Adds eureka support to micrometer example

build-bin/test

@@ -15,7 +15,7 @@ build-bin/docker/docker_build ${docker_image} ${VERSION}
 docker_compose_file=build-bin/docker-compose.test.yml
 
 case ${VERSION} in
-  armeria|*sleuth* )
+  armeria|*sleuth*|*micrometer* )
     docker_compose_file=build-bin/docker-compose-eureka.test.yml
     ;;
   armeria-kafka )

webflux6-micrometer/pom.xml

@@ -19,34 +19,10 @@
     <jre.version>21</jre.version>
     <maven.compiler.release>17</maven.compiler.release>
 
-    <spring-boot.version>3.3.0-RC1</spring-boot.version>
+    <spring-boot.version>3.3.0</spring-boot.version>
     <micrometer.version>1.3.0</micrometer.version>
   </properties>
 
-  <!-- Temporary until Spring boot 3.3.0 -->
-  <pluginRepositories>
-    <pluginRepository>
-      <id>repository.spring.milestone</id>
-      <name>Spring Milestone Repository</name>
-      <url>https://repo.spring.io/milestone</url>
-      <snapshots>
-        <enabled>false</enabled>
-      </snapshots>
-    </pluginRepository>
-  </pluginRepositories>
-
-  <!-- Temporary until Spring boot 3.3.0 -->
-  <repositories>
-    <repository>
-      <id>repository.spring.milestone</id>
-      <name>Spring Milestone Repository</name>
-      <url>https://repo.spring.io/milestone</url>
-      <snapshots>
-        <enabled>false</enabled>
-      </snapshots>
-    </repository>
-  </repositories>
-
   <dependencyManagement>
     <dependencies>
       <dependency>
@@ -71,6 +47,23 @@
       <artifactId>spring-boot-starter-actuator</artifactId>
       <version>${spring-boot.version}</version>
     </dependency>
+    <dependency>
+      <groupId>org.springframework.cloud</groupId>
+      <artifactId>spring-cloud-starter-loadbalancer</artifactId>
+      <version>4.1.2</version>
+    </dependency>
+    <dependency>
+      <groupId>org.springframework.cloud</groupId>
+      <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
+      <version>4.1.1</version>
+      <exclusions>
+        <!-- dodge spring-jcl conflict error -->
+        <exclusion>
+          <groupId>commons-logging</groupId>
+          <artifactId>commons-logging</artifactId>
+        </exclusion>
+      </exclusions>
+    </dependency>
 
     <!-- micrometer-tracing-bridge-brave configures instrumentation including what's in Brave and their own. -->
     <dependency>

webflux6-micrometer/src/main/java/brave/example/Backend.java

@@ -1,9 +1,13 @@
 package brave.example;
 
 import java.time.LocalDate;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.Map;
 import java.util.Optional;
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.builder.SpringApplicationBuilder;
 import org.springframework.context.annotation.Import;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.RequestHeader;
@@ -12,7 +16,10 @@
 
 @EnableAutoConfiguration
 @RestController
-@Import(CustomObservationConfiguration.class)
+@Import(value = {
+    CustomObservationConfiguration.class,
+    ZipkinDiscoveryConfiguration.class
+})
 public class Backend {
 
   @GetMapping("/api")
@@ -24,9 +31,8 @@ public Mono<String> printDate(@RequestHeader("user_name") Optional<String> usern
   }
 
   public static void main(String[] args) {
-    SpringApplication.run(Backend.class,
-        "--spring.application.name=backend",
-        "--server.port=9000"
-    );
+    new SpringApplicationBuilder(Backend.class)
+        .properties(ZipkinDiscoveryConfiguration.discoveryProperties())
+        .run("--spring.application.name=backend", "--server.port=9000");
   }
 }

webflux6-micrometer/src/main/java/brave/example/CustomObservationConfiguration.java

@@ -1,6 +1,5 @@
 package brave.example;
 
-import brave.http.HttpTracing;
 import io.micrometer.observation.ObservationPredicate;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -21,7 +20,7 @@ public class CustomObservationConfiguration {
    * spring.sleuth.web.additional-skip-pattern=/health
    * </pre>
    *
-   * <p>Brave uses {@link HttpTracing#serverRequestSampler()} for server request sampling policy.
+   * <p>Brave uses {@code HttpTracing#serverRequestSampler()} for server request sampling policy.
    * Micrometer tracing bridges to Brave's core API, so it doesn't see or use the HTTP, Messaging or
    * RPC policies. Instead, it relies on its own type, {@link ObservationPredicate}, which applies
    * both to metrics and tracing.

