[Backport 2.x] Perform buildAggregation concurrently and partially support composite aggs

CHANGELOG.md

@@ -6,6 +6,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 ## [Unreleased 2.x]
 ### Added
 - Add explicit dependency to validatePom and generatePom tasks ([#12909](https://github.com/opensearch-project/OpenSearch/pull/12909))
+- [Concurrent Segment Search] Perform buildAggregation concurrently and support Composite Aggregations ([#12697](https://github.com/opensearch-project/OpenSearch/pull/12697))
 
 ### Dependencies
 - Bump `org.apache.commons:commons-configuration2` from 2.10.0 to 2.10.1 ([#12896](https://github.com/opensearch-project/OpenSearch/pull/12896))

server/src/internalClusterTest/java/org/opensearch/search/aggregations/AggregationsIntegrationIT.java

@@ -38,6 +38,8 @@
 import org.opensearch.action.index.IndexRequestBuilder;
 import org.opensearch.action.search.SearchPhaseExecutionException;
 import org.opensearch.action.search.SearchResponse;
+import org.opensearch.action.support.WriteRequest;
+import org.opensearch.cluster.metadata.IndexMetadata;
 import org.opensearch.common.settings.Settings;
 import org.opensearch.common.unit.TimeValue;
 import org.opensearch.search.aggregations.bucket.terms.IncludeExclude;
@@ -56,6 +58,8 @@
 import java.util.List;
 
 import static org.opensearch.search.SearchService.CLUSTER_CONCURRENT_SEGMENT_SEARCH_SETTING;
+import static org.opensearch.search.aggregations.AggregationBuilders.global;
+import static org.opensearch.search.aggregations.AggregationBuilders.stats;
 import static org.opensearch.search.aggregations.AggregationBuilders.terms;
 import static org.opensearch.test.hamcrest.OpenSearchAssertions.assertAcked;
 import static org.opensearch.test.hamcrest.OpenSearchAssertions.assertSearchResponse;
@@ -164,4 +168,23 @@ private void runLargeStringAggregationTest(AggregationBuilder aggregation) {
         }
         assertTrue("Exception should have been thrown", exceptionThrown);
     }
+
+    public void testAggsOnEmptyShards() {
+        // Create index with 5 shards but only 1 doc
+        assertAcked(
+            prepareCreate(
+                "idx",
+                Settings.builder().put(IndexMetadata.SETTING_NUMBER_OF_SHARDS, 5).put(IndexMetadata.SETTING_NUMBER_OF_REPLICAS, 0)
+            ).setMapping("score", "type=integer")
+        );
+        client().prepareIndex("idx").setId("1").setSource("score", "5").setRefreshPolicy(WriteRequest.RefreshPolicy.IMMEDIATE).get();
+
+        // Validate global agg does not throw an exception
+        assertSearchResponse(
+            client().prepareSearch("idx").addAggregation(global("global").subAggregation(stats("value_stats").field("score"))).get()
+        );
+
+        // Validate non-global agg does not throw an exception
+        assertSearchResponse(client().prepareSearch("idx").addAggregation(stats("value_stats").field("score")).get());
+    }
 }

server/src/internalClusterTest/java/org/opensearch/search/aggregations/bucket/CompositeAggIT.java

@@ -26,6 +26,7 @@
 import java.util.Collection;
 import java.util.List;
 
+import static org.opensearch.indices.IndicesRequestCache.INDEX_CACHE_REQUEST_ENABLED_SETTING;
 import static org.opensearch.search.SearchService.CLUSTER_CONCURRENT_SEGMENT_SEARCH_SETTING;
 import static org.opensearch.test.hamcrest.OpenSearchAssertions.assertAcked;
 import static org.opensearch.test.hamcrest.OpenSearchAssertions.assertSearchResponse;
@@ -50,23 +51,25 @@ public void setupSuiteScopeCluster() throws Exception {
         assertAcked(
             prepareCreate(
                 "idx",
-                Settings.builder().put(IndexMetadata.SETTING_NUMBER_OF_SHARDS, 1).put(IndexMetadata.SETTING_NUMBER_OF_REPLICAS, 0)
+                Settings.builder()
+                    .put(IndexMetadata.SETTING_NUMBER_OF_SHARDS, 1)
+                    .put(IndexMetadata.SETTING_NUMBER_OF_REPLICAS, 0)
+                    .put(INDEX_CACHE_REQUEST_ENABLED_SETTING.getKey(), false)
             ).setMapping("type", "type=keyword", "num", "type=integer", "score", "type=integer")
         );
         waitForRelocation(ClusterHealthStatus.GREEN);
 
