Switch to Lucene ProfilerCollector (elastic#95526)

The profile functionality relies on two custom collector implementations
that wrap a given collector to monitor its execution time and expose
the profile results tree. The functionality has been contributed to
Lucene with apache/lucene#144 hence we can start
migrating to relying on the functionalities that Lucene offers for it.

We keep our own collector which extends ProfilerCollector from Lucene
and exposes profile results that extends ProfilerCollectorResult which
can be serialized over the wire as well as to xcontent.

Author: javanna

server/src/main/java/org/elasticsearch/search/profile/query/CollectorResult.java

@@ -8,6 +8,7 @@
 
 package org.elasticsearch.search.profile.query;
 
+import org.apache.lucene.sandbox.search.ProfilerCollectorResult;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
@@ -32,7 +33,7 @@
  * Collectors used in the search.  Children CollectorResult's may be
  * embedded inside of a parent CollectorResult
  */
-public class CollectorResult implements ToXContentObject, Writeable {
+public class CollectorResult extends ProfilerCollectorResult implements ToXContentObject, Writeable {
 
     public static final String REASON_SEARCH_COUNT = "search_count";
     public static final String REASON_SEARCH_TOP_HITS = "search_top_hits";
@@ -49,85 +50,27 @@ public class CollectorResult implements ToXContentObject, Writeable {
     private static final ParseField TIME_NANOS = new ParseField("time_in_nanos");
     private static final ParseField CHILDREN = new ParseField("children");
 
-    /**
-     * A more friendly representation of the Collector's class name
-     */
-    private final String collectorName;
-
-    /**
-     * A "hint" to help provide some context about this Collector
-     */
-    private final String reason;
-
-    /**
-     * The total elapsed time for this Collector
-     */
-    private final long time;
-
-    /**
-     * A list of children collectors "embedded" inside this collector
-     */
-    private final List<CollectorResult> children;
-
     public CollectorResult(String collectorName, String reason, long time, List<CollectorResult> children) {
-        this.collectorName = collectorName;
-        this.reason = reason;
-        this.time = time;
-        this.children = children;
+        super(collectorName, reason, time, new ArrayList<>(children));
     }
 
     /**
      * Read from a stream.
      */
     public CollectorResult(StreamInput in) throws IOException {
-        this.collectorName = in.readString();
-        this.reason = in.readString();
-        this.time = in.readLong();
-        int size = in.readVInt();
-        this.children = new ArrayList<>(size);
-        for (int i = 0; i < size; i++) {
-            CollectorResult child = new CollectorResult(in);
-            this.children.add(child);
-        }
+        super(in.readString(), in.readString(), in.readLong(), in.readList(CollectorResult::new));
     }
 
     @Override
     public void writeTo(StreamOutput out) throws IOException {
-        out.writeString(collectorName);
-        out.writeString(reason);
-        out.writeLong(time);
-        out.writeVInt(children.size());
-        for (CollectorResult child : children) {
-            child.writeTo(out);
-        }
+        out.writeString(getName());
+        out.writeString(getReason());
+        out.writeLong(getTime());
+        out.writeList(getCollectorResults());
     }
 
-    /**
-     * @return the profiled time for this collector (inclusive of children)
-     */
-    public long getTime() {
-        return this.time;
-    }
-
-    /**
-     * @return a human readable "hint" about what this collector was used for
-     */
-    public String getReason() {
-        return this.reason;
-    }
-
-    /**
-     * @return the lucene class name of the collector
-     */
-    public String getName() {
-        return this.collectorName;
-    }
-
-    /**
-     * @return a list of children collectors
-     */
-    public List<CollectorResult> getProfiledChildren() {
-        return children;
+    public List<CollectorResult> getCollectorResults() {
+        return super.getProfiledChildren().stream().map(profilerCollectorResult -> (CollectorResult) profilerCollectorResult).toList();
     }
 
     @Override
@@ -136,15 +79,15 @@ public boolean equals(Object obj) {
             return false;
         }
         CollectorResult other = (CollectorResult) obj;
-        return collectorName.equals(other.collectorName)
-            && reason.equals(other.reason)
-            && time == other.time
-            && children.equals(other.children);
+        return getName().equals(other.getName())
+            && getReason().equals(other.getReason())
+            && getTime() == other.getTime()
+            && getCollectorResults().equals(other.getCollectorResults());
     }
 
     @Override
     public int hashCode() {
-        return Objects.hash(collectorName, reason, time, children);
+        return Objects.hash(getName(), getReason(), getTime(), getCollectorResults());
     }
 
     @Override
@@ -162,9 +105,9 @@ public XContentBuilder toXContent(XContentBuilder builder, ToXContent.Params par
         }
         builder.field(TIME_NANOS.getPreferredName(), getTime());
 
-        if (children.isEmpty() == false) {
+        if (getProfiledChildren().isEmpty() == false) {
             builder = builder.startArray(CHILDREN.getPreferredName());
-            for (CollectorResult child : children) {
+            for (CollectorResult child : getCollectorResults()) {
                 builder = child.toXContent(builder, params);
             }
             builder = builder.endArray();

server/src/main/java/org/elasticsearch/search/profile/query/InternalProfileCollector.java

