package com.avaje.ebeaninternal.server.cache;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import com.avaje.ebean.BackgroundExecutor;
import com.avaje.ebean.EbeanServer;
import com.avaje.ebean.cache.ServerCache;
import com.avaje.ebean.cache.ServerCacheOptions;
import com.avaje.ebean.cache.ServerCacheStatistics;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* The default cache implementation.
* <p>
* It is base on ConcurrentHashMap with periodic trimming using a TimerTask.
* The periodic trimming means that an LRU list does not have to be maintained.
* </p>
*/
public class DefaultServerCache implements ServerCache {
private static final Logger logger = LoggerFactory.getLogger(DefaultServerCache.class);
private static final CacheEntryComparator comparator = new CacheEntryComparator();
private final ConcurrentHashMap<Object, CacheEntry> map = new ConcurrentHashMap<Object, CacheEntry>();
private final AtomicInteger missCount = new AtomicInteger();
private final AtomicInteger removedHitCount = new AtomicInteger();
private final Object monitor = new Object();
private final String name;
private int maxSize;
private long trimFrequency;
private int maxIdleSecs;
private int maxSecsToLive;
public DefaultServerCache(String name, ServerCacheOptions options) {
this(name, options.getMaxSize(), options.getMaxIdleSecs(), options.getMaxSecsToLive());
}
public DefaultServerCache(String name, int maxSize, int maxIdleSecs, int maxSecsToLive) {
this.name = name;
this.maxSize = maxSize;
this.maxIdleSecs = maxIdleSecs;
this.maxSecsToLive = maxSecsToLive;
this.trimFrequency = 60;
}
public void init(EbeanServer server) {
TrimTask trim = new TrimTask();
BackgroundExecutor executor = server.getBackgroundExecutor();
executor.executePeriodically(trim, trimFrequency, TimeUnit.SECONDS);
}
public ServerCacheStatistics getStatistics(boolean reset) {
ServerCacheStatistics s = new ServerCacheStatistics();
s.setCacheName(name);
s.setMaxSize(maxSize);
// these counters won't necessarily be consistent with
// respect to each other as activity can occur while
// they are being calculated
int mc = reset ? missCount.getAndSet(0) : missCount.get();
int hc = getHitCount(reset);
int size = size();
s.setSize(size);
s.setHitCount(hc);
s.setMissCount(mc);
return s;
}
public int getHitRatio() {
int mc = missCount.get();
int hc = getHitCount(false);
int totalCount = hc + mc;
if (totalCount == 0){
return 0;
} else {
return hc * 100 / totalCount;
}
}
private int getHitCount(boolean reset) {
int hc = reset ? removedHitCount.getAndSet(0) : removedHitCount.get();
for (CacheEntry cacheEntry : map.values()) {
hc += cacheEntry.getHitCount(reset);
}
return hc;
}
public ServerCacheOptions getOptions() {
synchronized (monitor) {
ServerCacheOptions o = new ServerCacheOptions();
o.setMaxIdleSecs(maxIdleSecs);
o.setMaxSize(maxSize);
o.setMaxSecsToLive(maxSecsToLive);
return o;
}
}
public void setOptions(ServerCacheOptions o) {
synchronized (monitor) {
maxIdleSecs = o.getMaxIdleSecs();
maxSize = o.getMaxSize();
maxSecsToLive = o.getMaxSecsToLive();
}
}
/**
* Return the max cache size.
*/
public int getMaxSize() {
return maxSize;
}
/**
* Set the max cache size.
*/
public void setMaxSize(int maxSize) {
synchronized (monitor) {
this.maxSize = maxSize;
}
}
/**
* Return the max idle time.
*/
public long getMaxIdleSecs() {
return maxIdleSecs;
}
/**
* Set the max idle time.
*/
public void setMaxIdleSecs(int maxIdleSecs) {
synchronized (monitor) {
this.maxIdleSecs = maxIdleSecs;
}
}
/**
* Return the maximum time to live.
*/
public long getMaxSecsToLive() {
return maxSecsToLive;
}
/**
* Set the maximum time to live.
*/
public void setMaxSecsToLive(int maxSecsToLive) {
synchronized (monitor) {
this.maxSecsToLive = maxSecsToLive;
}
}
/**
* Return the name of the cache.
*/
public String getName() {
return name;
}
/**
* Clear the cache.
*/
public void clear() {
map.clear();
}
/**
* Return a value from the cache.