-        client().prepareIndex("idx").setId("1").setSource("type", "type1", "num", "1", "score", "5").get();
-        client().prepareIndex("idx").setId("1").setSource("type", "type2", "num", "11", "score", "50").get();
-        refresh("idx");
-        client().prepareIndex("idx").setId("1").setSource("type", "type1", "num", "1", "score", "2").get();
-        client().prepareIndex("idx").setId("1").setSource("type", "type2", "num", "12", "score", "20").get();
-        refresh("idx");
-        client().prepareIndex("idx").setId("1").setSource("type", "type1", "num", "3", "score", "10").get();
-        client().prepareIndex("idx").setId("1").setSource("type", "type2", "num", "13", "score", "15").get();
-        refresh("idx");
-        client().prepareIndex("idx").setId("1").setSource("type", "type1", "num", "3", "score", "1").get();
-        client().prepareIndex("idx").setId("1").setSource("type", "type2", "num", "13", "score", "100").get();
-        refresh("idx");
+        indexRandom(
+            true,
+            client().prepareIndex("idx").setId("1").setSource("type", "type1", "num", "1", "score", "5"),
+            client().prepareIndex("idx").setId("1").setSource("type", "type2", "num", "11", "score", "50"),
+            client().prepareIndex("idx").setId("1").setSource("type", "type1", "num", "1", "score", "2"),
+            client().prepareIndex("idx").setId("1").setSource("type", "type2", "num", "12", "score", "20"),
+            client().prepareIndex("idx").setId("1").setSource("type", "type1", "num", "3", "score", "10"),
+            client().prepareIndex("idx").setId("1").setSource("type", "type2", "num", "13", "score", "15"),
+            client().prepareIndex("idx").setId("1").setSource("type", "type1", "num", "3", "score", "1"),
+            client().prepareIndex("idx").setId("1").setSource("type", "type2", "num", "13", "score", "100")
+        );
 
         waitForRelocation(ClusterHealthStatus.GREEN);
         refresh();

server/src/main/java/org/opensearch/search/aggregations/AggregationCollectorManager.java

@@ -15,9 +15,9 @@
 import org.opensearch.search.query.ReduceableSearchResult;
 
 import java.io.IOException;
-import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
+import java.util.Objects;
 
 /**
  * Common {@link CollectorManager} used by both concurrent and non-concurrent aggregation path and also for global and non-global
@@ -56,17 +56,9 @@ public String getCollectorReason() {
 
     @Override
     public ReduceableSearchResult reduce(Collection<Collector> collectors) throws IOException {
-        final List<Aggregator> aggregators = context.bucketCollectorProcessor().toAggregators(collectors);
-        final List<InternalAggregation> internals = new ArrayList<>(aggregators.size());
+        final List<InternalAggregation> internals = context.bucketCollectorProcessor().toInternalAggregations(collectors);
+        assert internals.stream().noneMatch(Objects::isNull);
         context.aggregations().resetBucketMultiConsumer();
-        for (Aggregator aggregator : aggregators) {
-            try {
-                // post collection is called in ContextIndexSearcher after search on leaves are completed
-                internals.add(aggregator.buildTopLevel());
-            } catch (IOException e) {
-                throw new AggregationExecutionException("Failed to build aggregation [" + aggregator.name() + "]", e);
-            }
-        }
 
         // PipelineTreeSource is serialized to the coordinators on older OpenSearch versions for bwc but is deprecated in latest release
         // To handle that we need to add it in the InternalAggregations object sent in QuerySearchResult.

