Re: [PR] Implement LockFreeHistogram and use it for PerWorkerHistograms [beam]

["m-trieu (via GitHub)" <gi...@apache.org>]

m-trieu commented on code in PR #30769:
URL: https://github.com/apache/beam/pull/30769#discussion_r1550659948


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runners/google-cloud-dataflow-java/worker/src/test/java/org/apache/beam/runners/dataflow/worker/LockFreeHistogramTest.java:
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@@ -0,0 +1,201 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF 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.apache.beam.runners.dataflow.worker;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.equalTo;
+
+import java.util.Optional;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import org.apache.beam.sdk.metrics.MetricName;
+import org.apache.beam.sdk.util.HistogramData;
+import org.apache.beam.sdk.values.KV;
+import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.primitives.ImmutableLongArray;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Tests for {@link LockFreeHistogram}. */
+@RunWith(JUnit4.class)
+public class LockFreeHistogramTest {
+
+  @Test
+  public void testUpdate_OverflowValues() {
+    HistogramData.BucketType bucketType = HistogramData.LinearBuckets.of(0, 10, 3);
+    LockFreeHistogram histogram =
+        new LockFreeHistogram(KV.of(MetricName.named("name", "namespace"), bucketType));
+    histogram.update(35, 40, 45);
+    Optional<LockFreeHistogram.Snapshot> snapshot = histogram.getSnapshotAndReset();
+
+    LockFreeHistogram.OutlierStatistic expectedOverflow =
+        LockFreeHistogram.OutlierStatistic.create(120.0, 3L);
+    LockFreeHistogram.OutlierStatistic expectedUnderflow = LockFreeHistogram.OutlierStatistic.EMPTY;
+    ImmutableLongArray expectedBuckets = ImmutableLongArray.of(0L, 0L, 0L);
+    LockFreeHistogram.Snapshot expectedSnapshot =
+        LockFreeHistogram.Snapshot.create(
+            expectedUnderflow, expectedOverflow, expectedBuckets, bucketType);
+
+    assertThat(snapshot.isPresent(), equalTo(true));
+    assertThat(snapshot.get(), equalTo(expectedSnapshot));
+    assertThat(snapshot.get().underflowStatistic().mean(), equalTo(0.0));
+    assertThat(snapshot.get().overflowStatistic(), equalTo(expectedOverflow));
+  }
+
+  @Test
+  public void testUpdate_UnderflowValues() {
+    HistogramData.BucketType bucketType = HistogramData.LinearBuckets.of(100, 10, 3);
+    LockFreeHistogram histogram =
+        new LockFreeHistogram(KV.of(MetricName.named("name", "namespace"), bucketType));
+    histogram.update(35, 40, 45);
+    Optional<LockFreeHistogram.Snapshot> snapshot = histogram.getSnapshotAndReset();
+
+    LockFreeHistogram.OutlierStatistic expectedUnderflow =
+        LockFreeHistogram.OutlierStatistic.create(120.0, 3L);
+    LockFreeHistogram.OutlierStatistic expectedOverflow = LockFreeHistogram.OutlierStatistic.EMPTY;
+    ImmutableLongArray expectedBuckets = ImmutableLongArray.of(0L, 0L, 0L);
+    LockFreeHistogram.Snapshot expectedSnapshot =
+        LockFreeHistogram.Snapshot.create(
+            expectedUnderflow, expectedOverflow, expectedBuckets, bucketType);
+
+    assertThat(snapshot.isPresent(), equalTo(true));
+    assertThat(snapshot.get(), equalTo(expectedSnapshot));
+    assertThat(snapshot.get().underflowStatistic(), equalTo(expectedUnderflow));
+  }
+
+  @Test
+  public void testUpdate_InBoundsValues() {
+    HistogramData.BucketType bucketType = HistogramData.LinearBuckets.of(0, 10, 3);
+    LockFreeHistogram histogram =
+        new LockFreeHistogram(KV.of(MetricName.named("name", "namespace"), bucketType));
+    histogram.update(5, 15, 25);