*/
public Object get(Object key) {
CacheEntry entry = map.get(key);
if (entry == null){
missCount.incrementAndGet();
return null;
} else {
// get value incrementing last
// access time and hitCount
return entry.getValue();
}
}
/**
* Put a value into the cache.
*/
public Object put(Object key, Object value) {
// put new entry with create time
CacheEntry entry = map.put(key, new CacheEntry(key, value));
if (entry == null){
return null;
} else {
int removedHits = entry.getHitCount(true);
removedHitCount.addAndGet(removedHits);
return entry.getValue();
}
}
/**
* Put a value into the cache but only if absent.
*/
public Object putIfAbsent(Object key, Object value) {
CacheEntry entry = map.putIfAbsent(key, new CacheEntry(key, value));
if (entry == null){
return null;
} else {
return entry.getValue();
}
}
/**
* Remove an entry from the cache.
*/
public Object remove(Object key) {
CacheEntry entry = map.remove(key);
if (entry == null){
return null;
} else {
int removedHits = entry.getHitCount(true);
removedHitCount.addAndGet(removedHits);
return entry.getValue();
}
}
/**
* Return the number of elements in the cache.
*/
public int size() {
return map.size();
}
/**
* The task used to periodically trim the cache.
*/
private class TrimTask implements Runnable {
public void run() {
long startTime = System.currentTimeMillis();
if (logger.isTraceEnabled()){
logger.trace("trimming cache " + name);
}
int trimmedByIdle = 0;
int trimmedByTTL = 0;
int trimmedByLRU = 0;
boolean trimMaxSize = maxSize > 0 && maxSize < size();
ArrayList<CacheEntry> activeList = new ArrayList<CacheEntry>();
long idleExpire = System.currentTimeMillis() - (maxIdleSecs*1000);
long ttlExpire = System.currentTimeMillis() - (maxSecsToLive*1000);
Iterator<CacheEntry> it = map.values().iterator();
while (it.hasNext()) {
CacheEntry cacheEntry = it.next();
if (maxIdleSecs > 0 && idleExpire > cacheEntry.getLastAccessTime()) {
it.remove();
trimmedByIdle++;
} else if (maxSecsToLive > 0 && ttlExpire > cacheEntry.getCreateTime()) {
it.remove();
trimmedByTTL++;
} else if (trimMaxSize) {
activeList.add(cacheEntry);
}
}
if (trimMaxSize) {
trimmedByLRU = activeList.size() - maxSize;
if (trimmedByLRU > 0) {
// sort into last access time ascending
Collections.sort(activeList, comparator);
for (int i = maxSize; i < activeList.size(); i++) {
// remove if still in the cache
map.remove(activeList.get(i).getKey());
}
}
}
long exeTime = System.currentTimeMillis() - startTime;
if (logger.isDebugEnabled()){
logger.debug("Executed trim of cache " + name + " in ["+exeTime
+"]millis idle[" + trimmedByIdle + "] timeToLive["
+ trimmedByTTL + "] accessTime["
+ trimmedByLRU + "]");
}
}
}
/**
* Comparator for sorting by last access time.
*/
private static class CacheEntryComparator implements Comparator<CacheEntry>, Serializable {
private static final long serialVersionUID = 1L;
public int compare(CacheEntry o1, CacheEntry o2) {
return o1.getLastAccessLong().compareTo(o2.getLastAccessLong());
}
}
/**
* Wraps the values to additionally hold createTime and lastAccessTime.
*/
public static class CacheEntry {
private final Object key;
private final Object value;
private final long createTime;
private final AtomicInteger hitCount = new AtomicInteger();
private Long lastAccessTime;
public CacheEntry(Object key, Object value) {
this.key = key;
this.value = value;
this.createTime = System.currentTimeMillis();
this.lastAccessTime = Long.valueOf(createTime);
}
public Object getKey() {
return key;
}
public Object getValue() {
// object assignment is atomic
hitCount.incrementAndGet();
this.lastAccessTime = Long.valueOf(System.currentTimeMillis());
return value;
}
public long getCreateTime() {
return createTime;
}
public long getLastAccessTime() {
return lastAccessTime.longValue();
}
public Long getLastAccessLong() {
return lastAccessTime;
}
public int getHitCount(boolean reset) {
if (reset){
return hitCount.getAndSet(0);
} else {
return hitCount.get();
}
}
public int getHitCount() {
return hitCount.get();
}
}
}