/**
* 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 com.alibaba.jstorm.utils;
import java.util.*;
import java.util.Map.Entry;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.LinkedBlockingDeque;
/**
* RotatingMap must be used under thread-safe environment
*
* Expires keys that have not been updated in the configured number of seconds.
* The algorithm used will take between expirationSecs and expirationSecs * (1 + 1/ (numBuckets-1))
* to actually expire the message.
*
* get, put, remove, containsKey, and size take O(numBuckets) time to run.
*/
public class RotatingMap<K, V> implements TimeOutMap<K, V> {
// this default ensures things expire at most 50% past the expiration time
private static final int DEFAULT_NUM_BUCKETS = 3;
private Deque<Map<K, V>> buckets;
private ExpiredCallback callback;
private final Object lock = new Object();
private boolean isSingleThread;
public RotatingMap(int numBuckets, ExpiredCallback<K, V> callback, boolean isSingleThread) {
this.isSingleThread = isSingleThread;
if (numBuckets < 2) {
throw new IllegalArgumentException("numBuckets must be >= 2");
}
if (isSingleThread) {
buckets = new LinkedList<>();
for (int i = 0; i < numBuckets; i++) {
buckets.add(new HashMap<K, V>());
}
} else {
buckets = new LinkedBlockingDeque<>();
for (int i = 0; i < numBuckets; i++) {
buckets.add(new ConcurrentHashMap<K, V>());
}
}
this.callback = callback;
}
public RotatingMap(ExpiredCallback<K, V> callback) {
this(DEFAULT_NUM_BUCKETS, callback, false);
}
public RotatingMap(int numBuckets) {
this(numBuckets, null, false);
}
public RotatingMap(int numBuckets, boolean isSingleThread) {
this(numBuckets, null, isSingleThread);
}
public Map<K, V> rotate() {
Map<K, V> dead = buckets.removeLast();
if (isSingleThread) {
buckets.addFirst(new HashMap<K, V>());
} else {
buckets.addFirst(new ConcurrentHashMap<K, V>());
}
if (callback != null) {
for (Entry<K, V> entry : dead.entrySet()) {
callback.expire(entry.getKey(), entry.getValue());
}
}
return dead;
}
@Override
public boolean containsKey(K key) {
for (Map<K, V> bucket : buckets) {
if (bucket.containsKey(key)) {
return true;
}
}
return false;
}
public Set<K> keySet() {
Set<K> keys = new HashSet<K>();
for (Map<K, V> bucket : buckets) {
keys.addAll(bucket.keySet());
}
return keys;
}
@Override
public V get(K key) {
for (Map<K, V> bucket : buckets) {
V v = bucket.get(key);
if (v != null) {
return v;
}
}
return null;
}
@Override
public void putHead(K key, V value) {
buckets.peekFirst().put(key, value);
}
@Override
public void put(K key, V value) {
Iterator<Map<K, V>> it = buckets.iterator();
Map<K, V> bucket = it.next();
bucket.put(key, value);
while (it.hasNext()) {
bucket = it.next();
bucket.remove(key);
}
}
/**
* On the side of performance, scanning from header is faster on the side of logic, it should scan from the end to first.
*/
@Override
public Object remove(K key) {
for (Map<K, V> bucket : buckets) {
Object value = bucket.remove(key);
if (value != null) {
return value;
}
}
return null;
}
@Override
public int size() {
int size = 0;
for (Map<K, V> bucket : buckets) {
size += bucket.size();
}
return size;
}
public void clear() {
for (Map<K, V> bucket : buckets) {
bucket.clear();
}
}
@Override
public String toString() {
return buckets.toString();
}
}