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feat: add spec compliant otel hook (#169)
feat: add spec compliant otel hook Signed-off-by: thiyagu06 <[email protected]>
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‎hooks/README.md

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# OpenFeature Java Hooks
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Hooks are a mechanism whereby application developers can add arbitrary behavior to flag evaluation. They operate similarly to middleware in many web frameworks. Please see the [spec](https://github.com/open-feature/spec/blob/main/specification/sections/04-hooks.md) for more details.
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The OpenTelemetry hook for OpenFeature provides
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a [spec compliant] (https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/feature-flags.md)
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way to automatically add a feature flag
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evaluation to a span as a span event. This can be used to determine the impact a feature has on a request,
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enabling enhanced observability use cases, such as A/B testing or progressive feature releases.
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## Installation
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<!-- x-release-please-start-version -->
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```xml
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<dependency>
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<groupId>dev.openfeature.contrib.hooks</groupId>
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<artifactId>otel</artifactId>
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<version>0.4.0</version>
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</dependency>
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```
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<!-- x-release-please-end-version -->
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## Usage
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OpenFeature provider various ways to register hooks. The location that a hook is registered affects when the hook is
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run. It's recommended to register the `OpenTelemetryHook` globally in most situations, but it's possible to only enable
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the hook on specific clients. You should **never** register the `OpenTelemetryHook` globally and on a client.
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```
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OpenFeatureAPI.getInstance().addHooks(new OpenTelemetryHook());
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```

‎hooks/open-telemetry/pom.xml

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<dependencies>
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<!-- we inherent dev.openfeature.javasdk and the test dependencies from the parent pom -->
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<dependency>
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<groupId>io.opentelemetry</groupId>
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<artifactId>opentelemetry-sdk</artifactId>
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</dependency>
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</dependencies>
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<dependencyManagement>
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<dependencies>
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<dependency>
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<groupId>io.opentelemetry</groupId>
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<artifactId>opentelemetry-bom</artifactId>
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<version>1.20.1</version>
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<type>pom</type>
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<scope>import</scope>
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</dependency>
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</dependencies>
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</dependencyManagement>
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</project>

‎hooks/open-telemetry/src/main/java/dev/openfeature/contrib/hooks/otel/OpenTelemetryHook.java

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package dev.openfeature.contrib.hooks.otel;
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import dev.openfeature.sdk.Client;
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import dev.openfeature.sdk.NoOpProvider;
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import dev.openfeature.sdk.OpenFeatureAPI;
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import dev.openfeature.sdk.FlagEvaluationDetails;
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import dev.openfeature.sdk.Hook;
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import dev.openfeature.sdk.HookContext;
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import io.opentelemetry.api.common.AttributeKey;
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import io.opentelemetry.api.common.Attributes;
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import io.opentelemetry.api.trace.Span;
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/**
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* A placeholder.
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import java.util.Map;
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/**
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* The OpenTelemetry hook provides a way to automatically add a feature flag evaluation to a span as a span event.
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* Refer to <a href="https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/feature-flags.md">OpenTelemetry</a>
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*/
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public class OpenTelemetryHook {
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/**
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public class OpenTelemetryHook implements Hook {
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private static final String EVENT_NAME = "feature_flag";
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private final AttributeKey<String> flagKeyAttributeKey = AttributeKey.stringKey(EVENT_NAME + ".flag_key");
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private final AttributeKey<String> providerNameAttributeKey = AttributeKey.stringKey(EVENT_NAME + ".provider_name");
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private final AttributeKey<String> variantAttributeKey = AttributeKey.stringKey(EVENT_NAME + ".variant");
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/**
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* Create a new OpenTelemetryHook instance.
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*/
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public OpenTelemetryHook() {
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}
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/**
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* A test method...
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/**
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* Records the event in the current span after the successful flag evaluation.
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*
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* @return {boolean}
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* @param ctx Information about the particular flag evaluation
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* @param details Information about how the flag was resolved, including any resolved values.
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* @param hints An immutable mapping of data for users to communicate to the hooks.
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*/
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public static boolean test() {
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OpenFeatureAPI.getInstance().setProvider(new NoOpProvider());
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Client client = OpenFeatureAPI.getInstance().getClient();
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return client.getBooleanValue("test2", true);
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@Override
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public void after(HookContext ctx, FlagEvaluationDetails details, Map hints) {
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Span currentSpan = Span.current();
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if (currentSpan != null) {
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String variant = details.getVariant() != null ? details.getVariant() : String.valueOf(details.getValue());
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Attributes attributes = Attributes.of(
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flagKeyAttributeKey, ctx.getFlagKey(),
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providerNameAttributeKey, ctx.getProviderMetadata().getName(),
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variantAttributeKey, variant);
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currentSpan.addEvent(EVENT_NAME, attributes);
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}
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}
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/**
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* Records the error details in the current span after the flag evaluation has processed abnormally.
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*
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* @param ctx Information about the particular flag evaluation
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* @param error The exception that was thrown.
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* @param hints An immutable mapping of data for users to communicate to the hooks.
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*/
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@Override
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public void error(HookContext ctx, Exception error, Map hints) {
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Span currentSpan = Span.current();
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if (currentSpan != null) {
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Attributes attributes = Attributes.of(
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flagKeyAttributeKey, ctx.getFlagKey(),
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providerNameAttributeKey, ctx.getProviderMetadata().getName());
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currentSpan.recordException(error, attributes);
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}
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}
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}

‎hooks/open-telemetry/src/test/java/dev/openfeature/contrib/hooks/otel/OpenTelemetryHookTest.java