server/src/main/java/org/opensearch/search/aggregations/Aggregator.java

@@ -33,6 +33,7 @@
 package org.opensearch.search.aggregations;
 
 import org.opensearch.OpenSearchParseException;
+import org.opensearch.common.SetOnce;
 import org.opensearch.common.annotation.PublicApi;
 import org.opensearch.common.lease.Releasable;
 import org.opensearch.core.ParseField;
@@ -61,6 +62,8 @@
 @PublicApi(since = "1.0.0")
 public abstract class Aggregator extends BucketCollector implements Releasable {
 
+    private final SetOnce<InternalAggregation> internalAggregation = new SetOnce<>();
+
     /**
      * Parses the aggregation request and creates the appropriate aggregator factory for it.
      *
@@ -83,6 +86,13 @@ public interface Parser {
         AggregationBuilder parse(String aggregationName, XContentParser parser) throws IOException;
     }
 
+    /**
+     * Returns the InternalAggregation stored during post collection
+     */
+    public InternalAggregation getPostCollectionAggregation() {
+        return internalAggregation.get();
+    }
+
     /**
      * Return the name of this aggregator.
      */
@@ -185,13 +195,15 @@ public interface BucketComparator {
 
     /**
      * Build the result of this aggregation if it is at the "top level"
-     * of the aggregation tree. If, instead, it is a sub-aggregation of
-     * another aggregation then the aggregation that contains it will call
-     * {@link #buildAggregations(long[])}.
+     * of the aggregation tree and save it. This should get called
+     * during post collection. If, instead, it is a sub-aggregation
+     * of another aggregation then the aggregation that contains
+     * it will call {@link #buildAggregations(long[])}.
      */
     public final InternalAggregation buildTopLevel() throws IOException {
         assert parent() == null;
-        return buildAggregations(new long[] { 0 })[0];
+        this.internalAggregation.set(buildAggregations(new long[] { 0 })[0]);
+        return internalAggregation.get();
     }
 
     /**

server/src/main/java/org/opensearch/search/aggregations/BucketCollectorProcessor.java

@@ -72,6 +72,15 @@
                 }
             } else if (currentCollector instanceof BucketCollector) {
                 ((BucketCollector) currentCollector).postCollection();
+
+                // Perform build aggregation during post collection
+                if (currentCollector instanceof Aggregator) {
+                    ((Aggregator) currentCollector).buildTopLevel();
+                } else if (currentCollector instanceof MultiBucketCollector) {
+                    for (Collector innerCollector : ((MultiBucketCollector) currentCollector).getCollectors()) {
+                        collectors.offer(innerCollector);
+                    }
+                }
             }
         }
     }
@@ -106,4 +115,31 @@
         }
         return aggregators;
     }
+
+    /**
+     * Unwraps the input collection of {@link Collector} to get the list of the {@link InternalAggregation}. The
+     * input is expected to contain the collectors related to Aggregations only as that is passed to {@link AggregationCollectorManager}
+     * during the reduce phase. This list of {@link InternalAggregation} is used to optionally perform reduce at shard level before
+     * returning response to coordinator
+     * @param collectors collection of aggregation collectors to reduce
+     * @return list of unwrapped {@link InternalAggregation}
+     */
+    public List<InternalAggregation> toInternalAggregations(Collection<Collector> collectors) throws IOException {
+        List<InternalAggregation> internalAggregations = new ArrayList<>();
+
+        final Deque<Collector> allCollectors = new LinkedList<>(collectors);
+        while (!allCollectors.isEmpty()) {
+            Collector currentCollector = allCollectors.pop();
+            if (currentCollector instanceof InternalProfileCollector) {
+                currentCollector = ((InternalProfileCollector) currentCollector).getCollector();
+            }
+
+            if (currentCollector instanceof Aggregator) {
+                internalAggregations.add(((Aggregator) currentCollector).getPostCollectionAggregation());
+            } else if (currentCollector instanceof MultiBucketCollector) {
+                allCollectors.addAll(Arrays.asList(((MultiBucketCollector) currentCollector).getCollectors()));
+            }
+        }
+        return internalAggregations;
+    }
 }

server/src/main/java/org/opensearch/search/aggregations/GlobalAggCollectorManager.java

