Add span based feature flags (#4831)

* Add scope based feature flags

* fix equals

* add serialization tests

* Create new reference on buffer clone

* add comment explaining the merge method

* optimize merge method

* make flag and result nullable params

* handle empty/noop buffer on merge and add tests for it

* optimize add method

* format; fix test

* Add rules for feature flags and mention in overview_dev

* Fix duplicate check

* Update sentry/src/main/java/io/sentry/SentryOptions.java

Co-authored-by: Lorenzo Cian <17258265+lcian@users.noreply.github.com>

* Format code

* Add feature flags to spans

* move feature flag buffer to span context; add e2e test

* e2e tests; fix POTel feature flags

* Format code

* test feature flag serialization from SentryTracer

* Format code

* fix e2e test assertions; handle null data map

* Format code

* changelog

* changelog

* nullable getFeatureFlags

* update changelog

* address pr review feedback

* Format code

* fix(otel): Copy active span on scope clone (#4878)

* Copy active span when cloning scope

* changelog

* api

---------

Co-authored-by: Lorenzo Cian <17258265+lcian@users.noreply.github.com>
Co-authored-by: Sentry Github Bot <bot+github-bot@sentry.io>

Author: 3 people

CHANGELOG.md

@@ -4,11 +4,15 @@
 
 ### Features
 
-- Add feature flags API ([#4812](https://github.com/getsentry/sentry-java/pull/4812))
+- Add feature flags API ([#4812](https://github.com/getsentry/sentry-java/pull/4812)) and ([#4831](https://github.com/getsentry/sentry-java/pull/4831))
   - You may now keep track of your feature flag evaluations and have them show up in Sentry.
-  - You may use top level API (`Sentry.addFeatureFlag("my-feature-flag", true);`) or `IScope` and `IScopes` API
+  - Top level API (`Sentry.addFeatureFlag("my-feature-flag", true);`) writes to scopes and the current span (if there is one)
+  - It is also possible to use API on `IScope`, `IScopes`, `ISpan` and `ITransaction` directly
   - Feature flag evaluations tracked on scope(s) will be added to any errors reported to Sentry.
-  - The SDK keeps the latest 100 evaluations from scope(s), replacing old entries as new evaluations are added.
+    - The SDK keeps the latest 100 evaluations from scope(s), replacing old entries as new evaluations are added.
+  - For feature flag evaluations tracked on spans:
+    - Only 10 evaluations are tracked per span, existing flags are updated but new ones exceeding the limit are ignored
+    - Spans do not inherit evaluations from their parent
 
 ### Fixes
 
@@ -20,6 +24,7 @@
 - Fix log count in client reports ([#4869](https://github.com/getsentry/sentry-java/pull/4869))
 - Fix profilerId propagation ([#4833](https://github.com/getsentry/sentry-java/pull/4833))
 - Fix profiling init for Spring and Spring Boot w Agent auto-init ([#4815](https://github.com/getsentry/sentry-java/pull/4815))
+- Copy active span on scope clone ([#4878](https://github.com/getsentry/sentry-java/pull/4878))
 
 ### Improvements
 

sentry-opentelemetry/sentry-opentelemetry-bootstrap/api/sentry-opentelemetry-bootstrap.api

@@ -43,6 +43,7 @@ public final class io/sentry/opentelemetry/OtelSpanFactory : io/sentry/ISpanFact
 
 public final class io/sentry/opentelemetry/OtelStrongRefSpanWrapper : io/sentry/opentelemetry/IOtelSpanWrapper {
 	public fun <init> (Lio/opentelemetry/api/trace/Span;Lio/sentry/opentelemetry/IOtelSpanWrapper;)V
+	public fun addFeatureFlag (Ljava/lang/String;Ljava/lang/Boolean;)V
 	public fun finish ()V
 	public fun finish (Lio/sentry/SpanStatus;)V
 	public fun finish (Lio/sentry/SpanStatus;Lio/sentry/SentryDate;)V
@@ -96,6 +97,7 @@ public final class io/sentry/opentelemetry/OtelStrongRefSpanWrapper : io/sentry/
 
 public final class io/sentry/opentelemetry/OtelTransactionSpanForwarder : io/sentry/ITransaction {
 	public fun <init> (Lio/sentry/opentelemetry/IOtelSpanWrapper;)V
+	public fun addFeatureFlag (Ljava/lang/String;Ljava/lang/Boolean;)V
 	public fun finish ()V
 	public fun finish (Lio/sentry/SpanStatus;)V
 	public fun finish (Lio/sentry/SpanStatus;Lio/sentry/SentryDate;)V

sentry-opentelemetry/sentry-opentelemetry-bootstrap/src/main/java/io/sentry/opentelemetry/OtelStrongRefSpanWrapper.java

