/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.nifi.distributed.cache.server.map;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.SortedMap;
import java.util.concurrent.ConcurrentSkipListMap;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.apache.nifi.distributed.cache.server.EvictionPolicy;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class SimpleMapCache implements MapCache {
private static final Logger logger = LoggerFactory.getLogger(SimpleMapCache.class);
private final Map<ByteBuffer, MapCacheRecord> cache = new HashMap<>();
private final SortedMap<MapCacheRecord, ByteBuffer> inverseCacheMap;
private final ReadWriteLock rwLock = new ReentrantReadWriteLock();
private final Lock readLock = rwLock.readLock();
private final Lock writeLock = rwLock.writeLock();
private final String serviceIdentifier;
private final int maxSize;
public SimpleMapCache(final String serviceIdentifier, final int maxSize, final EvictionPolicy evictionPolicy) {
// need to change to ConcurrentMap as this is modified when only the readLock is held
inverseCacheMap = new ConcurrentSkipListMap<>(evictionPolicy.getComparator());
this.serviceIdentifier = serviceIdentifier;
this.maxSize = maxSize;
}
@Override
public String toString() {
return "SimpleSetCache[service id=" + serviceIdentifier + "]";
}
// don't need synchronized because this method is only called when the writeLock is held, and all
// public methods obtain either the read or write lock
private MapCacheRecord evict() {
if (cache.size() < maxSize) {
return null;
}
final MapCacheRecord recordToEvict = inverseCacheMap.firstKey();
final ByteBuffer valueToEvict = inverseCacheMap.remove(recordToEvict);
cache.remove(valueToEvict);
if (logger.isDebugEnabled()) {
logger.debug("Evicting value {} from cache", new String(valueToEvict.array(), StandardCharsets.UTF_8));
}
return recordToEvict;
}
@Override
public MapPutResult putIfAbsent(final ByteBuffer key, final ByteBuffer value) {
writeLock.lock();
try {
final MapCacheRecord record = cache.get(key);
if (record == null) {
// Record is null. We will add.
return put(key, value, record);
}
// Record is not null. Increment hit count and return result indicating that record was not added.
inverseCacheMap.remove(record);
record.hit();
inverseCacheMap.put(record, key);
return new MapPutResult(false, record, record, null);
} finally {
writeLock.unlock();
}
}
private MapPutResult put(final ByteBuffer key, final ByteBuffer value, final MapCacheRecord existing) {
// evict if we need to in order to make room for a new entry.
final MapCacheRecord evicted = evict();
final long revision;
if (existing == null) {
revision = 0;
} else {
revision = existing.getRevision() + 1;
inverseCacheMap.remove(existing);
}
final MapCacheRecord record = new MapCacheRecord(key, value, revision);
cache.put(key, record);
inverseCacheMap.put(record, key);
return new MapPutResult(true, record, existing, evicted);
}
@Override
public MapPutResult put(final ByteBuffer key, final ByteBuffer value) throws IOException {
writeLock.lock();
try {
final MapCacheRecord existing = cache.get(key);
return put(key, value, existing);
} finally {
writeLock.unlock();
}
}
@Override
public boolean containsKey(final ByteBuffer key) {
readLock.lock();
try {
final MapCacheRecord record = cache.get(key);
if (record == null) {
return false;
}
inverseCacheMap.remove(record);
record.hit();
inverseCacheMap.put(record, key);
return true;
} finally {
readLock.unlock();
}
}
@Override
public ByteBuffer get(final ByteBuffer key) {
readLock.lock();
try {
final MapCacheRecord record = cache.get(key);
if (record == null) {
return null;
}
inverseCacheMap.remove(record);
record.hit();
inverseCacheMap.put(record, key);
return record.getValue();
} finally {
readLock.unlock();
}
}
@Override
public ByteBuffer remove(ByteBuffer key) throws IOException {
writeLock.lock();
try {
final MapCacheRecord record = cache.remove(key);
if (record == null) {
return null;
}
inverseCacheMap.remove(record);
return record.getValue();
} finally {
writeLock.unlock();
}
}
@Override
public Map<ByteBuffer, ByteBuffer> removeByPattern(String regex) throws IOException {
writeLock.lock();
try {
final Map<ByteBuffer, ByteBuffer> removedMap = new HashMap<>();
final List<MapCacheRecord> removedRecords = new ArrayList<>();
Pattern p = Pattern.compile(regex);
for (ByteBuffer key : cache.keySet()) {
// Key must be backed by something that array() returns a byte[] that can be converted into a String via the default charset
Matcher m = p.matcher(new String(key.array()));
if (m.matches()) {
removedRecords.add(cache.get(key));
}
}
removedRecords.forEach((record) -> {
cache.remove(record.getKey());
inverseCacheMap.remove(record);
removedMap.put(record.getKey(), record.getValue());
});
return removedMap;
} finally {
writeLock.unlock();
}
}
@Override
public MapCacheRecord fetch(ByteBuffer key) throws IOException {
readLock.lock();
try {
final MapCacheRecord record = cache.get(key);
if (record == null) {
return null;
}
inverseCacheMap.remove(record);
record.hit();
inverseCacheMap.put(record, key);
return record;
} finally {
readLock.unlock();
}
}
@Override
public MapPutResult replace(MapCacheRecord inputRecord) throws IOException {
writeLock.lock();
try {
final ByteBuffer key = inputRecord.getKey();
final ByteBuffer value = inputRecord.getValue();
final MapCacheRecord existing = fetch(key);
if (existing != null && inputRecord.getRevision() != existing.getRevision()) {
// The key has been updated by other operation.
return new MapPutResult(false, inputRecord, existing, null);
}
return put(key, value, existing);
} finally {
writeLock.unlock();
}
}
@Override
public void shutdown() throws IOException {
}
}