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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 Backport of elastic#51991
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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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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,67 @@ | ||
| --- | ||
| 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 | ||
| wait_for_events: languid | ||
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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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153
server/src/main/java/org/elasticsearch/index/engine/CompletionStatsCache.java
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| @@ -0,0 +1,153 @@ | ||
| /* | ||
| * 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.Nullable; | ||
| import org.elasticsearch.common.regex.Regex; | ||
| import org.elasticsearch.search.suggest.completion.CompletionStats; | ||
|
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| 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}). | ||
| */ | ||
| @Nullable | ||
| private PlainActionFuture<CompletionStats> completionStatsFuture; | ||
|
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| /** | ||
| * Protects accesses to {@code completionStatsFuture} since we can't use {@link java.util.concurrent.atomic.AtomicReference} in JDK8. | ||
| */ | ||
| private final Object completionStatsFutureMutex = new Object(); | ||
|
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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<>(); | ||
|
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| // final PlainActionFuture<CompletionStats> oldFuture = completionStatsFutureRef.compareAndExchange(null, newFuture); | ||
| // except JDK8 doesn't have compareAndExchange so we emulate it: | ||
| final PlainActionFuture<CompletionStats> oldFuture; | ||
| synchronized (completionStatsFutureMutex) { | ||
| if (completionStatsFuture == null) { | ||
| completionStatsFuture = newFuture; | ||
| oldFuture = null; | ||
| } else { | ||
| oldFuture = completionStatsFuture; | ||
| } | ||
| } | ||
|
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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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| boolean success = false; | ||
| final CompletionStats completionStats; | ||
| try { | ||
| completionStats = newFuture.actionGet(); | ||
| success = true; | ||
| } finally { | ||
| if (success == false) { | ||
| // invalidate the cache (if not already invalidated) so that future calls will retry | ||
|
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| // completionStatsFutureRef.compareAndSet(newFuture, null); except we're not using AtomicReference in JDK8 | ||
| synchronized (completionStatsFutureMutex) { | ||
| if (completionStatsFuture == newFuture) { | ||
| completionStatsFuture = null; | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
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| return filterCompletionStatsByFieldName(fieldNamePatterns, completionStats); | ||
| } | ||
|
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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); except we're not using AtomicReference in JDK8 | ||
| synchronized (completionStatsFutureMutex) { | ||
| completionStatsFuture = null; | ||
| } | ||
| } | ||
| } | ||
| } |
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