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Cache completion stats between refreshes
Computing the stats for completion fields may involve a significant amount of work since it walks every field of every segment looking for completion fields. Innocuous-looking APIs like `GET _stats` or `GET _cluster/stats` do this for every shard in the cluster. This repeated work is unnecessary since these stats do not change between refreshes; in many indices they remain constant for a long time. This commit introduces a cache for these stats which is invalidated on a refresh, allowing most stats calls to bypass the work needed to compute them on most shards. Closes elastic#51915
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rest-api-spec/src/main/resources/rest-api-spec/test/indices.stats/40_updates_on_refresh.yml
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--- | ||
setup: | ||
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- do: | ||
indices.create: | ||
index: test1 | ||
wait_for_active_shards: all | ||
body: | ||
settings: | ||
# Limit the number of shards so that shards are unlikely | ||
# to be relocated or being initialized between the test | ||
# set up and the test execution | ||
index.number_of_shards: 3 | ||
index.number_of_replicas: 0 | ||
mappings: | ||
properties: | ||
bar: | ||
type: text | ||
fielddata: true | ||
fields: | ||
completion: | ||
type: completion | ||
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- do: | ||
cluster.health: | ||
wait_for_no_relocating_shards: true | ||
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- do: | ||
index: | ||
index: test1 | ||
id: 1 | ||
body: { "bar": "bar" } | ||
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- do: | ||
index: | ||
index: test1 | ||
id: 2 | ||
body: { "bar": "foo" } | ||
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- do: | ||
indices.refresh: {} | ||
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--- | ||
"Completion stats": | ||
- do: | ||
indices.stats: { completion_fields: "*" } | ||
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- match: { _shards.failed: 0} | ||
- gt: { _all.total.completion.fields.bar\.completion.size_in_bytes: 0 } | ||
- gt: { _all.total.completion.size_in_bytes: 0 } | ||
- set: { _all.total.completion.size_in_bytes: original_size } | ||
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- do: | ||
index: | ||
index: test1 | ||
id: 3 | ||
body: { "bar": "foo", "baz": "foo" } | ||
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- do: | ||
indices.refresh: {} | ||
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- do: | ||
indices.stats: { completion_fields: "*" } | ||
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- match: { _shards.failed: 0} | ||
- gt: { _all.total.completion.size_in_bytes: $original_size } |
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server/src/main/java/org/elasticsearch/index/engine/CompletionStatsCache.java
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/* | ||
* Licensed to Elasticsearch under one or more contributor | ||
* license agreements. See the NOTICE file distributed with | ||
* this work for additional information regarding copyright | ||
* ownership. Elasticsearch 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.elasticsearch.index.engine; | ||
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import com.carrotsearch.hppc.ObjectLongHashMap; | ||
import com.carrotsearch.hppc.cursors.ObjectLongCursor; | ||
import org.apache.lucene.index.FieldInfo; | ||
import org.apache.lucene.index.LeafReader; | ||
import org.apache.lucene.index.LeafReaderContext; | ||
import org.apache.lucene.index.Terms; | ||
import org.apache.lucene.search.ReferenceManager; | ||
import org.apache.lucene.search.suggest.document.CompletionTerms; | ||
import org.elasticsearch.action.ActionListener; | ||
import org.elasticsearch.action.support.PlainActionFuture; | ||
import org.elasticsearch.common.FieldMemoryStats; | ||
import org.elasticsearch.common.regex.Regex; | ||
import org.elasticsearch.search.suggest.completion.CompletionStats; | ||
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import java.util.concurrent.atomic.AtomicReference; | ||
import java.util.function.Supplier; | ||
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class CompletionStatsCache implements ReferenceManager.RefreshListener { | ||
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private final Supplier<Engine.Searcher> searcherSupplier; | ||
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/** | ||
* Contains a future (i.e. non-null) if another thread is already computing stats, in which case wait for this computation to | ||
* complete. Contains null otherwise, in which case compute the stats ourselves and save them here for other threads to use. | ||
* Futures are eventually completed with stats that include all fields, requiring further filtering (see | ||
* {@link CompletionStatsCache#filterCompletionStatsByFieldName}). | ||
*/ | ||
private final AtomicReference<PlainActionFuture<CompletionStats>> completionStatsFutureRef = new AtomicReference<>(); | ||
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CompletionStatsCache(Supplier<Engine.Searcher> searcherSupplier) { | ||
this.searcherSupplier = searcherSupplier; | ||
} | ||
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CompletionStats get(String... fieldNamePatterns) { | ||
final PlainActionFuture<CompletionStats> newFuture = new PlainActionFuture<>(); | ||
final PlainActionFuture<CompletionStats> oldFuture = completionStatsFutureRef.compareAndExchange(null, newFuture); | ||
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if (oldFuture != null) { | ||
// we lost the race, someone else is already computing stats, so we wait for that to finish | ||
return filterCompletionStatsByFieldName(fieldNamePatterns, oldFuture.actionGet()); | ||
} | ||
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// we won the race, nobody else is already computing stats, so it's up to us | ||
ActionListener.completeWith(newFuture, () -> { | ||
long sizeInBytes = 0; | ||
final ObjectLongHashMap<String> completionFields = new ObjectLongHashMap<>(); | ||
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try (Engine.Searcher currentSearcher = searcherSupplier.get()) { | ||
for (LeafReaderContext atomicReaderContext : currentSearcher.getIndexReader().leaves()) { | ||
LeafReader atomicReader = atomicReaderContext.reader(); | ||
for (FieldInfo info : atomicReader.getFieldInfos()) { | ||
Terms terms = atomicReader.terms(info.name); | ||
if (terms instanceof CompletionTerms) { | ||
// TODO: currently we load up the suggester for reporting its size | ||
final long fstSize = ((CompletionTerms) terms).suggester().ramBytesUsed(); | ||
completionFields.addTo(info.name, fstSize); | ||
sizeInBytes += fstSize; | ||
} | ||
} | ||
} | ||
} | ||
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return new CompletionStats(sizeInBytes, new FieldMemoryStats(completionFields)); | ||
}); | ||
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return filterCompletionStatsByFieldName(fieldNamePatterns, newFuture.actionGet()); | ||
} | ||
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private static CompletionStats filterCompletionStatsByFieldName(String[] fieldNamePatterns, CompletionStats fullCompletionStats) { | ||
final FieldMemoryStats fieldMemoryStats; | ||
if (fieldNamePatterns != null && fieldNamePatterns.length > 0) { | ||
final ObjectLongHashMap<String> completionFields = new ObjectLongHashMap<>(fieldNamePatterns.length); | ||
for (ObjectLongCursor<String> fieldCursor : fullCompletionStats.getFields()) { | ||
if (Regex.simpleMatch(fieldNamePatterns, fieldCursor.key)) { | ||
completionFields.addTo(fieldCursor.key, fieldCursor.value); | ||
} | ||
} | ||
fieldMemoryStats = new FieldMemoryStats(completionFields); | ||
} else { | ||
fieldMemoryStats = null; | ||
} | ||
return new CompletionStats(fullCompletionStats.getSizeInBytes(), fieldMemoryStats); | ||
} | ||
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@Override | ||
public void beforeRefresh() { | ||
} | ||
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@Override | ||
public void afterRefresh(boolean didRefresh) { | ||
if (didRefresh) { | ||
completionStatsFutureRef.set(null); | ||
} | ||
} | ||
} |
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