use Randomness.get()

Author: jan-elastic

test/framework/src/main/java/org/elasticsearch/test/MixWithIncrement.java

@@ -0,0 +1,73 @@
+/*
+ * 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", the "GNU Affero General Public License v3.0 only", 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", the "GNU Affero General Public
+ * License v3.0 only", or the "Server Side Public License, v 1".
+ */
+
+package org.elasticsearch.test;
+
+import com.carrotsearch.randomizedtesting.SeedDecorator;
+
+import org.elasticsearch.common.Randomness;
+
+import java.util.concurrent.atomic.AtomicLong;
+
+/**
+ * The {@link Randomness} class creates random generators with the same seed
+ * in every thread.
+ * <p>
+ * This means that repeatedly calling:
+ * <pre>
+ *   {@code
+ *     new Thread(() -> System.out.println(Randomness.get().nextInt())).start();
+ *   }
+ * </pre>
+ * will print the same number in every thread.
+ * <p>
+ * For some use cases, this is not desirable, e.g. when testing that the random
+ * behavior obeys certain statistical properties.
+ * <p>
+ * To fix this, annotate a test class with:
+ * <pre>
+ *   {@code
+ *     @SeedDecorators(MixWithIncrement.class)
+ *   }
+ * </pre>
+ * In this way, an additional seed is mixed into the seed of the random generators.
+ * This additional seed can be updated be calling:
+ * <pre>
+ *   {@code
+ *     MixWithIncrement.next()
+ *   }
+ * </pre>
+ * to make sure that new threads will get a different seed.
+ */
+public class MixWithIncrement implements SeedDecorator {
+
+    private static final AtomicLong mix = new AtomicLong(1);
+
+    @Override
+    public void initialize(Class<?> aClass) {
+        next();
+    }
+
+    public long decorate(long seed) {
+        return seed ^ mix.get();
+    }
+
+    public static void next() {
+        mix.updateAndGet(MixWithIncrement::fmix64);
+    }
+
+    private static long fmix64(long k) {
+        k ^= k >>> 33;
+        k *= -49064778989728563L;
+        k ^= k >>> 33;
+        k *= -4265267296055464877L;
+        k ^= k >>> 33;
+        return k;
+    }
+}

x-pack/plugin/esql/compute/src/main/generated-src/org/elasticsearch/compute/aggregation/SampleBooleanAggregator.java

@@ -26,7 +26,7 @@ import org.elasticsearch.compute.operator.topn.DefaultUnsortableTopNEncoder;
 import org.elasticsearch.core.Releasables;
 import org.elasticsearch.search.sort.SortOrder;
 
-import java.util.SplittableRandom;
+import org.elasticsearch.common.Randomness;
 import java.util.random.RandomGenerator;
 // end generated imports
 
@@ -125,20 +125,17 @@ class Sample$Type$Aggregator {
     }
 
     public static class GroupingState implements GroupingAggregatorState {
-        private final CircuitBreaker breaker;
         private final BytesRefBucketedSort sort;
         private final BreakingBytesRefBuilder bytesRefBuilder;
-        private final RandomGenerator random;
 
         private GroupingState(BigArrays bigArrays, int limit) {
-            this.breaker = bigArrays.breakerService().getBreaker(CircuitBreaker.REQUEST);
+            CircuitBreaker breaker = bigArrays.breakerService().getBreaker(CircuitBreaker.REQUEST);
             this.sort = new BytesRefBucketedSort(breaker, "sample", bigArrays, SortOrder.ASC, limit);
             this.bytesRefBuilder = new BreakingBytesRefBuilder(breaker, "sample");
-            this.random = new SplittableRandom();
         }
 
         public void add(int groupId, $type$ value) {
-            ENCODER.encodeLong(random.nextLong(), bytesRefBuilder);
+            ENCODER.encodeLong(Randomness.get().nextLong(), bytesRefBuilder);
             ENCODER.encode$Type$(value, bytesRefBuilder);
             sort.collect(bytesRefBuilder.bytesRefView(), groupId);
             bytesRefBuilder.clear();

x-pack/plugin/esql/compute/src/main/generated-src/org/elasticsearch/compute/aggregation/SampleBytesRefAggregator.java

