/*
* 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.ignite.cache.eviction.fifo;
import java.util.Collection;
import java.util.Collections;
import org.apache.ignite.cache.eviction.AbstractEvictionPolicy;
import org.apache.ignite.cache.eviction.EvictableEntry;
import org.apache.ignite.internal.util.typedef.internal.S;
import org.apache.ignite.mxbean.IgniteMBeanAware;
import org.jsr166.ConcurrentLinkedDeque8;
import org.jsr166.ConcurrentLinkedDeque8.Node;
/**
* Eviction policy based on {@code First In First Out (FIFO)} algorithm and supports batch eviction.
* <p>
* The eviction starts in the following cases:
* <ul>
* <li>The cache size becomes {@code batchSize} elements greater than the maximum size.</li>
* <li>
* The size of cache entries in bytes becomes greater than the maximum memory size.
* The size of cache entry calculates as sum of key size and value size.
* </li>
* </ul>
* <b>Note:</b>Batch eviction is enabled only if maximum memory limit isn't set ({@code maxMemSize == 0}).
* {@code batchSize} elements will be evicted in this case. The default {@code batchSize} value is {@code 1}.
* <p>
* This implementation is very efficient since it does not create any additional
* table-like data structures. The {@code FIFO} ordering information is
* maintained by attaching ordering metadata to cache entries.
*/
public class FifoEvictionPolicy<K, V> extends AbstractEvictionPolicy<K, V> implements IgniteMBeanAware {
/** */
private static final long serialVersionUID = 0L;
/** FIFO queue. */
private final ConcurrentLinkedDeque8<EvictableEntry<K, V>> queue =
new ConcurrentLinkedDeque8<>();
/**
* Constructs FIFO eviction policy with all defaults.
*/
public FifoEvictionPolicy() {
// No-op.
}
/**
* Constructs FIFO eviction policy with maximum size. Empty entries are allowed.
*
* @param max Maximum allowed size of cache before entry will start getting evicted.
*/
public FifoEvictionPolicy(int max) {
setMaxSize(max);
}
/**
* Constructs FIFO eviction policy with maximum size and given batch size. Empty entries are allowed.
*
* @param max Maximum allowed size of cache before entry will start getting evicted.
* @param batchSize Batch size.
*/
public FifoEvictionPolicy(int max, int batchSize) {
setMaxSize(max);
setBatchSize(batchSize);
}
/** {@inheritDoc} */
@Override public int getCurrentSize() {
return queue.sizex();
}
/** {@inheritDoc} */
@Override public FifoEvictionPolicy<K, V> setMaxMemorySize(long maxMemSize) {
super.setMaxMemorySize(maxMemSize);
return this;
}
/** {@inheritDoc} */
@Override public FifoEvictionPolicy<K, V> setMaxSize(int max) {
super.setMaxSize(max);
return this;
}
/** {@inheritDoc} */
@Override public FifoEvictionPolicy<K, V> setBatchSize(int batchSize) {
super.setBatchSize(batchSize);
return this;
}
/**
* Gets read-only view on internal {@code FIFO} queue in proper order.
*
* @return Read-only view ono internal {@code 'FIFO'} queue.
*/
public Collection<EvictableEntry<K, V>> queue() {
return Collections.unmodifiableCollection(queue);
}
/** {@inheritDoc} */
@SuppressWarnings("unchecked")
@Override protected boolean removeMeta(Object meta) {
return queue.unlinkx((Node<EvictableEntry<K, V>>)meta);
}
/**
* @param entry Entry to touch.
* @return {@code True} if queue has been changed by this call.
*/
protected boolean touch(EvictableEntry<K, V> entry) {
Node<EvictableEntry<K, V>> node = entry.meta();
// Entry has not been enqueued yet.
if (node == null) {
while (true) {
node = queue.offerLastx(entry);
if (entry.putMetaIfAbsent(node) != null) {
// Was concurrently added, need to clear it from queue.
queue.unlinkx(node);
// Queue has not been changed.
return false;
}
else if (node.item() != null) {
if (!entry.isCached()) {
// Was concurrently evicted, need to clear it from queue.
queue.unlinkx(node);
return false;
}
memSize.add(entry.size());
return true;
}
// If node was unlinked by concurrent shrink() call, we must repeat the whole cycle.
else if (!entry.removeMeta(node))
return false;
}
}
// Entry is already in queue.
return false;
}
/**
* Tries to remove one item from queue.
*
* @return number of bytes that was free. {@code -1} if queue is empty.
*/
@Override protected int shrink0() {
EvictableEntry<K, V> entry = queue.poll();
if (entry == null)
return -1;
int size = 0;
Node<EvictableEntry<K, V>> meta = entry.removeMeta();
if (meta != null) {
size = entry.size();
memSize.add(-size);
if (!entry.evict())
touch(entry);
}
return size;
}
/** {@inheritDoc} */
@Override public Object getMBean() {
return new FifoEvictionPolicyMBeanImpl();
}
/** {@inheritDoc} */
@Override public String toString() {
return S.toString(FifoEvictionPolicy.class, this);
}
/**
* MBean implementation for FifoEvictionPolicy.
*/
private class FifoEvictionPolicyMBeanImpl implements FifoEvictionPolicyMBean {
/** {@inheritDoc} */
@Override public long getCurrentMemorySize() {
return FifoEvictionPolicy.this.getCurrentMemorySize();
}
/** {@inheritDoc} */
@Override public int getCurrentSize() {
return FifoEvictionPolicy.this.getCurrentSize();
}
/** {@inheritDoc} */
@Override public int getMaxSize() {
return FifoEvictionPolicy.this.getMaxSize();
}
/** {@inheritDoc} */
@Override public void setMaxSize(int max) {
FifoEvictionPolicy.this.setMaxSize(max);
}
/** {@inheritDoc} */
@Override public int getBatchSize() {
return FifoEvictionPolicy.this.getBatchSize();
}
/** {@inheritDoc} */
@Override public void setBatchSize(int batchSize) {
FifoEvictionPolicy.this.setBatchSize(batchSize);
}
/** {@inheritDoc} */
@Override public long getMaxMemorySize() {
return FifoEvictionPolicy.this.getMaxMemorySize();
}
/** {@inheritDoc} */
@Override public void setMaxMemorySize(long maxMemSize) {
FifoEvictionPolicy.this.setMaxMemorySize(maxMemSize);
}
}
}