Add autoconfiguration for client side observation interceptor

[resolves #51]

Signed-off-by: Jonas Bjørge Andersen <dev@jonasandersen.no>

spring-grpc-docs/src/main/antora/modules/ROOT/pages/client.adoc

@@ -131,3 +131,7 @@ However, by setting the `mergeWithGlobalInterceptors` parameter on the channel f
 You can use this option if you want to add a per-client interceptor between global interceptors.
 
 IMPORTANT: The per-channel interceptors you pass in must either be bean instances marked with `@Order` or regular objects that implement the `Ordered` interface to be properly merged/ordered with the global interceptors.
+
+== Observability
+
+Spring gRPC provides an autoconfigured interceptor that can be used to provide observability to your gRPC clients.

spring-grpc-spring-boot-autoconfigure/src/main/java/org/springframework/grpc/autoconfigure/client/GrpcClientObservationAutoConfiguration.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2024-2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.grpc.autoconfigure.client;
+
+import io.micrometer.core.instrument.binder.grpc.ObservationGrpcClientInterceptor;
+import io.micrometer.observation.ObservationRegistry;
+import org.springframework.boot.autoconfigure.AutoConfiguration;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
+import org.springframework.context.annotation.Bean;
+import org.springframework.grpc.client.GlobalClientInterceptor;
+
+@AutoConfiguration(
+		afterName = "org.springframework.boot.actuate.autoconfigure.observation.ObservationAutoConfiguration")
+@ConditionalOnClass({ ObservationRegistry.class, ObservationGrpcClientInterceptor.class })
+@ConditionalOnBean(ObservationRegistry.class)
+@ConditionalOnProperty(name = "spring.grpc.client.observation.enabled", havingValue = "true", matchIfMissing = true)
+
+public class GrpcClientObservationAutoConfiguration {
+
+	@Bean
+	@GlobalClientInterceptor
+	ObservationGrpcClientInterceptor observationGrpcClientInterceptor(ObservationRegistry observationRegistry) {
+		return new ObservationGrpcClientInterceptor(observationRegistry);
+	}
+
+}

spring-grpc-spring-boot-autoconfigure/src/main/resources/META-INF/additional-spring-configuration-metadata.json

@@ -22,7 +22,12 @@
       "type": "java.lang.Boolean",
       "description": "Whether to enable Observations on the server.",
       "defaultValue": true
-
+    },
+    {
+      "name": "spring.grpc.client.observations.enabled",
+      "type": "java.lang.Boolean",
+      "description": "Whether to enable Observations on the client.",
+      "defaultValue": true
     }
   ]
 }

spring-grpc-spring-boot-autoconfigure/src/main/resources/META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports

@@ -1,4 +1,5 @@
 org.springframework.grpc.autoconfigure.client.GrpcClientAutoConfiguration
+org.springframework.grpc.autoconfigure.client.GrpcClientObservationAutoConfiguration
 org.springframework.grpc.autoconfigure.server.GrpcServerFactoryAutoConfiguration
 org.springframework.grpc.autoconfigure.server.GrpcServerAutoConfiguration
 org.springframework.grpc.autoconfigure.server.health.GrpcServerHealthAutoConfiguration

spring-grpc-spring-boot-autoconfigure/src/test/java/org/springframework/grpc/autoconfigure/client/GrpcClientObservationAutoConfigurationTest.java

@@ -0,0 +1,89 @@
+/*
+ * Copyright 2024-2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.grpc.autoconfigure.client;
+
+import io.micrometer.core.instrument.binder.grpc.ObservationGrpcClientInterceptor;
+import io.micrometer.observation.ObservationRegistry;
+import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
+import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.test.context.FilteredClassLoader;
+import org.springframework.boot.test.context.runner.ApplicationContextRunner;
+import org.springframework.grpc.client.GlobalClientInterceptor;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for the {@link GrpcClientObservationAutoConfiguration}.
+ */
+class GrpcClientObservationAutoConfigurationTests {
+
+	private final ApplicationContextRunner baseContextRunner = new ApplicationContextRunner()
+		.withConfiguration(AutoConfigurations.of(GrpcClientObservationAutoConfiguration.class));
+
+	private ApplicationContextRunner validContextRunner() {
+		return new ApplicationContextRunner()
+			.withConfiguration(AutoConfigurations.of(GrpcClientObservationAutoConfiguration.class))
+			.withBean("observationRegistry", ObservationRegistry.class, Mockito::mock);
+	}
+
+	@Test
+	void whenObservationRegistryNotOnClasspathAutoConfigSkipped() {
+		this.validContextRunner()
+			.withClassLoader(new FilteredClassLoader(ObservationRegistry.class))
+			.run((context) -> assertThat(context).doesNotHaveBean(GrpcClientObservationAutoConfiguration.class));
+	}
+
+	@Test
+	void whenObservationGrpcClientInterceptorNotOnClasspathAutoConfigSkipped() {
+		this.validContextRunner()
+			.withClassLoader(new FilteredClassLoader(ObservationGrpcClientInterceptor.class))
+			.run((context) -> assertThat(context).doesNotHaveBean(GrpcClientObservationAutoConfiguration.class));
+	}
+
+	@Test
+	void whenObservationRegistryNotProvidedThenAutoConfigSkipped() {
+		this.baseContextRunner
+			.run(context -> assertThat(context).doesNotHaveBean(GrpcClientObservationAutoConfiguration.class));
+	}
+
+	@Test
+	void whenObservationPropertyEnabledThenAutoConfigNotSkipped() {
+		this.validContextRunner()
+			.withPropertyValues("spring.grpc.client.observation.enabled=true")
+			.run(context -> assertThat(context).hasSingleBean(GrpcClientObservationAutoConfiguration.class));
+	}
+
+	@Test
+	void whenObservationPropertyDisabledThenAutoConfigIsSkipped() {
+		this.validContextRunner()
+			.withPropertyValues("spring.grpc.client.observation.enabled=false")
+			.run(context -> assertThat(context).doesNotHaveBean(GrpcClientObservationAutoConfiguration.class));
+	}
+
+	@Test
+	void whenAllConditionsAreMetThenInterceptorConfiguredAsExpected() {
+		this.validContextRunner().run((context) -> {
+			assertThat(context).hasSingleBean(ObservationGrpcClientInterceptor.class);
+			assertThat(context.getBeansWithAnnotation(GlobalClientInterceptor.class)).hasEntrySatisfying(
+					"observationGrpcClientInterceptor",
+					bean -> assertThat(bean.getClass().isAssignableFrom(ObservationGrpcClientInterceptor.class))
+						.isTrue());
+		});
+	}
+
+}