@@ -12,8 +12,10 @@
 import org.apache.lucene.search.CollectorManager;
 import org.opensearch.search.internal.SearchContext;
 import org.opensearch.search.profile.query.CollectorResult;
+import org.opensearch.search.query.ReduceableSearchResult;
 
 import java.io.IOException;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.Objects;
 
@@ -42,6 +44,19 @@
         }
     }
 
+    @Override
+    public ReduceableSearchResult reduce(Collection<Collector> collectors) throws IOException {
+        // If there are no leaves then in concurrent search case postCollection, and subsequently buildAggregation, will not be called in
+        // search path. Since we build the InternalAggregation in postCollection that will not get created in such cases either. Therefore
+        // we need to manually processPostCollection here to build empty InternalAggregation objects for this collector tree.
+        if (context.searcher().getLeafContexts().isEmpty()) {
+            for (Collector c : collectors) {
+                context.bucketCollectorProcessor().processPostCollection(c);
+            }
+        }
+        return super.reduce(collectors);
+    }
+
     @Override
     protected AggregationReduceableSearchResult buildAggregationResult(InternalAggregations internalAggregations) {
         // Reduce the aggregations across slices before sending to the coordinator. We will perform shard level reduce as long as any slices

server/src/main/java/org/opensearch/search/aggregations/MultiBucketConsumerService.java

@@ -131,12 +131,10 @@ public static class MultiBucketConsumer implements IntConsumer {
         private final int limit;
         private final CircuitBreaker breaker;
 
-        // aggregations execute in a single thread for both sequential
-        // and concurrent search, so no atomic here
+        // count is currently only updated in final reduce phase which is executed in single thread for both concurrent and non-concurrent
+        // search
         private int count;
-
-        // will be updated by multiple threads in concurrent search
-        // hence making it as LongAdder
+        // will be updated by multiple threads in concurrent search hence making it as LongAdder
         private final LongAdder callCount;
         private volatile boolean circuitBreakerTripped;
         private final int availProcessors;

server/src/main/java/org/opensearch/search/aggregations/NonGlobalAggCollectorManager.java

@@ -12,8 +12,10 @@
 import org.apache.lucene.search.CollectorManager;
 import org.opensearch.search.internal.SearchContext;
 import org.opensearch.search.profile.query.CollectorResult;
+import org.opensearch.search.query.ReduceableSearchResult;
 
 import java.io.IOException;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.Objects;
 
@@ -42,6 +44,19 @@
         }
     }
 
+    @Override
+    public ReduceableSearchResult reduce(Collection<Collector> collectors) throws IOException {
+        // If there are no leaves then in concurrent search case postCollection, and subsequently buildAggregation, will not be called in
+        // search path. Since we build the InternalAggregation in postCollection that will not get created in such cases either. Therefore
+        // we need to manually processPostCollection here to build empty InternalAggregation objects for this collector tree.
+        if (context.searcher().getLeafContexts().isEmpty()) {
+            for (Collector c : collectors) {
+                context.bucketCollectorProcessor().processPostCollection(c);
+            }
+        }
+        return super.reduce(collectors);
+    }
+
     @Override
     protected AggregationReduceableSearchResult buildAggregationResult(InternalAggregations internalAggregations) {
         // Reduce the aggregations across slices before sending to the coordinator. We will perform shard level reduce as long as any slices

server/src/main/java/org/opensearch/search/aggregations/bucket/composite/CompositeAggregationFactory.java

@@ -40,6 +40,7 @@
 import org.opensearch.search.internal.SearchContext;
 
 import java.io.IOException;
+import java.util.Arrays;
 import java.util.Map;
 
 /**
@@ -80,7 +81,7 @@
 
     @Override
     protected boolean supportsConcurrentSegmentSearch() {
-        // See https://github.com/opensearch-project/OpenSearch/issues/12331 for details
-        return false;
+        // Disable concurrent search if any scripting is used. See https://github.com/opensearch-project/OpenSearch/issues/12331 for details
+        return Arrays.stream(sources).noneMatch(CompositeValuesSourceConfig::hasScript);
     }
 }

server/src/main/java/org/opensearch/search/aggregations/bucket/terms/GlobalOrdinalsStringTermsAggregator.java