@@ -8,15 +8,12 @@
 
 package org.elasticsearch.search.profile.query;
 
-import org.apache.lucene.index.LeafReaderContext;
+import org.apache.lucene.sandbox.search.ProfilerCollector;
 import org.apache.lucene.search.Collector;
-import org.apache.lucene.search.LeafCollector;
-import org.apache.lucene.search.ScoreMode;
 
-import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
-import java.util.Objects;
 
 /**
  * This class wraps a Lucene Collector and times the execution of:
@@ -27,56 +24,13 @@
  *
  * InternalProfiler facilitates the linking of the Collector graph
  */
-public class InternalProfileCollector implements Collector {
+public class InternalProfileCollector extends ProfilerCollector {
 
-    /**
-     * A more friendly representation of the Collector's class name
-     */
-    private final String collectorName;
-
-    /**
-     * A "hint" to help provide some context about this Collector
-     */
-    private final String reason;
-
-    /** The wrapped collector */
-    private final ProfileCollector collector;
-
-    /**
-     * An array of "embedded" children collectors
-     */
     private final InternalProfileCollector[] children;
 
-    public InternalProfileCollector(Collector collector, String reason, Collector... children) {
-        this.collector = new ProfileCollector(collector);
-        this.reason = reason;
-        this.collectorName = deriveCollectorName(collector);
-        Objects.requireNonNull(children, "children collectors cannot be null");
-        this.children = new InternalProfileCollector[children.length];
-        for (int i = 0; i < children.length; i++) {
-            this.children[i] = (InternalProfileCollector) Objects.requireNonNull(children[i], "child collector cannot be null");
-        }
-    }
-
-    /**
-     * @return the profiled time for this collector (inclusive of children)
-     */
-    public long getTime() {
-        return collector.getTime();
-    }
-
-    /**
-     * @return a human readable "hint" about what this collector was used for
-     */
-    public String getReason() {
-        return this.reason;
-    }
-
-    /**
-     * @return the lucene class name of the collector
-     */
-    public String getName() {
-        return this.collectorName;
+    public InternalProfileCollector(Collector collector, String reason, InternalProfileCollector... children) {
+        super(collector, reason, Arrays.asList(children));
+        this.children = children;
     }
 
     /**
@@ -88,7 +42,8 @@ public String getName() {
      * @param c The Collector to derive a name from
      * @return  A (hopefully) prettier name
      */
-    private String deriveCollectorName(Collector c) {
+    @Override
+    protected String deriveCollectorName(Collector c) {
         String s = c.getClass().getSimpleName();
 
         // MutiCollector which wraps multiple BucketCollectors is generated
@@ -99,32 +54,18 @@ private String deriveCollectorName(Collector c) {
         }
 
         // Aggregation collector toString()'s include the user-defined agg name
-        if (reason.equals(CollectorResult.REASON_AGGREGATION) || reason.equals(CollectorResult.REASON_AGGREGATION_GLOBAL)) {
-            s += ": [" + c.toString() + "]";
+        if (getReason().equals(CollectorResult.REASON_AGGREGATION) || getReason().equals(CollectorResult.REASON_AGGREGATION_GLOBAL)) {
+            s += ": [" + c + "]";
         }
         return s;
     }
 
-    @Override
-    public LeafCollector getLeafCollector(LeafReaderContext context) throws IOException {
-        return collector.getLeafCollector(context);
-    }
-
-    @Override
-    public ScoreMode scoreMode() {
-        return collector.scoreMode();
-    }
-
     public CollectorResult getCollectorTree() {
-        return InternalProfileCollector.doGetCollectorTree(this);
-    }
-
-    private static CollectorResult doGetCollectorTree(InternalProfileCollector collector) {
-        List<CollectorResult> childResults = new ArrayList<>(collector.children.length);
-        for (InternalProfileCollector child : collector.children) {
-            CollectorResult result = doGetCollectorTree(child);
+        List<CollectorResult> childResults = new ArrayList<>(children.length);
+        for (InternalProfileCollector child : children) {
+            CollectorResult result = child.getCollectorTree();
             childResults.add(result);
         }
-        return new CollectorResult(collector.getName(), collector.getReason(), collector.getTime(), childResults);
+        return new CollectorResult(getName(), getReason(), getTime(), childResults);
     }
 }

server/src/main/java/org/elasticsearch/search/profile/query/ProfileCollector.java

@@ -52,6 +52,7 @@
 
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 import java.util.concurrent.ExecutorService;
 
@@ -309,7 +310,10 @@ private static CollectorManager<Collector, Void> wrapWithProfilerCollectorManage
         if (profilers == null) {
             return new SingleThreadCollectorManager(collector);
         }
-        return new InternalProfileCollectorManager(new InternalProfileCollector(collector, profilerName, children));
+        InternalProfileCollector[] childProfileCollectors = Arrays.stream(children)
+            .map(c -> (InternalProfileCollector) c)
+            .toArray(InternalProfileCollector[]::new);
+        return new InternalProfileCollectorManager(new InternalProfileCollector(collector, profilerName, childProfileCollectors));
     }
 
     private static void searchWithCollectorManager(