Add Kotlin observation interceptor with order

Fixes gh-221

Author: dsyer

spring-grpc-spring-boot-autoconfigure/src/main/java/org/springframework/grpc/autoconfigure/server/GrpcServerObservationAutoConfiguration.java

@@ -20,9 +20,12 @@
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.core.annotation.Order;
 import org.springframework.grpc.server.GlobalServerInterceptor;
 
 import io.micrometer.core.instrument.binder.grpc.ObservationGrpcServerInterceptor;
+import io.micrometer.core.instrument.kotlin.ObservationCoroutineContextServerInterceptor;
 import io.micrometer.observation.ObservationRegistry;
 
 @AutoConfiguration(
@@ -34,9 +37,24 @@
 public class GrpcServerObservationAutoConfiguration {
 
 	@Bean
+	@Order(0)
 	@GlobalServerInterceptor
 	ObservationGrpcServerInterceptor observationGrpcServerInterceptor(ObservationRegistry observationRegistry) {
 		return new ObservationGrpcServerInterceptor(observationRegistry);
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	@ConditionalOnClass(name = "io.grpc.kotlin.AbstractCoroutineStub")
+	static class GrpcServerCoroutineStubConfiguration {
+
+		@Bean
+		@Order(10)
+		@GlobalServerInterceptor
+		ObservationCoroutineContextServerInterceptor observationCoroutineGrpcServerInterceptor(
+				ObservationRegistry observationRegistry) {
+			return new ObservationCoroutineContextServerInterceptor(observationRegistry);
+		}
+
+	}
+
 }

spring-grpc-spring-boot-autoconfigure/src/test/java/org/springframework/grpc/autoconfigure/server/GrpcServerObservationAutoConfigurationTests.java

@@ -18,15 +18,19 @@
 
 import static org.assertj.core.api.Assertions.assertThat;
 
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
 import org.assertj.core.api.Condition;
 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.server.GlobalServerInterceptor;
 
+import io.grpc.ServerInterceptor;
 import io.micrometer.core.instrument.binder.grpc.ObservationGrpcServerInterceptor;
 import io.micrometer.observation.ObservationRegistry;
 
@@ -102,8 +106,13 @@ void whenServerEnabledPropertySetTrueThenAutoConfigurationIsNotSkipped() {
 	void whenAllConditionsAreMetThenInterceptorConfiguredAsExpected() {
 		this.validContextRunner()
 			.run((context) -> assertThat(context).hasSingleBean(ObservationGrpcServerInterceptor.class)
-				.has(new Condition<>(beans -> beans.getBeansWithAnnotation(GlobalServerInterceptor.class).size() == 1,
-						"One global interceptor expected")));
+				.has(new Condition<>(beans -> {
+					Map<String, Object> annotated = beans.getBeansWithAnnotation(GlobalServerInterceptor.class);
+					List<ServerInterceptor> interceptors = beans.getBeanProvider(ServerInterceptor.class)
+						.orderedStream()
+						.collect(Collectors.toList());
+					return annotated.size() == 2 && interceptors.get(0) instanceof ObservationGrpcServerInterceptor;
+				}, "Two global interceptors expected")));
 	}
 
 }