From 5c886255671ea4a41aeccba5fea8ba5001dfd40c Mon Sep 17 00:00:00 2001
From: Weian Deng <wdeng@walmart.com>
Date: Sun, 16 Mar 2025 19:12:33 -0700
Subject: [PATCH] #13295: Instrumenter.getNanos() returns non-epoch timestamp.

---
 .../api/instrumenter/Instrumenter.java        |  2 +-
 .../api/instrumenter/InstrumenterTest.java    | 42 +++++++++++++++++++
 2 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/instrumentation-api/src/main/java/io/opentelemetry/instrumentation/api/instrumenter/Instrumenter.java b/instrumentation-api/src/main/java/io/opentelemetry/instrumentation/api/instrumenter/Instrumenter.java
index a51990317067..bbe02ba4d37e 100644
--- a/instrumentation-api/src/main/java/io/opentelemetry/instrumentation/api/instrumenter/Instrumenter.java
+++ b/instrumentation-api/src/main/java/io/opentelemetry/instrumentation/api/instrumenter/Instrumenter.java
@@ -266,7 +266,7 @@ private void doEnd(
 
   private static long getNanos(@Nullable Instant time) {
     if (time == null) {
-      return System.nanoTime();
+      time = Instant.now();
     }
     return TimeUnit.SECONDS.toNanos(time.getEpochSecond()) + time.getNano();
   }
diff --git a/instrumentation-api/src/test/java/io/opentelemetry/instrumentation/api/instrumenter/InstrumenterTest.java b/instrumentation-api/src/test/java/io/opentelemetry/instrumentation/api/instrumenter/InstrumenterTest.java
index fb9ae8622d8d..9b7558a23294 100644
--- a/instrumentation-api/src/test/java/io/opentelemetry/instrumentation/api/instrumenter/InstrumenterTest.java
+++ b/instrumentation-api/src/test/java/io/opentelemetry/instrumentation/api/instrumenter/InstrumenterTest.java
@@ -25,6 +25,7 @@
 import io.opentelemetry.context.Context;
 import io.opentelemetry.context.ContextKey;
 import io.opentelemetry.context.propagation.TextMapGetter;
+import io.opentelemetry.instrumentation.api.internal.InstrumenterUtil;
 import io.opentelemetry.instrumentation.api.internal.SchemaUrlProvider;
 import io.opentelemetry.instrumentation.api.internal.SpanKey;
 import io.opentelemetry.instrumentation.api.internal.SpanKeyProvider;
@@ -32,6 +33,7 @@
 import io.opentelemetry.sdk.testing.junit5.OpenTelemetryExtension;
 import io.opentelemetry.sdk.trace.data.LinkData;
 import io.opentelemetry.sdk.trace.data.StatusData;
+import java.time.Instant;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
@@ -39,6 +41,7 @@
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 import javax.annotation.Nullable;
+import org.assertj.core.api.Assertions;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.junit.jupiter.api.extension.RegisterExtension;
@@ -581,6 +584,45 @@ void instrumentationVersion_default() {
                     span -> span.hasName("span").hasInstrumentationScopeInfo(expectedLibraryInfo)));
   }
 
+  @Test
+  void instrumenterGetNanosWithNullArgument() {
+    AtomicReference<Long> endTime = new AtomicReference<>();
+    OperationListener operationListener =
+        new OperationListener() {
+          @Override
+          public Context onStart(Context context, Attributes startAttributes, long startNanos) {
+            return context;
+          }
+
+          @Override
+          public void onEnd(Context context, Attributes endAttributes, long endNanos) {
+            endTime.set(endNanos);
+          }
+        };
+
+    InstrumenterBuilder<Map<String, String>, Map<String, String>> builder =
+        Instrumenter.builder(
+            otelTesting.getOpenTelemetry(), "test-instrumentation", name -> "span");
+    builder.addOperationListener(operationListener);
+    InstrumenterUtil.propagateOperationListenersToOnEnd(builder);
+
+    Instant startTime = Instant.now();
+    Instrumenter<Map<String, String>, Map<String, String>> instrumenter =
+        builder.buildInstrumenter();
+    InstrumenterUtil.startAndEnd(
+        instrumenter, Context.root(), emptyMap(), emptyMap(), null, startTime, null);
+
+    otelTesting
+        .assertTraces()
+        .hasTracesSatisfyingExactly(
+            trace ->
+                trace.hasSpansSatisfyingExactly(span -> span.hasName("span").startsAt(startTime)));
+    System.out.printf(
+        "Epoche second of start: %d and end: %d\n",
+        startTime.getEpochSecond(), endTime.get() / 1_000_000_000);
+    Assertions.assertThat(endTime.get() / 1_000_000_000 == startTime.getEpochSecond()).isTrue();
+  }
+
   @Test
   void instrumentationVersion_custom() {
     Instrumenter<Map<String, String>, Map<String, String>> instrumenter =