org.elasticsearch.indices.IndicesRequestCache Maven / Gradle / Ivy
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/*
* Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
* or more contributor license agreements. Licensed under the Elastic License
* 2.0 and the Server Side Public License, v 1; you may not use this file except
* in compliance with, at your election, the Elastic License 2.0 or the Server
* Side Public License, v 1.
*/
package org.elasticsearch.indices;
import org.apache.lucene.index.DirectoryReader;
import org.apache.lucene.util.Accountable;
import org.apache.lucene.util.RamUsageEstimator;
import org.elasticsearch.common.CheckedSupplier;
import org.elasticsearch.common.bytes.BytesReference;
import org.elasticsearch.common.cache.Cache;
import org.elasticsearch.common.cache.CacheBuilder;
import org.elasticsearch.common.cache.CacheLoader;
import org.elasticsearch.common.cache.RemovalNotification;
import org.elasticsearch.common.lucene.index.ElasticsearchDirectoryReader;
import org.elasticsearch.common.settings.Setting;
import org.elasticsearch.common.settings.Setting.Property;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.common.unit.ByteSizeValue;
import org.elasticsearch.common.util.concurrent.ConcurrentCollections;
import org.elasticsearch.core.TimeValue;
import org.elasticsearch.index.mapper.MappingLookup;
import java.io.Closeable;
import java.io.IOException;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Objects;
import java.util.Set;
import java.util.concurrent.ConcurrentMap;
/**
* The indices request cache allows to cache a shard level request stage responses, helping with improving
* similar requests that are potentially expensive (because of aggs for example). The cache is fully coherent
* with the semantics of NRT (the index reader cache key is part of the cache key), and relies on size based
* eviction to evict old reader associated cache entries as well as scheduler reaper to clean readers that
* are no longer used or closed shards.
*
* Currently, the cache is only enabled for count requests, and can only be opted in on an index
* level setting that can be dynamically changed and defaults to false.
*
* There are still several TODOs left in this class, some easily addressable, some more complex, but the support
* is functional.
*/
public final class IndicesRequestCache implements Closeable {
/**
* A setting to enable or disable request caching on an index level. Its dynamic by default
* since we are checking on the cluster state IndexMetadata always.
*/
public static final Setting INDEX_CACHE_REQUEST_ENABLED_SETTING = Setting.boolSetting(
"index.requests.cache.enable",
true,
Property.Dynamic,
Property.IndexScope
);
public static final Setting INDICES_CACHE_QUERY_SIZE = Setting.memorySizeSetting(
"indices.requests.cache.size",
"1%",
Property.NodeScope
);
public static final Setting INDICES_CACHE_QUERY_EXPIRE = Setting.positiveTimeSetting(
"indices.requests.cache.expire",
new TimeValue(0),
Property.NodeScope
);
private final ConcurrentMap registeredClosedListeners = ConcurrentCollections.newConcurrentMap();
private final Set keysToClean = ConcurrentCollections.newConcurrentSet();
private final Cache cache;
IndicesRequestCache(Settings settings) {
TimeValue expire = INDICES_CACHE_QUERY_EXPIRE.exists(settings) ? INDICES_CACHE_QUERY_EXPIRE.get(settings) : null;
CacheBuilder cacheBuilder = CacheBuilder.builder()
.setMaximumWeight(INDICES_CACHE_QUERY_SIZE.get(settings).getBytes())
.weigher((k, v) -> k.ramBytesUsed() + v.ramBytesUsed())
.removalListener(notification -> notification.getKey().entity.onRemoval(notification));
if (expire != null) {
cacheBuilder.setExpireAfterAccess(expire);
}
cache = cacheBuilder.build();
}
@Override
public void close() {
cache.invalidateAll();
}
void clear(CacheEntity entity) {
keysToClean.add(new CleanupKey(entity, null));
cleanCache();
}
BytesReference getOrCompute(
CacheEntity cacheEntity,
CheckedSupplier loader,
MappingLookup.CacheKey mappingCacheKey,
DirectoryReader reader,
BytesReference cacheKey
) throws Exception {
final ESCacheHelper cacheHelper = ElasticsearchDirectoryReader.getESReaderCacheHelper(reader);
assert cacheHelper != null;
final Key key = new Key(cacheEntity, mappingCacheKey, cacheHelper.getKey(), cacheKey);
Loader cacheLoader = new Loader(cacheEntity, loader);
BytesReference value = cache.computeIfAbsent(key, cacheLoader);
if (cacheLoader.isLoaded()) {
key.entity.onMiss();
// see if its the first time we see this reader, and make sure to register a cleanup key
CleanupKey cleanupKey = new CleanupKey(cacheEntity, cacheHelper.getKey());
if (registeredClosedListeners.containsKey(cleanupKey) == false) {
Boolean previous = registeredClosedListeners.putIfAbsent(cleanupKey, Boolean.TRUE);
if (previous == null) {
cacheHelper.addClosedListener(cleanupKey);
}
}
/*
* Note that we don't use a closed listener for the mapping. Instead
* we let cache entries for out of date mappings age out. We do this
* because we don't reference count the MappingLookup so we can't tell
* when one is no longer used. Mapping updates should be a lot less
* frequent than reader closes so this is probably ok. On the other
* hand, for read only indices mapping changes are, well, possible,
* and readers are never changed. Oh well.
