package io.ebeaninternal.server.cache;
import io.ebean.BackgroundExecutor;
import io.ebean.cache.ServerCache;
import io.ebean.cache.ServerCacheOptions;
import io.ebean.cache.ServerCacheStatistics;
import io.ebean.cache.TenantAwareKey;
import io.ebean.config.CurrentTenantProvider;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.Serializable;
import java.util.List;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.LongAdder;
/**
* 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 {
protected static final Logger logger = LoggerFactory.getLogger(DefaultServerCache.class);
/**
* Compare by last access time (for LRU eviction).
*/
public static final CompareByLastAccess BY_LAST_ACCESS = new CompareByLastAccess();
/**
* The underlying map (ConcurrentHashMap or similar)
*/
protected final Map<Object, CacheEntry> map;
protected final LongAdder missCount = new LongAdder();
protected final LongAdder hitCount = new LongAdder();
protected final LongAdder insertCount = new LongAdder();
protected final LongAdder updateCount = new LongAdder();
protected final LongAdder removeCount = new LongAdder();
protected final LongAdder clearCount = new LongAdder();
protected final LongAdder evictByIdle = new LongAdder();
protected final LongAdder evictByTTL = new LongAdder();
protected final LongAdder evictByLRU = new LongAdder();
protected final LongAdder evictCount = new LongAdder();
protected final LongAdder evictMicros = new LongAdder();
protected final String name;
protected int maxSize;
protected final int trimFrequency;
protected int maxIdleSecs;
protected int maxSecsToLive;
protected TenantAwareKey tenantAwareKey;
/**
* Construct using a ConcurrentHashMap and cache options.
*/
public DefaultServerCache(String name, CurrentTenantProvider tenantProvider, ServerCacheOptions options) {
this(name, new ConcurrentHashMap<>(), tenantProvider, options);
}
/**
* Construct passing in name, map and base eviction controls as ServerCacheOptions.
*/
public DefaultServerCache(String name, Map<Object, CacheEntry> map, CurrentTenantProvider tenantProvider, ServerCacheOptions options) {
this(name, map, tenantProvider, options.getMaxSize(), options.getMaxIdleSecs(), options.getMaxSecsToLive(), options.getTrimFrequency());
}
/**
* Construct passing in name, map and base eviction controls.
*/
public DefaultServerCache(String name, Map<Object, CacheEntry> map, CurrentTenantProvider tenantProvider, int maxSize, int maxIdleSecs, int maxSecsToLive, int trimFrequency) {
this.name = name;
this.map = map;
this.maxSize = maxSize;
this.tenantAwareKey = new TenantAwareKey(tenantProvider);
this.maxIdleSecs = maxIdleSecs;
this.maxSecsToLive = maxSecsToLive;
this.trimFrequency = determineTrim(maxIdleSecs, maxSecsToLive, trimFrequency);
}
/**
* Determine a good trimFrequency as half of maxIdleSecs (or maxSecsToLive).
*/
int determineTrim(int maxIdleSecs, int maxSecsToLive, int trimFrequency) {
if (trimFrequency > 0) {
return trimFrequency;
}
if (maxIdleSecs > 0) {
return maxIdleSecs / 2 - 1;
}
if (maxSecsToLive > 0) {
return maxSecsToLive / 2 - 1;
}
return 0;
}
public void periodicTrim(BackgroundExecutor executor) {
EvictionRunnable trim = new EvictionRunnable();
// default to trimming the cache every 60 seconds
long trimFreqSecs = (trimFrequency == 0) ? 60 : trimFrequency;
executor.executePeriodically(trim, trimFreqSecs, TimeUnit.SECONDS);
}
@Override
public ServerCacheStatistics getStatistics(boolean reset) {
ServerCacheStatistics cacheStats = new ServerCacheStatistics();
cacheStats.setCacheName(name);
cacheStats.setMaxSize(maxSize);
// these counters won't necessarily be consistent with
// respect to each other as activity can occur while
// they are being calculated here but they should be good enough
// and we don't want to reduce concurrent use to make them consistent
long clear = reset ? clearCount.sumThenReset() : clearCount.sum();
long remove = reset ? removeCount.sumThenReset() : removeCount.sum();
long update = reset ? updateCount.sumThenReset() : updateCount.sum();
long insert = reset ? insertCount.sumThenReset() : insertCount.sum();
long miss = reset ? missCount.sumThenReset() : missCount.sum();
long hit = reset ? hitCount.sumThenReset() : hitCount.sum();
long evict = reset ? evictCount.sumThenReset() : evictCount.sum();
long evictTime = reset ? evictMicros.sumThenReset() : evictMicros.sum();
long evictIdle = reset ? evictByIdle.sumThenReset() : evictByIdle.sum();
long evictTTL = reset ? evictByTTL.sumThenReset() : evictByTTL.sum();
long evictLRU = reset ? evictByLRU.sumThenReset() : evictByLRU.sum();
int size = size();
cacheStats.setSize(size);
cacheStats.setHitCount(hit);
cacheStats.setMissCount(miss);
cacheStats.setInsertCount(insert);
cacheStats.setUpdateCount(update);
cacheStats.setRemoveCount(remove);
cacheStats.setClearCount(clear);
cacheStats.setEvictionRunCount(evict);
cacheStats.setEvictionRunMicros(evictTime);
cacheStats.setEvictByIdle(evictIdle);
cacheStats.setEvictByTTL(evictTTL);
cacheStats.setEvictByLRU(evictLRU);
return cacheStats;
}
@Override
public int getHitRatio() {
long mc = missCount.sum();
long hc = hitCount.sum();
long totalCount = hc + mc;
if (totalCount == 0) {
return 0;
} else {
return (int) (hc * 100 / totalCount);
}
}
/**
* Return the name of the cache.