webflux6-micrometer/src/main/java/brave/example/Frontend.java

@@ -2,8 +2,8 @@
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Value;
-import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.builder.SpringApplicationBuilder;
 import org.springframework.context.annotation.Import;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.RestController;
@@ -12,7 +12,10 @@
 
 @EnableAutoConfiguration
 @RestController
-@Import(CustomObservationConfiguration.class)
+@Import(value = {
+    CustomObservationConfiguration.class,
+    ZipkinDiscoveryConfiguration.class
+})
 public class Frontend {
   final WebClient webClient;
 
@@ -26,9 +29,10 @@ public class Frontend {
   }
 
   public static void main(String[] args) {
-    SpringApplication.run(Frontend.class,
-        "--spring.application.name=frontend",
-        "--server.port=8081"
-    );
+    new SpringApplicationBuilder(Frontend.class)
+        .properties(ZipkinDiscoveryConfiguration.discoveryProperties())
+        .run("--spring.application.name=frontend",
+            "--server.port=8081"
+        );
   }
 }

webflux6-micrometer/src/main/java/brave/example/ZipkinDiscoveryConfiguration.java

@@ -0,0 +1,67 @@
+package brave.example;
+
+import java.net.URI;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
+import org.springframework.cloud.client.ServiceInstance;
+import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import zipkin2.reporter.HttpEndpointSupplier;
+import zipkin2.reporter.HttpEndpointSuppliers;
+
+@Configuration(proxyBeanMethods = false)
+@ConditionalOnProperty("EUREKA_SERVICE_URL")
+public class ZipkinDiscoveryConfiguration {
+
+  /**
+   * It is very difficult to stop loadbalancer or discovery from initializing when starters are on
+   * the classpath. This is a workaround to disable it when EUREKA_SERVICE_URL is not set.
+   */
+  static Map<String, Object> discoveryProperties() {
+    Map<String, Object> properties = new LinkedHashMap<>();
+    String eurekaServiceUrl = System.getenv("EUREKA_SERVICE_URL");
+    boolean eurekaEnabled = eurekaServiceUrl != null && !eurekaServiceUrl.isEmpty();
+    if (eurekaEnabled) {
+      properties.put("eureka.client.serviceUrl.defaultZone", eurekaServiceUrl);
+    }
+    properties.put("spring.cloud.loadbalancer.enabled", eurekaEnabled);
+    properties.put("spring.cloud.discovery.enabled", eurekaEnabled);
+    return properties;
+  }
+
+  @Bean HttpEndpointSupplier.Factory loadbalancerEndpoints(LoadBalancerClient loadBalancerClient) {
+    LoadBalancerHttpEndpointSupplier.Factory httpEndpointSupplierFactory =
+        new LoadBalancerHttpEndpointSupplier.Factory(loadBalancerClient);
+    // don't ask more than 30 seconds (just to show)
+    return HttpEndpointSuppliers.newRateLimitedFactory(httpEndpointSupplierFactory, 30);
+  }
+
+  record LoadBalancerHttpEndpointSupplier(LoadBalancerClient loadBalancerClient, URI virtualURL)
+      implements HttpEndpointSupplier {
+    record Factory(LoadBalancerClient loadBalancerClient) implements HttpEndpointSupplier.Factory {
+
+      @Override public HttpEndpointSupplier create(String endpoint) {
+        return new LoadBalancerHttpEndpointSupplier(loadBalancerClient, URI.create(endpoint));
+      }
+    }
+
+    @Override public String get() {
+      // At least spring-cloud-netflix wants the actual hostname as a lookup value
+      ServiceInstance instance = loadBalancerClient.choose(virtualURL.getHost());
+      if (instance != null) {
+        return instance.getUri() + virtualURL.getPath();
+      }
+      throw new IllegalArgumentException(
+          virtualURL.getHost() + " is not an instance registered in Eureka");
+    }
+
+    @Override public void close() {
+    }
+
+    @Override public String toString() {
+      return "LoadBalancer{" + virtualURL + "}";
+    }
+  }
+}

webflux6-micrometer/src/main/resources/application.yaml

@@ -34,6 +34,10 @@ management:
     tracing:
       # Note: There is no property to bind ${brave.localServiceName:${spring.application.name}}
       endpoint: ${zipkin.baseUrl:http://127.0.0.1:9411}/api/v2/spans
+spring:
+  cloud:
+    compatibilityVerifier:
+      enabled: false
 
 logging:
   level: