package org.act.tstream.utils;
import java.util.Deque;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Map;
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();
public RotatingMap(int numBuckets, ExpiredCallback<K, V> callback, boolean isSingleThread) {
if (numBuckets < 2) {
throw new IllegalArgumentException("numBuckets must be >= 2");
}
if (isSingleThread == true) {
_buckets = new LinkedList<Map<K, V>>();
}else {
_buckets = new LinkedBlockingDeque<Map<K, V>>();
}
for (int i = 0; i < numBuckets; i++) {
_buckets.add(new ConcurrentHashMap<K, V>());
}
_callback = callback;
}
public RotatingMap(ExpiredCallback<K, V> callback) {
this(DEFAULT_NUM_BUCKETS, callback, false);
}
public RotatingMap(int numBuckets) {
this(numBuckets, null, false);
}
public Map<K, V> rotate() {
Map<K, V> dead = _buckets.removeLast();
_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;
}
@Override
public V get(K key) {
for (Map<K, V> bucket : _buckets) {
if (bucket.containsKey(key)) {
return bucket.get(key);
}
}
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);
}
}
/**
* Remove item from Rotate
*
* On the side of performance, scanning from header is faster On the side of
* logic, it should scan from the end to first.
*
* @param key
* @return
*/
@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;
}
}