Initial commit

Author: monodot

.gitignore

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+HELP.md
+target/
+!.mvn/wrapper/maven-wrapper.jar
+!**/src/main/**/target/
+!**/src/test/**/target/
+
+### STS ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+
+### IntelliJ IDEA ###
+.idea
+*.iws
+*.iml
+*.ipr
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+build/
+!**/src/main/**/build/
+!**/src/test/**/build/
+
+### VS Code ###
+.vscode/

README.md

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+# spring-boot-with-metrics
+
+This demo app shows how a Spring Boot application can expose a Prometheus metrics endpoint for scraping.
+
+🚼 The app was initially created with [Spring Initializr][init] and then by following the [RESTful service tutorial on spring.io][rest-tutorial].
+
+To run the app:
+
+    mvn clean spring-boot:run
+    
+This will expose Prometheus metrics at `/actuator/prometheus`. This is a simple `key value` listing of metrics. You can check them out using `curl`, for example:
+
+    $ curl http://localhost:8080/actuator/prometheus
+    # HELP process_uptime_seconds The uptime of the Java virtual machine
+    # TYPE process_uptime_seconds gauge
+    process_uptime_seconds 10.284
+    # HELP jvm_threads_states_threads The current number of threads having NEW state
+    # TYPE jvm_threads_states_threads gauge
+    jvm_threads_states_threads{state="runnable",} 9.0
+    jvm_threads_states_threads{state="blocked",} 0.0
+    jvm_threads_states_threads{state="waiting",} 11.0
+    ...
+    # TYPE tomcat_sessions_alive_max_seconds gauge
+    tomcat_sessions_alive_max_seconds 0.0
+    ...    
+
+Once you make a request to the service at <http://localhost:8080/greeting>, you will also see a new metric exposed, `greeting_time_seconds` exposed, which shows the execution time of the `greeting` method:
+
+    # HELP greeting_time_seconds Time taken to return greeting
+    # TYPE greeting_time_seconds summary
+    greeting_time_seconds{class="com.tutorialworks.demos.springbootwithmetrics.GreetingController",exception="none",met
+    hod="greeting",quantile="0.9",} 0.02097152
+    greeting_time_seconds_count{class="com.tutorialworks.demos.springbootwithmetrics.GreetingController",exception="non
+    e",method="greeting",} 1.0
+    greeting_time_seconds_sum{class="com.tutorialworks.demos.springbootwithmetrics.GreetingController",exception="none"
+    ,method="greeting",} 0.021689345
+    # HELP greeting_time_seconds_max Time taken to return greeting
+    # TYPE greeting_time_seconds_max gauge
+    greeting_time_seconds_max{class="com.tutorialworks.demos.springbootwithmetrics.GreetingController",exception="none",method="greeting",} 0.021689345
+
+
+From the [Micrometer docs][timerdocs]:
+
+> All implementations of _Timer_ report at least the total time and count of events as separate time series.
+
+Now we need to get these metrics into Prometheus.
+
+In another terminal, use Podman to start an ephemeral Prometheus in a container, and use the `host` networking option, which will allow the container to access the Spring Boot app on `localhost`:
+
+    podman run --net=host \
+        -v prometheus.yml:/etc/prometheus/prometheus.yml \
+        prom/prometheus
+        
+Check the Prometheus console at <http://localhost:9090>.
+
+- Go to _Targets_, you should see the Spring Boot app being scraped successfully.
+
+- On the _Graph_ page, you should be able to type in a metric from the application (e.g. `tomcat_sessions_active_current_sessions`, or `greeting_time_seconds`) and see the raw data, or plot a graph
+
+## Troubleshooting
+
+Inside the Prometheus container, you can check that you can access the Spring Boot metrics:
+
+    $ podman exec -it <container-name> sh
+    $$ wget -S -O - http://localhost:8080/actuator/prometheus
+
+
+[rest-tutorial]: https://spring.io/guides/gs/rest-service/
+[init]: https://start.spring.io
+[timerdocs]: https://micrometer.io/docs/concepts#_timers

