Add prometheus to actuator-webmvc sample

Closes gh-86

actuator-webmvc/build.gradle

@@ -9,7 +9,8 @@ dependencies {
 	implementation(platform(org.springframework.boot.gradle.plugin.SpringBootPlugin.BOM_COORDINATES))
 	implementation("org.springframework.boot:spring-boot-starter-actuator")
 	implementation("org.springframework.boot:spring-boot-starter-web")
-	implementation("io.micrometer:micrometer-registry-prometheus")
+
+	runtimeOnly("io.micrometer:micrometer-registry-prometheus")
 
 	testImplementation("org.springframework.boot:spring-boot-starter-test")
 

actuator-webmvc/src/aotTest/java/com/example/actuator/webmvc/ActuatorWebMvcApplicationAotTests.java

@@ -66,11 +66,14 @@ class ActuatorWebMvcApplicationAotTests {
 	}
 
 	@Test
-	void shouldHavePrometheusMetrics(WebTestClient client) {
+	void prometheusWorks(WebTestClient client) {
 		client.get().uri("/actuator/prometheus").exchange().expectStatus().isOk().expectBody()
 				.consumeWith((result) -> assertThat(new String(result.getResponseBodyContent()))
-						.contains("jvm_classes_loaded_classes "));
-
+						// Check custom timer
+						.contains("custom_timer_seconds_max 5.0").contains("custom_timer_seconds_count 1.0")
+						.contains("custom_timer_seconds_sum 5.0")
+						// Check JVM metric
+						.contains("# TYPE jvm_threads_peak_threads gauge"));
 	}
 
 }

actuator-webmvc/src/main/java/com/example/actuator/webmvc/RegisterCustomTimer.java

@@ -0,0 +1,24 @@
+package com.example.actuator.webmvc;
+
+import java.time.Duration;
+
+import io.micrometer.core.instrument.MeterRegistry;
+
+import org.springframework.boot.CommandLineRunner;
+import org.springframework.stereotype.Component;
+
+@Component
+class RegisterCustomTimer implements CommandLineRunner {
+
+	private final MeterRegistry meterRegistry;
+
+	RegisterCustomTimer(MeterRegistry meterRegistry) {
+		this.meterRegistry = meterRegistry;
+	}
+
+	@Override
+	public void run(String... args) {
+		this.meterRegistry.timer("custom.timer").record(Duration.ofSeconds(5));
+	}
+
+}