package org.act.tstream.utils;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Map;
import java.util.Map.Entry;
/**
* 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 TimeCacheMap<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 LinkedList<HashMap<K, V>> _buckets;
private final Object _lock = new Object();
private Thread _cleaner;
private ExpiredCallback _callback;
public TimeCacheMap(int expirationSecs, int numBuckets,
ExpiredCallback<K, V> callback) {
if (numBuckets < 2) {
throw new IllegalArgumentException("numBuckets must be >= 2");
}
_buckets = new LinkedList<HashMap<K, V>>();
for (int i = 0; i < numBuckets; i++) {
_buckets.add(new HashMap<K, V>());
}
_callback = callback;
final long expirationMillis = expirationSecs * 1000L;
final long sleepTime = expirationMillis / (numBuckets - 1);
_cleaner = new Thread(new Runnable() {
public void run() {
while (true) {
Map<K, V> dead = null;
JStormUtils.sleepMs(sleepTime);
synchronized (_lock) {
dead = _buckets.removeLast();
_buckets.addFirst(new HashMap<K, V>());
}
if (_callback != null) {
for (Entry<K, V> entry : dead.entrySet()) {
_callback.expire(entry.getKey(), entry.getValue());
}
}
}
}
});
_cleaner.setDaemon(true);
_cleaner.start();
}
public TimeCacheMap(int expirationSecs, ExpiredCallback<K, V> callback) {
this(expirationSecs, DEFAULT_NUM_BUCKETS, callback);
}
public TimeCacheMap(int expirationSecs) {
this(expirationSecs, DEFAULT_NUM_BUCKETS);
}
public TimeCacheMap(int expirationSecs, int numBuckets) {
this(expirationSecs, numBuckets, null);
}
@Override
public boolean containsKey(K key) {
synchronized (_lock) {
for (HashMap<K, V> bucket : _buckets) {
if (bucket.containsKey(key)) {
return true;
}
}
return false;
}
}
@Override
public V get(K key) {
synchronized (_lock) {
for (HashMap<K, V> bucket : _buckets) {
if (bucket.containsKey(key)) {
return bucket.get(key);
}
}
return null;
}
}
@Override
public void putHead(K key, V value) {
synchronized (_lock) {
_buckets.getFirst().put(key, value);
}
}
@Override
public void put(K key, V value) {
synchronized (_lock) {
Iterator<HashMap<K, V>> it = _buckets.iterator();
HashMap<K, V> bucket = it.next();
bucket.put(key, value);
while (it.hasNext()) {
bucket = it.next();
bucket.remove(key);
}
}
}
@Override
public Object remove(K key) {
synchronized (_lock) {
for (HashMap<K, V> bucket : _buckets) {
if (bucket.containsKey(key)) {
return bucket.remove(key);
}
}
return null;
}
}
@Override
public int size() {
synchronized (_lock) {
int size = 0;
for (HashMap<K, V> bucket : _buckets) {
size += bucket.size();
}
return size;
}
}
public void cleanup() {
_cleaner.interrupt();
}
}