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package com.hazelcast.map;
import static com.hazelcast.map.eviction.EvictionHelper.checkEvictable;
import static com.hazelcast.map.eviction.EvictionHelper.evictableSize;
import static com.hazelcast.map.eviction.EvictionHelper.fireEvent;
import static com.hazelcast.map.eviction.EvictionHelper.removeEvictableRecords;
import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.concurrent.TimeUnit;
import com.hazelcast.config.MapConfig;
import com.hazelcast.map.record.Record;
import com.hazelcast.nio.serialization.Data;
/**
* Contains eviction specific functionality.
*/
abstract class AbstractEvictableRecordStore extends AbstractRecordStore {
/**
* Number of reads before clean up.
* A nice number such as 2^n - 1.
*/
protected static final int POST_READ_CHECK_POINT = 63;
/**
* Flag for checking if this record store has at least one candidate entry
* for expiration (idle or tll) or not.
*/
protected volatile boolean expirable;
/**
* Iterates over a pre-set entry count/percentage in one round.
* Used in expiration logic for traversing entries. Initializes lazily.
*/
protected Iterator expirationIterator;
/**
* If there is no clean-up caused by puts after some time,
* count a number of gets and start eviction.
*/
protected int readCountBeforeCleanUp;
/**
* used in LRU eviction logic.
*/
protected long lruAccessSequenceNumber;
/**
* Last run time of cleanup operation.
*/
protected long lastEvictionTime;
private final boolean evictionEnabled;
private final long minEvictionCheckMillis;
protected AbstractEvictableRecordStore(MapContainer mapContainer, int partitionId) {
super(mapContainer, partitionId);
final MapConfig mapConfig = mapContainer.getMapConfig();
this.minEvictionCheckMillis = mapConfig.getMinEvictionCheckMillis();
this.evictionEnabled
= !MapConfig.EvictionPolicy.NONE.equals(mapConfig.getEvictionPolicy());
this.expirable = isRecordStoreExpirable();
}
private boolean isRecordStoreExpirable() {
return mapContainer.getMapConfig().getMaxIdleSeconds() > 0
|| mapContainer.getMapConfig().getTimeToLiveSeconds() > 0;
}
@Override
public void evictExpiredEntries(int percentage, boolean backup) {
final long now = getNow();
final int size = size();
final int maxIterationCount = getMaxIterationCount(size, percentage);
final int maxRetry = 3;
int loop = 0;
int evictedEntryCount = 0;
while (true) {
evictedEntryCount += evictExpiredEntriesInternal(maxIterationCount, now, backup);
if (evictedEntryCount >= maxIterationCount) {
break;
}
loop++;
if (loop > maxRetry) {
break;
}
}
}
@Override
public boolean isExpirable() {
return expirable;
}
/**
* Intended to put an upper bound to iterations. Used in evictions.
*
* @param size of iterate-able.
* @param percentage percentage of size.
* @return 100 If calculated iteration count is less than 100, otherwise returns calculated iteration count.
*/
private int getMaxIterationCount(int size, int percentage) {
final int defaultMaxIterationCount = 100;
final float oneHundred = 100F;
float maxIterationCount = size * (percentage / oneHundred);
if (maxIterationCount <= defaultMaxIterationCount) {
return defaultMaxIterationCount;
}
return Math.round(maxIterationCount);
}
private int evictExpiredEntriesInternal(int maxIterationCount, long now, boolean backup) {
int evictedCount = 0;
int checkedEntryCount = 0;
initExpirationIterator();
while (expirationIterator.hasNext()) {
if (checkedEntryCount >= maxIterationCount) {
break;
}
checkedEntryCount++;
final Record record = expirationIterator.next();
final Data key = record.getKey();
if (isLocked(key)) {
continue;
}
if (isReachable(record, now)) {
continue;
}
//!!! get entry value here because evictInternal(key) nulls the record value.
final Object value = record.getValue();
evictInternal(key, backup);
evictedCount++;
// do post eviction operations if this partition is an owner partition.
if (!backup) {
doPostEvictionOperations(key, value, backup);
}
}
return evictedCount;
}
private void initExpirationIterator() {
if (expirationIterator == null || !expirationIterator.hasNext()) {
expirationIterator = records.values().iterator();
}
}
protected void resetAccessSequenceNumber() {
lruAccessSequenceNumber = 0L;
}
/**
* TODO make checkEvictable fast by carrying threshold logic to partition.
* This cleanup adds some latency to write operations.
* But it sweeps records much better under high write loads.
*
*
* @param now now in time.
*/
protected void evictEntries(long now, boolean backup) {
if (evictionEnabled) {
cleanUp(now, backup);
}
}
/**
* If there is no clean-up caused by puts after some time,
* try to clean-up from gets.
*
* @param now now.
*/
protected void postReadCleanUp(long now, boolean backup) {
if (evictionEnabled) {
readCountBeforeCleanUp++;
if ((readCountBeforeCleanUp & POST_READ_CHECK_POINT) == 0) {
cleanUp(now, backup);
}
}
}
/**
* Makes eviction clean-up logic.
*
* @param now now in millis.
