feat: Allow global otel configuration extraction (#505)

Signed-off-by: Kavindu Dodanduwa <[email protected]>
Co-authored-by: Giovanni Liva <[email protected]>
Co-authored-by: Todd Baert <[email protected]>

Author: 3 people

Diff for: providers/flagd/README.md

@@ -146,12 +146,21 @@ By default, the provider is configured to
 use [least recently used (lru)](https://commons.apache.org/proper/commons-collections/apidocs/org/apache/commons/collections4/map/LRUMap.html)
 caching with up to 1000 entries.
 
-### OpenTelemetry support (RPC only)
+### OpenTelemetry tracing (RPC only)
 
-OpenTelemetry support can be enabled either through [automatic instrumentation](https://opentelemetry.io/docs/instrumentation/java/automatic/) 
-or with [manual instrumentation](https://opentelemetry.io/docs/instrumentation/java/manual/). 
+flagd provider support OpenTelemetry traces for gRPC backed remote evaluations. 
 
-For manual instrumentation, flagd provider can be constructed with an `OpenTelemetry` instance.
+There are two ways you can configure OpenTelemetry for the provider,
+
+- [Using automatic instrumentation](https://opentelemetry.io/docs/instrumentation/java/automatic/)
+- [Using manual instrumentation](https://opentelemetry.io/docs/instrumentation/java/manual/)
+
+When using automatic instrumentation, traces for gRPC will be automatically added by the OpenTelemetry Java library.
+These traces however will not include extra attributes added when using manual instrumentation. 
+
+When using manual instrumentation, you have two options to construct flagd provider to enable traces.
+
+First(preferred) option is by constructing the provider with an OpenTelemetry instance,
 
 ```java
 FlagdOptions options = 
@@ -162,8 +171,18 @@ FlagdOptions options =
 FlagdProvider flagdProvider = new FlagdProvider(options);
 ```
 
-Please refer [OpenTelemetry example](https://opentelemetry.io/docs/instrumentation/java/manual/#example) for best 
-practice guideline.
+Second option is useful if you have set up a GlobalOpenTelemetry in your runtime.
+You can allow flagd to derive the OpenTelemetry instance by enabling `withGlobalTelemetry` option.
+
+```java
+FlagdOptions options =
+        FlagdOptions.builder()
+            .withGlobalTelemetry(true)
+            .build();
+
+FlagdProvider flagdProvider = new FlagdProvider(options);
+```
+
+Please refer [OpenTelemetry example](https://opentelemetry.io/docs/instrumentation/java/manual/#example) for best practice guideline.
 
-Telemetry configuration combined with [flagd telemetry ](https://github.com/open-feature/flagd/blob/main/docs/configuration/flagd_telemetry.md)
-allows distributed tracing.
+Provider telemetry combined with [flagd OpenTelemetry](https://flagd.dev/reference/monitoring/#opentelemetry) allows you to have distributed traces.

Diff for: providers/flagd/src/main/java/dev/openfeature/contrib/providers/flagd/FlagdOptions.java

@@ -1,5 +1,6 @@
 package dev.openfeature.contrib.providers.flagd;
 
+import io.opentelemetry.api.GlobalOpenTelemetry;
 import io.opentelemetry.api.OpenTelemetry;
 import lombok.Builder;
 import lombok.Getter;
@@ -151,5 +152,15 @@ public FlagdOptionsBuilder offlineFlagSourcePath(@Nonnull final String offlineFl
         private FlagdOptionsBuilder isOffline(final boolean isOffline) {
             return this;
         }
+
+        /**
+         * Enable OpenTelemetry instance extraction from GlobalOpenTelemetry. Note that, this is only useful if global
+         * configurations are registered.
+         */
+        public FlagdOptionsBuilder withGlobalTelemetry(final boolean b) {
+            this.openTelemetry = GlobalOpenTelemetry.get();
+
+            return this;
+        }
     }
 }

Diff for: providers/flagd/src/main/java/dev/openfeature/contrib/providers/flagd/resolver/grpc/strategy/ResolveFactory.java

@@ -8,13 +8,15 @@
 public final class ResolveFactory {
     /**
      * Factory method to initialize the resolving strategy.
+     *
      * @param options Options.
      * @return the ResolveStrategy based on the provided options.
      */
     public static ResolveStrategy getStrategy(FlagdOptions options) {
         if (options.getOpenTelemetry() != null) {
             return new TracedResolving(options.getOpenTelemetry());
         }
+
         return new SimpleResolving();
     }
 }

Diff for: providers/flagd/src/test/java/dev/openfeature/contrib/providers/flagd/resolver/grpc/strategy/ResolveFactoryTest.java

@@ -0,0 +1,50 @@
+package dev.openfeature.contrib.providers.flagd.resolver.grpc.strategy;
+
+import dev.openfeature.contrib.providers.flagd.FlagdOptions;
+import io.opentelemetry.api.OpenTelemetry;
+import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class ResolveFactoryTest {
+
+    @Test
+    public void simpleResolverAsDefault() {
+        // given
+        final FlagdOptions options = FlagdOptions.builder().build();
+
+        // when
+        final ResolveStrategy strategy = ResolveFactory.getStrategy(options);
+
+        // then
+        assertEquals(SimpleResolving.class, strategy.getClass());
+    }
+
+
+    @Test
+    public void tracedResolverWhenOTelSdkIsSet() {
+        // given
+        final OpenTelemetry telemetry = Mockito.mock(OpenTelemetry.class);
+
+        final FlagdOptions options = FlagdOptions.builder().openTelemetry(telemetry).build();
+
+        // when
+        final ResolveStrategy strategy = ResolveFactory.getStrategy(options);
+
+        // then
+        assertEquals(TracedResolving.class, strategy.getClass());
+    }
+
+    @Test
+    public void tracedResolverWhenGlobalTelemetryIsSet() {
+        // given
+        final FlagdOptions options = FlagdOptions.builder().withGlobalTelemetry(true).build();
+
+        // when
+        final ResolveStrategy strategy = ResolveFactory.getStrategy(options);
+
+        // then
+        assertEquals(TracedResolving.class, strategy.getClass());
+    }
+}

Diff for: providers/flagd/src/test/java/dev/openfeature/contrib/providers/flagd/resolver/grpc/strategy/TracedResolvingTest.java

@@ -1,8 +1,6 @@
 package dev.openfeature.contrib.providers.flagd.resolver.grpc.strategy;
 
-
 import com.google.protobuf.Message;
-import dev.openfeature.contrib.providers.flagd.resolver.grpc.strategy.TracedResolving;
 import dev.openfeature.flagd.grpc.Schema;
 import io.opentelemetry.api.OpenTelemetry;
 import io.opentelemetry.api.trace.Span;
@@ -20,7 +18,7 @@
 class TracedResolvingTest {
 
     @Test
-    public void basicTest(){
+    public void basicTest() {
         // given
         final String key = "flagA";
         final OpenTelemetry openTelemetry = mock(OpenTelemetry.class);