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package dev.openfeature.contrib.hooks.otel;
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import static org.assertj.core.api.Assertions.assertThat;
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import dev.openfeature.sdk.FlagEvaluationDetails;
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import dev.openfeature.sdk.FlagValueType;
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import dev.openfeature.sdk.HookContext;
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import dev.openfeature.sdk.MutableContext;
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import io.opentelemetry.api.common.AttributeKey;
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import io.opentelemetry.api.common.Attributes;
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import io.opentelemetry.api.trace.Span;
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import org.junit.jupiter.api.AfterAll;
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import org.junit.jupiter.api.BeforeAll;
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import org.junit.jupiter.api.DisplayName;
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import org.junit.jupiter.api.Test;
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import org.junit.jupiter.api.extension.ExtendWith;
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import org.mockito.Mock;
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import org.mockito.MockedStatic;
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import org.mockito.Mockito;
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import org.mockito.MockitoAnnotations;
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import org.mockito.internal.matchers.Any;
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import org.mockito.junit.jupiter.MockitoExtension;
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import static org.mockito.ArgumentMatchers.any;
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import static org.mockito.ArgumentMatchers.anyString;
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import static org.mockito.Mockito.mock;
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import static org.mockito.Mockito.mockStatic;
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import static org.mockito.Mockito.verify;
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import static org.mockito.Mockito.verifyNoInteractions;
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@ExtendWith(MockitoExtension.class)
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class OpenTelemetryHookTest {
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private OpenTelemetryHook openTelemetryHook = new OpenTelemetryHook();
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private final AttributeKey<String> flagKeyAttributeKey = AttributeKey.stringKey("feature_flag.flag_key");
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private final AttributeKey<String> providerNameAttributeKey = AttributeKey.stringKey("feature_flag.provider_name");
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private final AttributeKey<String> variantAttributeKey = AttributeKey.stringKey("feature_flag.variant");
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private static MockedStatic<Span> mockedSpan;
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@Mock private Span span;
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private HookContext<String> hookContext = HookContext.<String>builder()
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.flagKey("test_key")
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.type(FlagValueType.STRING)
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.providerMetadata(() -> "test provider")
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.ctx(new MutableContext())
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.defaultValue("default")
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.build();
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@BeforeAll
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public static void init() {
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mockedSpan = mockStatic(Span.class);
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}
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@AfterAll
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public static void close() {
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mockedSpan.close();
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}
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@Test
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@DisplayName("a simple test.")
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void test() {
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assertThat(OpenTelemetryHook.test()).isEqualTo(true);
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@DisplayName("should add an event in span during after method execution")
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void should_add_event_in_span_during_after_method_execution() {
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FlagEvaluationDetails<String> details = FlagEvaluationDetails.<String>builder()
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.variant("test_variant")
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.value("variant_value")
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.build();
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mockedSpan.when(Span::current).thenReturn(span);
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openTelemetryHook.after(hookContext, details, null);
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Attributes expectedAttr = Attributes.of(flagKeyAttributeKey, "test_key",
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providerNameAttributeKey, "test provider",
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variantAttributeKey, "test_variant");
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verify(span).addEvent("feature_flag", expectedAttr);
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}
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}
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@Test
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@DisplayName("attribute should fallback to value field when variant is null")
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void attribute_should_fallback_to_value_field_when_variant_is_null() {
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FlagEvaluationDetails<String> details = FlagEvaluationDetails.<String>builder()
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.value("variant_value")
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.build();
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mockedSpan.when(Span::current).thenReturn(span);
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openTelemetryHook.after(hookContext, details, null);
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Attributes expectedAttr = Attributes.of(flagKeyAttributeKey, "test_key",
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providerNameAttributeKey, "test provider",
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variantAttributeKey, "variant_value");
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verify(span).addEvent("feature_flag", expectedAttr);
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}
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@Test
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@DisplayName("should not call addEvent because there is no active span")
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void should_not_call_add_event_when_no_active_span() {
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HookContext<String> hookContext = HookContext.<String>builder()
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.flagKey("test_key")
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.type(FlagValueType.STRING)
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.providerMetadata(() -> "test provider")
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.ctx(new MutableContext())
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.defaultValue("default")
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.build();
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FlagEvaluationDetails<String> details = FlagEvaluationDetails.<String>builder()
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.variant(null)
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.value("variant_value")
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.build();
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mockedSpan.when(Span::current).thenReturn(null);
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openTelemetryHook.after(hookContext, details, null);
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verifyNoInteractions(span);
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}
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@Test
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@DisplayName("should record an exception in span during error method execution")
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void should_record_exception_in_span_during_error_method_execution() {
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RuntimeException runtimeException = new RuntimeException("could not resolve the flag");
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mockedSpan.when(Span::current).thenReturn(span);
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openTelemetryHook.error(hookContext, runtimeException, null);
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Attributes expectedAttr = Attributes.of(flagKeyAttributeKey, "test_key",
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providerNameAttributeKey, "test provider");
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verify(span).recordException(runtimeException, expectedAttr);
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}
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@Test
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@DisplayName("should not call recordException because there is no active span")
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void should_not_call_record_exception_when_no_active_span() {
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RuntimeException runtimeException = new RuntimeException("could not resolve the flag");
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mockedSpan.when(Span::current).thenReturn(null);
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openTelemetryHook.error(hookContext, runtimeException, null);
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verifyNoInteractions(span);
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}
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}

‎pom.xml

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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.mockito</groupId>
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<artifactId>mockito-junit-jupiter</artifactId>
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<version>4.10.0</version>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.mockito</groupId>
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<artifactId>mockito-inline</artifactId>

‎release-please-config.json

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"bump-patch-for-minor-pre-major": true,
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"versioning": "default",
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"extra-files": [
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"pom.xml"
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"pom.xml",
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"README.md"
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]
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}
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}

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