+    Optional<LockFreeHistogram.Snapshot> snapshot = histogram.getSnapshotAndReset();
+
+    LockFreeHistogram.OutlierStatistic expectedOverflow = LockFreeHistogram.OutlierStatistic.EMPTY;
+    LockFreeHistogram.OutlierStatistic expectedUnderflow = LockFreeHistogram.OutlierStatistic.EMPTY;
+    ImmutableLongArray expectedBuckets = ImmutableLongArray.of(1L, 1L, 1L);
+    LockFreeHistogram.Snapshot expectedSnapshot =
+        LockFreeHistogram.Snapshot.create(
+            expectedUnderflow, expectedOverflow, expectedBuckets, bucketType);
+
+    assertThat(snapshot.isPresent(), equalTo(true));
+    assertThat(snapshot.get(), equalTo(expectedSnapshot));
+  }
+
+  @Test
+  public void testUpdate_EmptySnapshot() {
+    HistogramData.BucketType bucketType = HistogramData.LinearBuckets.of(0, 10, 3);
+    LockFreeHistogram histogram =
+        new LockFreeHistogram(KV.of(MetricName.named("name", "namespace"), bucketType));
+    histogram.update(5, 15, 25);
+    Optional<LockFreeHistogram.Snapshot> snapshot_1 = histogram.getSnapshotAndReset();
+
+    assertThat(snapshot_1.isPresent(), equalTo(true));
+
+    Optional<LockFreeHistogram.Snapshot> snapshot_2 = histogram.getSnapshotAndReset();
+    assertThat(snapshot_2.isPresent(), equalTo(false));
+  }
+
+  /** A runnable records 200 values and then calls getSnapshotAndReset. */
+  private static class UpdateHistogramRunnable implements Runnable {
+    private final LockFreeHistogram histogram;
+    private final int val;
+    private final CountDownLatch startSignal;
+    private final CountDownLatch doneSignal;
+    private Optional<LockFreeHistogram.Snapshot> snapshot;
+
+    private static final long valuesRecorded = 200L;
+
+    public UpdateHistogramRunnable(
+        LockFreeHistogram histogram,
+        int val,
+        CountDownLatch startSignal,
+        CountDownLatch doneSignal) {
+      this.histogram = histogram;
+      this.val = val;
+      this.startSignal = startSignal;
+      this.doneSignal = doneSignal;
+      this.snapshot = Optional.empty();
+    }
+
+    @Override
+    public void run() {
+      try {
+        startSignal.await();
+      } catch (InterruptedException e) {
+        return;
+      }
+
+      for (long j = 0; j < valuesRecorded; j++) {
+        histogram.update(val);
+      }
+      snapshot = histogram.getSnapshotAndReset();
+
+      doneSignal.countDown();
+    }
+
+    public long totalCountInSnapshot() {
+      if (snapshot.isPresent()) {
+        return snapshot.get().totalCount();
+      }
+      return 0;
+    }
+
+    public static long numValuesRecorded() {
+      return valuesRecorded;
+    }
+  }
+
+  @Test
+  public void testUpdateAndSnapshots_MultipleThreads() {
+    int numRunnables = 200;
+    CountDownLatch startSignal = new CountDownLatch(1);
+    CountDownLatch doneSignal = new CountDownLatch(numRunnables);
+    ExecutorService executor = Executors.newFixedThreadPool(numRunnables);
+
+    HistogramData.BucketType bucketType = HistogramData.ExponentialBuckets.of(1, 10);
+    LockFreeHistogram histogram =
+        new LockFreeHistogram(KV.of(MetricName.named("name", "namespace"), bucketType));
+
+    UpdateHistogramRunnable[] runnables = new UpdateHistogramRunnable[numRunnables];
+    for (int i = 0; i < numRunnables; i++) {
+      runnables[i] = new UpdateHistogramRunnable(histogram, i, startSignal, doneSignal);
+      executor.execute(runnables[i]);

Review Comment:
   you will want to use executor.submit in the loop
   
   or create the array and then use executor.invokeAll() here
   
   call execute 1 at a time will still execute it sequentially on 1 thread since execute blocks



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