@@ -45,6 +45,7 @@
 import org.apache.lucene.util.ArrayUtil;
 import org.apache.lucene.util.BytesRef;
 import org.apache.lucene.util.PriorityQueue;
+import org.opensearch.common.SetOnce;
 import org.opensearch.common.lease.Releasable;
 import org.opensearch.common.lease.Releasables;
 import org.opensearch.common.util.LongArray;
@@ -94,8 +95,8 @@
     private final long valueCount;
     private final String fieldName;
     private Weight weight;
-    private final GlobalOrdLookupFunction lookupGlobalOrd;
     protected final CollectionStrategy collectionStrategy;
+    private final SetOnce<SortedSetDocValues> dvs = new SetOnce<>();
     protected int segmentsWithSingleValuedOrds = 0;
     protected int segmentsWithMultiValuedOrds = 0;
 
@@ -129,11 +130,10 @@
         this.resultStrategy = resultStrategy.apply(this); // ResultStrategy needs a reference to the Aggregator to do its job.
         this.valuesSource = valuesSource;
         final IndexReader reader = context.searcher().getIndexReader();
-        final SortedSetDocValues values = reader.leaves().size() > 0
+        final SortedSetDocValues values = !reader.leaves().isEmpty()
             ? valuesSource.globalOrdinalsValues(context.searcher().getIndexReader().leaves().get(0))
             : DocValues.emptySortedSet();
         this.valueCount = values.getValueCount();
-        this.lookupGlobalOrd = values::lookupOrd;
         this.acceptedGlobalOrdinals = includeExclude == null ? ALWAYS_TRUE : includeExclude.acceptedGlobalOrdinals(values)::get;
         if (remapGlobalOrds) {
             this.collectionStrategy = new RemapGlobalOrds(cardinality);
@@ -885,7 +885,10 @@
         }
 
         StringTerms.Bucket convertTempBucketToRealBucket(OrdBucket temp) throws IOException {
-            BytesRef term = BytesRef.deepCopyOf(lookupGlobalOrd.apply(temp.globalOrd));
+            // Recreate DocValues as needed for concurrent segment search
+            SortedSetDocValues values = getDocValues();
+            BytesRef term = BytesRef.deepCopyOf(values.lookupOrd(temp.globalOrd));
+
             StringTerms.Bucket result = new StringTerms.Bucket(term, temp.docCount, null, showTermDocCountError, 0, format);
             result.bucketOrd = temp.bucketOrd;
             result.docCountError = 0;
@@ -1001,7 +1004,9 @@
             long subsetSize = subsetSize(owningBucketOrd);
             return (spare, globalOrd, bucketOrd, docCount) -> {
                 spare.bucketOrd = bucketOrd;
-                oversizedCopy(lookupGlobalOrd.apply(globalOrd), spare.termBytes);
+                // Recreate DocValues as needed for concurrent segment search
+                SortedSetDocValues values = getDocValues();
+                oversizedCopy(values.lookupOrd(globalOrd), spare.termBytes);
                 spare.subsetDf = docCount;
                 spare.subsetSize = subsetSize;
                 spare.supersetDf = backgroundFrequencies.freq(spare.termBytes);
@@ -1086,4 +1091,18 @@
      * Predicate used for {@link #acceptedGlobalOrdinals} if there is no filter.
      */
     private static final LongPredicate ALWAYS_TRUE = l -> true;
+
+    /**
+     * If DocValues have not been initialized yet for reduce phase, create and set them.
+     */
+    private SortedSetDocValues getDocValues() throws IOException {
+        if (dvs.get() == null) {
+            dvs.set(
+                !context.searcher().getIndexReader().leaves().isEmpty()
+                    ? valuesSource.globalOrdinalsValues(context.searcher().getIndexReader().leaves().get(0))
+                    : DocValues.emptySortedSet()
+            );
+        }
+        return dvs.get();
+    }
 }