pom.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<parent>
+		<groupId>org.springframework.boot</groupId>
+		<artifactId>spring-boot-starter-parent</artifactId>
+		<version>2.4.1</version>
+		<relativePath/> <!-- lookup parent from repository -->
+	</parent>
+	<groupId>com.tutorialworks.demos</groupId>
+	<artifactId>spring-boot-with-metrics</artifactId>
+	<version>0.0.1-SNAPSHOT</version>
+	<name>spring-boot-with-metrics</name>
+	<description>Spring Boot with Metrics Demo</description>
+
+	<properties>
+		<java.version>11</java.version>
+	</properties>
+
+	<dependencies>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-web</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-actuator</artifactId>
+		</dependency>
+
+		<!-- Contains aspectj - required by TimedAspect -->
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-aop</artifactId>
+		</dependency>
+
+		<dependency>
+			<groupId>io.micrometer</groupId>
+			<artifactId>micrometer-registry-prometheus</artifactId>
+			<scope>runtime</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-test</artifactId>
+			<scope>test</scope>
+		</dependency>
+	</dependencies>
+
+	<build>
+		<plugins>
+			<plugin>
+				<groupId>org.springframework.boot</groupId>
+				<artifactId>spring-boot-maven-plugin</artifactId>
+			</plugin>
+		</plugins>
+	</build>
+
+</project>

prometheus.yml

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+# Sample Prometheus config
+# This assumes that your Prometheus instance can access this application on localhost:8080
+
+global:
+  scrape_interval:     15s # Set the scrape interval to every 15 seconds. Default is every 1 minute.
+  evaluation_interval: 15s # Evaluate rules every 15 seconds. The default is every 1 minute.
+  # scrape_timeout is set to the global default (10s).
+
+scrape_configs:
+  - job_name: 'spring boot scrape'
+    metrics_path: '/actuator/prometheus'
+    scrape_interval: 5s
+    static_configs:
+      - targets: ['localhost:8080']

src/main/java/com/tutorialworks/demos/springbootwithmetrics/Greeting.java

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+package com.tutorialworks.demos.springbootwithmetrics;
+
+public class Greeting {
+
+    private final long id;
+    private final String content;
+
+    public Greeting(long id, String content) {
+        this.id = id;
+        this.content = content;
+    }
+
+    public long getId() {
+        return id;
+    }
+
+    public String getContent() {
+        return content;
+    }
+}

src/main/java/com/tutorialworks/demos/springbootwithmetrics/GreetingController.java

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+package com.tutorialworks.demos.springbootwithmetrics;
+
+import io.micrometer.core.annotation.Timed;
+import io.micrometer.core.instrument.MeterRegistry;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestParam;
+import org.springframework.web.bind.annotation.RestController;
+
+import java.util.concurrent.atomic.AtomicLong;
+
+@RestController
+public class GreetingController {
+
+    private static final String template = "Hello, %s!";
+    private final AtomicLong counter = new AtomicLong();
+
+    private final MeterRegistry registry;
+
+    /**
+     * We inject the MeterRegistry into this class
+     */
+    public GreetingController(MeterRegistry registry) {
+        this.registry = registry;
+    }
+
+    /**
+     * The @Timed annotation adds timing support, so we can see how long
+     * it takes to execute in Prometheus
+     * percentiles
+     */
+    @GetMapping("/greeting")
+    @Timed(value = "greeting.time", description = "Time taken to return greeting",
+            percentiles = {0.5, 0.90})
+    public Greeting greeting(@RequestParam(value = "name", defaultValue = "World") String name) {
+        return new Greeting(counter.incrementAndGet(), String.format(template, name));
+    }
+
+}

src/main/java/com/tutorialworks/demos/springbootwithmetrics/SpringBootWithMetricsApplication.java

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+package com.tutorialworks.demos.springbootwithmetrics;
+
+import io.micrometer.core.aop.TimedAspect;
+import io.micrometer.core.instrument.MeterRegistry;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.context.annotation.Bean;
+
+@SpringBootApplication
+public class SpringBootWithMetricsApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(SpringBootWithMetricsApplication.class, args);
+	}
+
+	/**
+	 * This is required so that we can use the @Timed annotation
+	 * on methods that we want to time.
+	 * See: https://micrometer.io/docs/concepts#_the_timed_annotation
+	 */
+	@Bean
+	public TimedAspect timedAspect(MeterRegistry registry) {
+		return new TimedAspect(registry);
+	}
+
+}

src/main/resources/application.properties

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+management.endpoints.web.exposure.include=health,info,prometheus

src/test/java/com/tutorialworks/demos/springbootwithmetrics/SpringBootWithMetricsApplicationTests.java

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+package com.tutorialworks.demos.springbootwithmetrics;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.boot.test.context.SpringBootTest;
+
+@SpringBootTest
+class SpringBootWithMetricsApplicationTests {
+
+	@Test
+	void contextLoads() {
+	}
+
+}