@@ -310,4 +310,9 @@ public void setContext(@Nullable String key, @Nullable Object context) {
   public @Nullable Attributes getOpenTelemetrySpanAttributes() {
     return delegate.getOpenTelemetrySpanAttributes();
   }
+
+  @Override
+  public void addFeatureFlag(final @Nullable String flag, final @Nullable Boolean result) {
+    delegate.addFeatureFlag(flag, result);
+  }
 }

sentry-opentelemetry/sentry-opentelemetry-bootstrap/src/main/java/io/sentry/opentelemetry/OtelTransactionSpanForwarder.java

@@ -309,4 +309,9 @@ public void setName(@NotNull String name, @NotNull TransactionNameSource nameSou
     }
     return name;
   }
+
+  @Override
+  public void addFeatureFlag(final @Nullable String flag, final @Nullable Boolean result) {
+    rootSpan.addFeatureFlag(flag, result);
+  }
 }

sentry-opentelemetry/sentry-opentelemetry-core/api/sentry-opentelemetry-core.api

@@ -57,6 +57,7 @@ public final class io/sentry/opentelemetry/OtelSpanUtils {
 
 public final class io/sentry/opentelemetry/OtelSpanWrapper : io/sentry/opentelemetry/IOtelSpanWrapper {
 	public fun <init> (Lio/opentelemetry/sdk/trace/ReadWriteSpan;Lio/sentry/IScopes;Lio/sentry/SentryDate;Lio/sentry/TracesSamplingDecision;Lio/sentry/opentelemetry/IOtelSpanWrapper;Lio/sentry/SpanId;Lio/sentry/Baggage;)V
+	public fun addFeatureFlag (Ljava/lang/String;Ljava/lang/Boolean;)V
 	public fun finish ()V
 	public fun finish (Lio/sentry/SpanStatus;)V
 	public fun finish (Lio/sentry/SpanStatus;Lio/sentry/SentryDate;)V

sentry-opentelemetry/sentry-opentelemetry-core/src/main/java/io/sentry/opentelemetry/OtelSpanWrapper.java

@@ -505,6 +505,11 @@ public Map<String, MeasurementValue> getMeasurements() {
     return scopes;
   }
 
+  @Override
+  public void addFeatureFlag(final @Nullable String flag, final @Nullable Boolean result) {
+    context.addFeatureFlag(flag, result);
+  }
+
   @Override
   public @NotNull Context storeInContext(Context context) {
     final @Nullable ReadWriteSpan otelSpan = getSpan();

sentry-opentelemetry/sentry-opentelemetry-core/src/main/java/io/sentry/opentelemetry/SentrySpanExporter.java

@@ -33,7 +33,10 @@
 import io.sentry.SpanStatus;
 import io.sentry.TransactionContext;
 import io.sentry.TransactionOptions;
+import io.sentry.featureflags.IFeatureFlagBuffer;
 import io.sentry.protocol.Contexts;
+import io.sentry.protocol.FeatureFlag;
+import io.sentry.protocol.FeatureFlags;
 import io.sentry.protocol.SentryId;
 import io.sentry.protocol.TransactionNameSource;
 import java.util.Arrays;
@@ -260,6 +263,16 @@ private void transferSpanDetails(
         targetSpan.setData(entry.getKey(), entry.getValue());
       }
 
