Add OTel span events for commit retry sleeps

Useful for analysing Nessie behaviour under load.

versioned/storage/common/build.gradle.kts

@@ -52,6 +52,9 @@ dependencies {
   testImplementation(platform(libs.junit.bom))
   testImplementation(libs.bundles.junit.testing)
 
+  testImplementation(platform(libs.opentelemetry.bom))
+  testImplementation("io.opentelemetry:opentelemetry-sdk-testing")
+
   testCompileOnly(libs.immutables.builder)
   testCompileOnly(libs.immutables.value.annotations)
   testAnnotationProcessor(libs.immutables.value.processor)

versioned/storage/common/src/main/java/org/projectnessie/versioned/storage/common/logic/CommitRetry.java

@@ -20,6 +20,9 @@
 import static org.projectnessie.versioned.storage.common.logic.CommitRetry.TryLoopState.newTryLoopState;
 
 import com.google.common.annotations.VisibleForTesting;
+import io.opentelemetry.api.common.AttributeKey;
+import io.opentelemetry.api.common.Attributes;
+import io.opentelemetry.api.trace.Span;
 import java.util.Optional;
 import java.util.concurrent.ThreadLocalRandom;
 import javax.annotation.Nonnull;
@@ -31,6 +34,10 @@
 
 public class CommitRetry {
 
+  private static final String OTEL_SLEEP_EVENT_NAME = "nessie.commit-retry.sleep";
+  private static final AttributeKey<Long> OTEL_SLEEP_EVENT_TIME_KEY =
+      AttributeKey.longKey("nessie.commit-retry.sleep.duration-millis");
+
   private CommitRetry() {}
 
   public static <T> T commitRetry(Persist persist, CommitAttempt<T> attempt)
@@ -168,6 +175,9 @@ private void sleepAndBackoff(long totalElapsed, long attemptElapsed) {
       // consider the already elapsed time of the last attempt
       sleepMillis = Math.max(1L, sleepMillis - NANOSECONDS.toMillis(attemptElapsed));
 
+      Span.current()
+          .addEvent(OTEL_SLEEP_EVENT_NAME, Attributes.of(OTEL_SLEEP_EVENT_TIME_KEY, sleepMillis));
+
       monotonicClock.sleepMillis(sleepMillis);
 
       upper = upper * 2;

versioned/storage/common/src/test/java/org/projectnessie/versioned/storage/common/logic/TestCommitRetry.java

@@ -17,6 +17,7 @@
 
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static org.assertj.core.api.InstanceOfAssertFactories.type;
+import static org.junit.jupiter.api.AssertionFailureBuilder.assertionFailure;
 import static org.mockito.ArgumentMatchers.anyLong;
 import static org.mockito.ArgumentMatchers.longThat;
 import static org.mockito.Mockito.clearInvocations;
@@ -29,14 +30,24 @@
 import static org.mockito.Mockito.when;
 import static org.projectnessie.versioned.storage.common.logic.CommitRetry.commitRetry;
 
+import io.opentelemetry.api.common.AttributeKey;
+import io.opentelemetry.api.trace.Span;
+import io.opentelemetry.context.Scope;
+import io.opentelemetry.sdk.testing.junit5.OpenTelemetryExtension;
+import io.opentelemetry.sdk.trace.data.EventData;
+import io.opentelemetry.sdk.trace.data.SpanData;
 import java.util.Arrays;
+import java.util.List;
+import java.util.Optional;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicReference;
 import org.assertj.core.api.SoftAssertions;
 import org.assertj.core.api.junit.jupiter.InjectSoftAssertions;
 import org.assertj.core.api.junit.jupiter.SoftAssertionsExtension;
+import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
+import org.junit.jupiter.api.extension.RegisterExtension;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.ValueSource;
 import org.mockito.ArgumentMatcher;
@@ -347,6 +358,45 @@ public void retriesOutOfTime(int retries) {
     soft.assertThat(tryLoopState.retry(0L)).isFalse();
   }
 
+  @Nested
+  class Telemetry {
+    @RegisterExtension public final OpenTelemetryExtension otel = OpenTelemetryExtension.create();
+
+    private List<EventData> eventsFrom(Runnable action) {
+      Span span = otel.getOpenTelemetry().getTracer("test").spanBuilder("test").startSpan();
+      try (Scope ignored = span.makeCurrent()) {
+        action.run();
+      }
+      span.end();
+
+      String spanId = span.getSpanContext().getSpanId();
+      Optional<SpanData> spanData =
+          otel.getSpans().stream().filter(s -> s.getSpanId().equals(spanId)).findFirst();
+
+      return spanData
+          .orElseThrow(
+              () ->
+                  assertionFailure()
+                      .actual(otel.getSpans())
+                      .message("Expected Span not found: " + spanId)
+                      .build())
+          .getEvents();
+    }
+
+    @Test
+    void commitRetryEvents() {
+      List<EventData> events = eventsFrom(TestCommitRetry.this::commitRetrySuccessAfterRetry);
+      // 1 sleep due to failure induced by commitRetrySuccessAfterRetry()
+      soft.assertThat(events).hasSize(1);
+      soft.assertThat(events.get(0).getName()).isEqualTo("nessie.commit-retry.sleep");
+      soft.assertThat(events)
+          .extracting(
+              e ->
+                  e.getAttributes().asMap().keySet().stream().map(AttributeKey::getKey).findFirst())
+          .containsExactly(Optional.of("nessie.commit-retry.sleep.duration-millis"));
+    }
+  }
+
   MonotonicClock mockedClock(int retries) {
     Long[] times = new Long[retries];
     Arrays.fill(times, 0L);