*/
public String getName() {
return name;
}
/**
* Clear the cache.
*/
@Override
public void clear() {
clearCount.increment();
map.clear();
}
/**
* Return the tenant aware key.
*/
private Object key(Object id) {
return tenantAwareKey.key(id);
}
/**
* Return a value from the cache.
*/
@Override
public Object get(Object id) {
CacheEntry entry = map.get(key(id));
if (entry == null) {
missCount.increment();
return null;
} else {
// Important that hitCount.increment() MUST be low latency under concurrent
// use hence must use LongAdder or better here
hitCount.increment();
return entry.getValue();
}
}
/**
* Put a value into the cache.
*/
@Override
public Object put(Object id, Object value) {
Object key = key(id);
CacheEntry entry = map.put(key, new CacheEntry(key, value));
if (entry == null) {
insertCount.increment();
return null;
} else {
updateCount.increment();
return entry.getValue();
}
}
/**
* Remove an entry from the cache.
*/
@Override
public Object remove(Object id) {
CacheEntry entry = map.remove(key(id));
if (entry == null) {
return null;
} else {
removeCount.increment();
return entry.getValue();
}
}
/**
* Return the number of elements in the cache.
*/
@Override
public int size() {
return map.size();
}
/**
* Return the size to trim to based on the max size.
* <p>
* This returns 90% of the max size.
* </p>
*/
protected int getTrimSize() {
return (maxSize * 90 / 100);
}
/**
* Run the eviction based on Idle time, Time to live and LRU last access.
*/
public void runEviction() {
long trimForMaxSize;
if (maxSize == 0) {
trimForMaxSize = 0;
} else {
trimForMaxSize = size() - maxSize;
}
if (maxIdleSecs == 0 && maxSecsToLive == 0 && trimForMaxSize < 0) {
// nothing to trim on this cache
return;
}
long startNanos = System.nanoTime();
long trimmedByIdle = 0;
long trimmedByTTL = 0;
long trimmedByLRU = 0;
List<CacheEntry> activeList = new ArrayList<>(map.size());
long idleExpireNano = startNanos - TimeUnit.SECONDS.toNanos(maxIdleSecs);
long ttlExpireNano = startNanos - TimeUnit.SECONDS.toNanos(maxSecsToLive);
Iterator<CacheEntry> it = map.values().iterator();
while (it.hasNext()) {
CacheEntry cacheEntry = it.next();
if (maxIdleSecs > 0 && idleExpireNano > cacheEntry.getLastAccessTime()) {
it.remove();
trimmedByIdle++;
} else if (maxSecsToLive > 0 && ttlExpireNano > cacheEntry.getCreateTime()) {
it.remove();
trimmedByTTL++;
} else if (trimForMaxSize > 0) {
activeList.add(cacheEntry);
}
}
if (trimForMaxSize > 0) {
trimmedByLRU = activeList.size() - maxSize;
if (trimmedByLRU > 0) {
// sort into last access time ascending
activeList.sort(BY_LAST_ACCESS);
int trimSize = getTrimSize();
for (int i = trimSize; i < activeList.size(); i++) {
// remove if still in the cache
map.remove(activeList.get(i).getKey());
}
}
}
long exeNanos = System.nanoTime() - startNanos;
long exeMicros = TimeUnit.MICROSECONDS.convert(exeNanos, TimeUnit.NANOSECONDS);
// increment the eviction statistics
evictMicros.add(exeMicros);
evictCount.increment();
evictByIdle.add(trimmedByIdle);
evictByTTL.add(trimmedByTTL);
evictByLRU.add(trimmedByLRU);
if (logger.isTraceEnabled()) {
logger.trace("Executed trim of cache {} in [{}]millis idle[{}] timeToLive[{}] accessTime[{}]"
, name, exeMicros, trimmedByIdle, trimmedByTTL, trimmedByLRU);
}
}
/**
* Runnable that calls the eviction routine.
*/
public class EvictionRunnable implements Runnable {
@Override
public void run() {
runEviction();
}
}
/**
* Comparator for sorting by last access time.
*/
public static class CompareByLastAccess implements Comparator<CacheEntry>, Serializable {
private static final long serialVersionUID = 1L;
@Override
public int compare(CacheEntry entry1, CacheEntry entry2) {
long x = entry1.getLastAccessTime();
long y = entry2.getLastAccessTime();
return (x < y) ? -1 : ((x == y) ? 0 : 1);
}
}
/**
* Wraps the value to additionally hold createTime and lastAccessTime and hit counter.
*/
public static class CacheEntry {
private final Object key;
private final Object value;
private final long createTime;
private long lastAccessTime;
public CacheEntry(Object key, Object value) {
this.key = key;
this.value = value;
this.createTime = System.nanoTime();
this.lastAccessTime = createTime;
}
/**
* Return the entry key.
*/
public Object getKey() {
return key;
}
/**
* Return the entry value.
*/
public Object getValue() {
// long assignment should be atomic these days (Ref Cliff Click)
lastAccessTime = System.nanoTime();
return value;
}
/**
* Return the time the entry was created.
*/
public long getCreateTime() {
return createTime;
}
/**
* Return the time the entry was last accessed.
*/
public long getLastAccessTime() {
return lastAccessTime;
}
}
}