Preserve span order (#8017)

On jdk8 tests occasionally fail when spans starting on the same
millisecond get reordered. As we eventually sort the spans by start time
we can't get the initial oder back when the start time is the same for
these spans. Hopefully preserving the initial order reduces such
flakiness.

Author: laurit

testing-common/src/main/java/io/opentelemetry/instrumentation/testing/util/TelemetryDataUtil.java

@@ -14,7 +14,7 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Comparator;
-import java.util.HashMap;
+import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.TimeUnit;
@@ -37,7 +37,9 @@ public static Comparator<List<SpanData>> orderByRootSpanName(String... names) {
   public static List<List<SpanData>> groupTraces(List<SpanData> spans) {
     List<List<SpanData>> traces =
         new ArrayList<>(
-            spans.stream().collect(Collectors.groupingBy(SpanData::getTraceId)).values());
+            spans.stream()
+                .collect(Collectors.groupingBy(SpanData::getTraceId, LinkedHashMap::new, toList()))
+                .values());
     sortTraces(traces);
     for (int i = 0; i < traces.size(); i++) {
       List<SpanData> trace = traces.get(i);
@@ -107,7 +109,7 @@ private static long getMinSpanOrder(List<SpanData> spans) {
   @SuppressWarnings("UnstableApiUsage")
   private static List<SpanData> sort(List<SpanData> trace) {
 
-    Map<String, Node> lookup = new HashMap<>();
+    Map<String, Node> lookup = new LinkedHashMap<>();
     for (SpanData span : trace) {
       lookup.put(span.getSpanId(), new Node(span));
     }

testing-common/src/test/java/io/opentelemetry/instrumentation/testing/util/TelemetryDataUtilTest.java

@@ -0,0 +1,90 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.instrumentation.testing.util;
+
+import static io.opentelemetry.sdk.testing.assertj.TracesAssert.assertThat;
+
+import io.opentelemetry.api.trace.SpanContext;
+import io.opentelemetry.api.trace.SpanId;
+import io.opentelemetry.api.trace.SpanKind;
+import io.opentelemetry.api.trace.TraceFlags;
+import io.opentelemetry.api.trace.TraceId;
+import io.opentelemetry.api.trace.TraceState;
+import io.opentelemetry.sdk.testing.assertj.SpanDataAssert;
+import io.opentelemetry.sdk.testing.assertj.TraceAssert;
+import io.opentelemetry.sdk.testing.trace.TestSpanData;
+import io.opentelemetry.sdk.trace.data.SpanData;
+import io.opentelemetry.sdk.trace.data.StatusData;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Consumer;
+import org.junit.jupiter.api.Test;
+
+public class TelemetryDataUtilTest {
+
+  @Test
+  void testTraceOrderPreserved() {
+    List<SpanData> spans = new ArrayList<>();
+    for (int i = 1; i <= 10; i++) {
+      spans.add(
+          TestSpanData.builder()
+              .setName("trace" + i)
+              .setSpanContext(
+                  SpanContext.create(
+                      TraceId.fromLongs(0, i),
+                      SpanId.fromLong(i),
+                      TraceFlags.getDefault(),
+                      TraceState.getDefault()))
+              .setKind(SpanKind.CLIENT)
+              .setStatus(StatusData.unset())
+              .setHasEnded(true)
+              .setStartEpochNanos(1678338770194000000L)
+              .setEndEpochNanos(1678338770196419884L)
+              .build());
+    }
+
+    List<Consumer<TraceAssert>> asserts = new ArrayList<>();
+    for (int i = 1; i <= 10; i++) {
+      String spanName = "trace" + i;
+      asserts.add(trace -> trace.hasSpansSatisfyingExactly(span -> span.hasName(spanName)));
+    }
+
+    List<List<SpanData>> result = TelemetryDataUtil.groupTraces(spans);
+    assertThat(result).hasTracesSatisfyingExactly(asserts);
+  }
+
+  @Test
+  void testSpanOrderPreserved() {
+    List<SpanData> spans = new ArrayList<>();
+    for (int i = 1; i <= 10; i++) {
+      spans.add(
+          TestSpanData.builder()
+              .setName("span" + i)
+              .setSpanContext(
+                  SpanContext.create(
+                      TraceId.fromLongs(0, 1),
+                      SpanId.fromLong(i),
+                      TraceFlags.getDefault(),
+                      TraceState.getDefault()))
+              .setKind(SpanKind.CLIENT)
+              .setStatus(StatusData.unset())
+              .setHasEnded(true)
+              .setStartEpochNanos(1678338770194000000L)
+              .setEndEpochNanos(1678338770196419884L)
+              .build());
+    }
+
+    List<Consumer<SpanDataAssert>> asserts = new ArrayList<>();
+    for (int i = 1; i <= 10; i++) {
+      String spanName = "span" + i;
+      asserts.add(span -> span.hasName(spanName));
+    }
+
+    List<List<SpanData>> result = TelemetryDataUtil.groupTraces(spans);
+    assertThat(result)
+        .hasTracesSatisfyingExactly(trace -> trace.hasSpansSatisfyingExactly(asserts));
+  }
+}