*/
} else {
key.entity.onHit();
}
return value;
}
/**
* Invalidates the given the cache entry for the given key and it's context
* @param cacheEntity the cache entity to invalidate for
* @param reader the reader to invalidate the cache entry for
* @param cacheKey the cache key to invalidate
*/
void invalidate(CacheEntity cacheEntity, MappingLookup.CacheKey mappingCacheKey, DirectoryReader reader, BytesReference cacheKey) {
assert reader.getReaderCacheHelper() != null;
cache.invalidate(new Key(cacheEntity, mappingCacheKey, reader.getReaderCacheHelper().getKey(), cacheKey));
}
private static class Loader implements CacheLoader {
private final CacheEntity entity;
private final CheckedSupplier loader;
private boolean loaded;
Loader(CacheEntity entity, CheckedSupplier loader) {
this.entity = entity;
this.loader = loader;
}
public boolean isLoaded() {
return this.loaded;
}
@Override
public BytesReference load(Key key) throws Exception {
BytesReference value = loader.get();
entity.onCached(key, value);
loaded = true;
return value;
}
}
/**
* Basic interface to make this cache testable.
*/
interface CacheEntity extends Accountable {
/**
* Called after the value was loaded.
*/
void onCached(Key key, BytesReference value);
/**
* Returns true iff the resource behind this entity is still open ie.
* entities associated with it can remain in the cache. ie. IndexShard is still open.
*/
boolean isOpen();
/**
* Returns the cache identity. this is, similar to {@link #isOpen()} the resource identity behind this cache entity.
* For instance IndexShard is the identity while a CacheEntity is per DirectoryReader. Yet, we group by IndexShard instance.
*/
Object getCacheIdentity();
/**
* Called each time this entity has a cache hit.
*/
void onHit();
/**
* Called each time this entity has a cache miss.
*/
void onMiss();
/**
* Called when this entity instance is removed
*/
void onRemoval(RemovalNotification notification);
}
static class Key implements Accountable {
private static final long BASE_RAM_BYTES_USED = RamUsageEstimator.shallowSizeOfInstance(Key.class);
public final CacheEntity entity; // use as identity equality
public final MappingLookup.CacheKey mappingCacheKey;
public final Object readerCacheKey;
public final BytesReference value;
Key(CacheEntity entity, MappingLookup.CacheKey mappingCacheKey, Object readerCacheKey, BytesReference value) {
this.entity = entity;
this.mappingCacheKey = Objects.requireNonNull(mappingCacheKey);
this.readerCacheKey = Objects.requireNonNull(readerCacheKey);
this.value = value;
}
@Override
public long ramBytesUsed() {
return BASE_RAM_BYTES_USED + entity.ramBytesUsed() + value.length();
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Key key = (Key) o;
if (mappingCacheKey.equals(key.mappingCacheKey) == false) return false;
if (readerCacheKey.equals(key.readerCacheKey) == false) return false;
if (entity.getCacheIdentity().equals(key.entity.getCacheIdentity()) == false) return false;
if (value.equals(key.value) == false) return false;
return true;
}
@Override
public int hashCode() {
int result = entity.getCacheIdentity().hashCode();
result = 31 * result + mappingCacheKey.hashCode();
result = 31 * result + readerCacheKey.hashCode();
result = 31 * result + value.hashCode();
return result;
}
@Override
public String toString() {
return "Key(mappingKey=["
+ mappingCacheKey
+ "],readerKey=["
+ readerCacheKey
+ "],entityKey=["
+ entity.getCacheIdentity()
+ ",value=" // BytesRef's toString already has [] so we don't add it here
+ value.toBytesRef() // BytesRef has a readable toString
+ ")";
}
}
private class CleanupKey implements ESCacheHelper.ClosedListener {
final CacheEntity entity;
final Object readerCacheKey;
private CleanupKey(CacheEntity entity, Object readerCacheKey) {
this.entity = entity;
this.readerCacheKey = readerCacheKey;
}
@Override
public void onClose(Object cacheKey) {
Boolean remove = registeredClosedListeners.remove(this);
if (remove != null) {
keysToClean.add(this);
}
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) {
return false;
}
CleanupKey that = (CleanupKey) o;
if (Objects.equals(readerCacheKey, that.readerCacheKey) == false) return false;
if (entity.getCacheIdentity().equals(that.entity.getCacheIdentity()) == false) return false;
return true;
}
@Override
public int hashCode() {
int result = entity.getCacheIdentity().hashCode();
result = 31 * result + Objects.hashCode(readerCacheKey);
return result;
}
}
synchronized void cleanCache() {
final Set currentKeysToClean = new HashSet<>();
final Set