return null;
}
/**
* Give an unused socket to the cache.
* @param sock socket not used by anyone.
*/
public synchronized void put(DatanodeID dnId, Peer peer) {
Preconditions.checkNotNull(dnId);
Preconditions.checkNotNull(peer);
if (peer.isClosed()) return;
if (capacity <= 0) {
// Cache disabled.
IOUtils.cleanup(LOG, peer);
return;
}
startExpiryDaemon();
if (capacity == multimap.size()) {
evictOldest();
}
multimap.put(new Key(dnId, peer.getDomainSocket() != null),
new Value(peer, Time.monotonicNow()));
}
public synchronized int size() {
return multimap.size();
}
/**
* Evict and close sockets older than expiry period from the cache.
*/
private synchronized void evictExpired(long expiryPeriod) {
while (multimap.size() != 0) {
Iterator<Entry<Key, Value>> iter =
multimap.entries().iterator();
Entry<Key, Value> entry = iter.next();
// if oldest socket expired, remove it
if (entry == null ||
Time.monotonicNow() - entry.getValue().getTime() <
expiryPeriod) {
break;
}
IOUtils.cleanup(LOG, entry.getValue().getPeer());
iter.remove();
}
}
/**
* Evict the oldest entry in the cache.
*/
private synchronized void evictOldest() {
// We can get the oldest element immediately, because of an interesting
// property of LinkedListMultimap: its iterator traverses entries in the
// order that they were added.
Iterator<Entry<Key, Value>> iter =
multimap.entries().iterator();
if (!iter.hasNext()) {
throw new IllegalStateException("Cannot evict from empty cache! " +
"capacity: " + capacity);
}
Entry<Key, Value> entry = iter.next();
IOUtils.cleanup(LOG, entry.getValue().getPeer());
iter.remove();
}
/**
* Periodically check in the cache and expire the entries
* older than expiryPeriod minutes
*/
private void run() throws InterruptedException {
for(long lastExpiryTime = Time.monotonicNow();
!Thread.interrupted();
Thread.sleep(expiryPeriod)) {
final long elapsed = Time.monotonicNow() - lastExpiryTime;
if (elapsed >= expiryPeriod) {
evictExpired(expiryPeriod);
lastExpiryTime = Time.monotonicNow();
}
}
clear();
throw new InterruptedException("Daemon Interrupted");
}
/**
* Empty the cache, and close all sockets.
*/
@VisibleForTesting
synchronized void clear() {
for (Value value : multimap.values()) {
IOUtils.cleanup(LOG, value.getPeer());
}
multimap.clear();
}
@VisibleForTesting
void close() {
clear();
if (daemon != null) {
daemon.interrupt();
try {
daemon.join();
} catch (InterruptedException e) {
throw new RuntimeException("failed to join thread");
}
}
daemon = null;
}
}