+      final @NotNull SpanContext spanContext = sourceSpan.getSpanContext();
+      final @NotNull IFeatureFlagBuffer featureFlagBuffer = spanContext.getFeatureFlagBuffer();
+      final @Nullable FeatureFlags featureFlags = featureFlagBuffer.getFeatureFlags();
+      if (featureFlags != null) {
+        for (FeatureFlag featureFlag : featureFlags.getValues()) {
+          targetSpan.setData(
+              FeatureFlag.DATA_PREFIX + featureFlag.getFlag(), featureFlag.getResult());
+        }
+      }
+
       final @NotNull Map<String, String> tags = sourceSpan.getTags();
       for (Map.Entry<String, String> entry : tags.entrySet()) {
         targetSpan.setTag(entry.getKey(), entry.getValue());

sentry-samples/sentry-samples-spring-boot-4-opentelemetry-noagent/src/main/java/io/sentry/samples/spring/boot4/PersonController.java

@@ -31,12 +31,13 @@ public PersonController(PersonService personService, Tracer tracer) {
   @GetMapping("{id}")
   @WithSpan("personSpanThroughOtelAnnotation")
   Person person(@PathVariable Long id) {
+    Sentry.addFeatureFlag("outer-feature-flag", true);
     Span span = tracer.spanBuilder("spanCreatedThroughOtelApi").startSpan();
     try (final @NotNull Scope spanScope = span.makeCurrent()) {
       Sentry.logger().warn("warn Sentry logging");
       Sentry.logger().error("error Sentry logging");
       Sentry.logger().info("hello %s %s", "there", "world!");
-      Sentry.addFeatureFlag("my-feature-flag", true);
+      Sentry.addFeatureFlag("inner-feature-flag", true);
       ISpan currentSpan = Sentry.getSpan();
       ISpan sentrySpan = currentSpan.startChild("spanCreatedThroughSentryApi");
       try {

sentry-samples/sentry-samples-spring-boot-4-opentelemetry-noagent/src/test/kotlin/io/sentry/systemtest/PersonSystemTest.kt

@@ -1,5 +1,6 @@
 package io.sentry.systemtest
 
+import io.sentry.protocol.FeatureFlag
 import io.sentry.systemtest.util.TestHelper
 import kotlin.test.Test
 import kotlin.test.assertEquals
@@ -22,17 +23,31 @@ class PersonSystemTest {
 
     testHelper.ensureErrorReceived { event ->
       event.message?.formatted == "Trying person with id=1" &&
-        testHelper.doesEventHaveFlag(event, "my-feature-flag", true)
+        testHelper.doesEventHaveFlag(event, "inner-feature-flag", true)
     }
 
     testHelper.ensureErrorReceived { event ->
       testHelper.doesEventHaveExceptionMessage(event, "Something went wrong [id=1]") &&
-        testHelper.doesEventHaveFlag(event, "my-feature-flag", true)
+        testHelper.doesEventHaveFlag(event, "inner-feature-flag", true)
     }
 
     testHelper.ensureTransactionReceived { transaction, envelopeHeader ->
-      testHelper.doesTransactionContainSpanWithOp(transaction, "spanCreatedThroughOtelApi") &&
-        testHelper.doesTransactionContainSpanWithOp(transaction, "spanCreatedThroughSentryApi")
+      testHelper.doesTransactionHave(transaction, op = "http.server") &&
+        testHelper.doesTransactionHaveSpanWith(
+          transaction,
+          op = "personSpanThroughOtelAnnotation",
+          featureFlag = FeatureFlag("flag.evaluation.outer-feature-flag", true),
+        ) &&
+        testHelper.doesTransactionHaveSpanWith(
+          transaction,
+          op = "spanCreatedThroughOtelApi",
+          featureFlag = FeatureFlag("flag.evaluation.inner-feature-flag", true),
+        ) &&
+        testHelper.doesTransactionHaveSpanWith(
+          transaction,
+          op = "spanCreatedThroughSentryApi",
+          noFeatureFlags = true,
+        )
     }
 
     Thread.sleep(10000)

sentry-samples/sentry-samples-spring-boot-4-opentelemetry/src/main/java/io/sentry/samples/spring/boot4/PersonController.java

@@ -29,6 +29,7 @@ public PersonController(PersonService personService, Tracer tracer) {
 
   @GetMapping("{id}")
   Person person(@PathVariable Long id) {
+    Sentry.addFeatureFlag("transaction-feature-flag", true);
     Span span = tracer.spanBuilder("spanCreatedThroughOtelApi").startSpan();
     try (final @NotNull Scope spanScope = span.makeCurrent()) {
       Sentry.logger().warn("warn Sentry logging");