@@ -7,6 +7,8 @@
 
 package org.elasticsearch.compute.aggregation;
 
+import com.carrotsearch.randomizedtesting.annotations.SeedDecorators;
+
 import org.elasticsearch.compute.data.Block;
 import org.elasticsearch.compute.data.BlockFactory;
 import org.elasticsearch.compute.data.BooleanBlock;
@@ -15,6 +17,7 @@
 import org.elasticsearch.compute.operator.SequenceBooleanBlockSourceOperator;
 import org.elasticsearch.compute.operator.SourceOperator;
 import org.elasticsearch.compute.test.CannedSourceOperator;
+import org.elasticsearch.test.MixWithIncrement;
 
 import java.util.List;
 import java.util.stream.Collectors;
@@ -25,6 +28,7 @@
 import static org.hamcrest.Matchers.greaterThan;
 import static org.hamcrest.Matchers.lessThan;
 
+@SeedDecorators(MixWithIncrement.class)
 public class SampleBooleanAggregatorFunctionTests extends AggregatorFunctionTestCase {
     private static final int LIMIT = 50;
 
@@ -77,6 +81,7 @@ public void testDistribution() {
                     }
                 }
             }
+            MixWithIncrement.next();
         }
 
         // On average, both boolean values should be sampled 25000x.

x-pack/plugin/esql/compute/src/main/generated-src/org/elasticsearch/compute/aggregation/SampleDoubleAggregator.java

@@ -7,6 +7,8 @@
 
 package org.elasticsearch.compute.aggregation;
 
+import com.carrotsearch.randomizedtesting.annotations.SeedDecorators;
+
 import org.apache.lucene.util.BytesRef;
 import org.elasticsearch.compute.data.Block;
 import org.elasticsearch.compute.data.BlockFactory;
@@ -16,6 +18,7 @@
 import org.elasticsearch.compute.operator.SequenceBytesRefBlockSourceOperator;
 import org.elasticsearch.compute.operator.SourceOperator;
 import org.elasticsearch.compute.test.CannedSourceOperator;
+import org.elasticsearch.test.MixWithIncrement;
 
 import java.util.List;
 import java.util.Set;
@@ -28,6 +31,7 @@
 import static org.hamcrest.Matchers.hasItems;
 import static org.hamcrest.Matchers.lessThan;
 
+@SeedDecorators(MixWithIncrement.class)
 public class SampleBytesRefAggregatorFunctionTests extends AggregatorFunctionTestCase {
     private static final int LIMIT = 50;
 
@@ -83,6 +87,7 @@ public void testDistribution() {
                     sampledCounts[Integer.parseInt(block.getBytesRef(i, scratch).utf8ToString())]++;
                 }
             }
+            MixWithIncrement.next();
         }
 
         // On average, each string should be sampled 500x.

x-pack/plugin/esql/compute/src/main/generated-src/org/elasticsearch/compute/aggregation/SampleIntAggregator.java

@@ -7,6 +7,8 @@
 
 package org.elasticsearch.compute.aggregation;
 
+import com.carrotsearch.randomizedtesting.annotations.SeedDecorators;
+
 import org.elasticsearch.compute.data.Block;
 import org.elasticsearch.compute.data.BlockFactory;
 import org.elasticsearch.compute.data.DoubleBlock;
@@ -15,6 +17,7 @@
 import org.elasticsearch.compute.operator.SequenceDoubleBlockSourceOperator;
 import org.elasticsearch.compute.operator.SourceOperator;
 import org.elasticsearch.compute.test.CannedSourceOperator;
+import org.elasticsearch.test.MixWithIncrement;
 
 import java.util.List;
 import java.util.Set;
@@ -27,6 +30,7 @@
 import static org.hamcrest.Matchers.hasItems;
 import static org.hamcrest.Matchers.lessThan;
 
+@SeedDecorators(MixWithIncrement.class)
 public class SampleDoubleAggregatorFunctionTests extends AggregatorFunctionTestCase {
     private static final int LIMIT = 50;
 
@@ -78,6 +82,7 @@ public void testDistribution() {
                     sampledCounts[(int) block.getDouble(i)]++;
                 }
             }
+            MixWithIncrement.next();
         }
 
         // On average, each number should be sampled 500x.