* @param backup true if running on a backup partition, otherwise false
*/
private void cleanUp(long now, boolean backup) {
if (size() == 0) {
return;
}
if (shouldEvict(now)) {
removeEvictables(backup);
lastEvictionTime = now;
readCountBeforeCleanUp = 0;
}
}
protected boolean shouldEvict(long now) {
return evictionEnabled && inEvictableTimeWindow(now) && isEvictable();
}
private void removeEvictables(boolean backup) {
final int evictableSize = getEvictableSize();
if (evictableSize < 1) {
return;
}
final MapConfig mapConfig = mapContainer.getMapConfig();
removeEvictableRecords(this, evictableSize, mapConfig, mapServiceContext, backup);
}
private int getEvictableSize() {
final int size = size();
if (size < 1) {
return 0;
}
final int evictableSize = evictableSize(size, mapContainer.getMapConfig(), mapServiceContext);
if (evictableSize < 1) {
return 0;
}
return evictableSize;
}
/**
* Eviction waits at least {@link #minEvictionCheckMillis} milliseconds to run.
*
* @return true if in that time window,
* otherwise false
*/
private boolean inEvictableTimeWindow(long now) {
return minEvictionCheckMillis == 0L
|| (now - lastEvictionTime) > minEvictionCheckMillis;
}
private boolean isEvictable() {
return checkEvictable(mapContainer, partitionId);
}
protected void markRecordStoreExpirable(long ttl) {
if (ttl > 0L) {
expirable = true;
}
}
abstract Object evictInternal(Data key, boolean backup);
/**
* Check if record is reachable according to ttl or idle times.
* If not reachable return null.
*
* @param record {@link com.hazelcast.map.record.Record}
* @return null if evictable.
*/
protected Record getOrNullIfExpired(Record record, boolean backup) {
if (!expirable) {
return record;
}
if (record == null) {
return null;
}
final Data key = record.getKey();
if (isLocked(key)) {
return record;
}
if (isReachable(record)) {
return record;
}
final Object value = record.getValue();
evict(key, backup);
if (!backup) {
doPostEvictionOperations(key, value, backup);
}
return null;
}
private boolean isReachable(Record record) {
final long now = getNow();
return isReachable(record, now);
}
private boolean isReachable(Record record, long time) {
if (record == null) {
return false;
}
final Record idleExpired = isIdleExpired(record, time);
if (idleExpired == null) {
return false;
}
final Record ttlExpired = isTTLExpired(record, time);
return ttlExpired != null;
}
private Record isIdleExpired(Record record, long time) {
if (record == null) {
return null;
}
boolean result;
// lastAccessTime : updates on every touch (put/get).
final long lastAccessTime = record.getLastAccessTime();
assert lastAccessTime > 0L;
assert time > 0L;
assert time >= lastAccessTime;
final long idleTime = getIdleTime();
result = time - lastAccessTime >= idleTime;
return result ? null : record;
}
private long getIdleTime() {
final int maxIdleSeconds = mapContainer.getMapConfig().getMaxIdleSeconds();
return maxIdleSeconds == 0 ? Long.MAX_VALUE : mapServiceContext.convertTime(maxIdleSeconds, TimeUnit.SECONDS);
}
private Record isTTLExpired(Record record, long time) {
if (record == null) {
return null;
}
boolean result;
final long ttl = record.getTtl();
// when ttl is zero or negative, it should remain eternally.
if (ttl < 1L) {
return record;
}
final long creationTime = record.getCreationTime();
assert ttl > 0L : String.format("wrong ttl %d", ttl);
assert creationTime > 0L : String.format("wrong creationTime %d", creationTime);
assert time > 0L : String.format("wrong time %d", time);
assert time >= creationTime : String.format("time >= lastUpdateTime (%d >= %d)",
time, creationTime);
result = time - creationTime >= ttl;
return result ? null : record;
}
/**
* - Sends eviction event.
* - Invalidates near cache.
*
* @param key the key to be processed.
* @param value the value to be processed.
* @param backup true if running on a backup partition, otherwise false
*/
private void doPostEvictionOperations(Data key, Object value, boolean backup) {
if (backup) {
return;
}
final NearCacheProvider nearCacheProvider = mapServiceContext.getNearCacheProvider();
if (nearCacheProvider.isNearCacheAndInvalidationEnabled(name)) {
nearCacheProvider.invalidateAllNearCaches(name, key);
}
fireEvent(key, value, name, mapServiceContext);
}
protected void increaseRecordEvictionCriteriaNumber(Record record, MapConfig.EvictionPolicy evictionPolicy) {
switch (evictionPolicy) {
case LRU:
++lruAccessSequenceNumber;
record.setEvictionCriteriaNumber(lruAccessSequenceNumber);
break;
case LFU:
record.setEvictionCriteriaNumber(record.getEvictionCriteriaNumber() + 1L);
break;
case NONE:
break;
default:
throw new IllegalArgumentException("Not an appropriate eviction policy [" + evictionPolicy + ']');
}
}
@Override
protected void accessRecord(Record record, long now) {
super.accessRecord(record, now);
increaseRecordEvictionCriteriaNumber(record, mapContainer.getMapConfig().getEvictionPolicy());
}
/**
* Read only iterator. Iterates by checking whether a record expired or not.
*/
protected final class ReadOnlyRecordIterator implements Iterator {
private final Iterator iterator;
private Record nextRecord;
private Record lastReturned;
protected ReadOnlyRecordIterator(Collection values) {
this.iterator = values.iterator();
advance();
}
@Override
public boolean hasNext() {
return nextRecord != null;
}
@Override
public Record next() {
if (nextRecord == null) {
throw new NoSuchElementException();
}
lastReturned = nextRecord;
advance();
return lastReturned;
}
@Override
public void remove() {
throw new UnsupportedOperationException("remove not supported by this iterator");
}
private void advance() {
while (iterator.hasNext()) {
nextRecord = iterator.next();
boolean reachable = isReachable(nextRecord);
if (reachable && nextRecord != null) {
return;
}
}
nextRecord = null;
}
}
}
