#1411: Add more practical example for module micrometer-quickstart

micrometer-quickstart/src/main/java/org/acme/micrometer/ExampleResource.java

@@ -17,7 +17,7 @@ public class ExampleResource {
 
     private final MeterRegistry registry;
 
-    LinkedList<Long> list = new LinkedList<>();
+    private final LinkedList<Long> list = new LinkedList<>();
 
     // Update the constructor to create the gauge
     ExampleResource(MeterRegistry registry) {

micrometer-quickstart/src/main/java/org/acme/micrometer/TemperatureResource.java

@@ -0,0 +1,121 @@
+package org.acme.micrometer;
+
+import java.util.LinkedList;
+
+import jakarta.ws.rs.GET;
+import jakarta.ws.rs.Path;
+import jakarta.ws.rs.Produces;
+import jakarta.ws.rs.PathParam;
+
+import io.micrometer.core.instrument.MeterRegistry;
+import io.micrometer.core.instrument.Tags;
+import io.micrometer.core.instrument.Timer;
+import io.micrometer.core.instrument.DistributionSummary;
+
+/**
+ * REST API for monitoring and recording temperature readings.
+ */
+@Path("/temperature")
+@Produces("text/plain")
+public class TemperatureResource {
+
+	private final MeterRegistry registry;
+	private LinkedList<Double> temperatures = new LinkedList<>();
+
+	DistributionSummary temperatureSummary;
+
+	/**
+	 * Constructs a TemperatureResource.
+	 * Initializes the monitoring tools for temperatures.
+	 *
+	 * @param registry MeterRegistry for recording metrics.
+	 */
+	public TemperatureResource(MeterRegistry registry) {
+		this.registry = registry;
+		// Summary to record temperature readings and their distribution.
+		temperatureSummary = registry.summary("temperature.readings", Tags.of("unit", "celsius"));
+		// Gauge to monitor the size of the temperature list in real-time.
+		registry.gaugeCollectionSize("temperature.list.size", Tags.empty(), temperatures);
+	}
+
+	/**
+	 * Adds a temperature reading to the recorded list and updates the summary metric.
+	 *
+	 * @param temp The temperature to add.
+	 * @return A message confirming the addition of the temperature.
+	 */
+	@GET
+	@Path("/add/{temp}")
+	public String addTemperature(@PathParam("temp") double temp) {
+		temperatures.add(temp);
+		temperatureSummary.record(temp);
+		return "Temperature added: " + temp;
+	}
+
+	/**
+	 * Calculates the average of all recorded temperatures.
+	 * Uses a timer to measure the time taken to perform this calculation.
+	 *
+	 * @return The average temperature or a message if no temperatures are recorded.
+	 */
+	@GET
+	@Path("/average")
+	public String calculateAverage() {
+		Timer timer = registry.timer("temperature.calculation.average");
+		return timer.record(() -> {
+			if (temperatures.isEmpty()) {
+				return "No temperatures recorded.";
+			}
+			double sum = 0;
+			for (Double t : temperatures) {
+				sum += t;
+			}
+			double average = sum / temperatures.size();
+			return "Average temperature: " + average + " Celsius";
+		});
+	}
+
+	/**
+	 * Finds the maximum temperature from the recorded list.
+	 * Measurement is timed for performance analysis.
+	 *
+	 * @return The maximum temperature or a message if no temperatures are recorded.
+	 */
+	@GET
+	@Path("/max")
+	public String findMaxTemperature() {
+		Timer timer = registry.timer("temperature.calculation.max");
+		return timer.record(() -> {
+			return temperatures.stream()
+					.max(Double::compare)
+					.map(maxTemp -> "Maximum temperature: " + maxTemp + " Celsius")
+					.orElse("No temperatures recorded.");
+		});
+	}
+
+	/**
+	 * Finds the minimum temperature from the recorded list.
+	 * Measurement is timed for performance analysis.
+	 *
+	 * @return The minimum temperature or a message if no temperatures are recorded.
+	 */
+	@GET
+	@Path("/min")
+	public String findMinTemperature() {
+		Timer timer = registry.timer("temperature.calculation.min");
+		return timer.record(() -> {
+			return temperatures.stream()
+					.min(Double::compare)
+					.map(minTemp -> "Minimum temperature: " + minTemp + " Celsius")
+					.orElse("No temperatures recorded.");
+		});
+	}
+
+	// New endpoint to reset the temperatures list
+	@GET
+	@Path("/reset")
+	public String resetTemperatures() {
+		temperatures.clear();
+		return "Temperatures reset successfully.";
+	}
+}

micrometer-quickstart/src/test/java/org/acme/micrometer/TemperatureResourceTest.java

@@ -0,0 +1,85 @@
+package org.acme.micrometer;
+
+import static io.restassured.RestAssured.get;
+import static io.restassured.RestAssured.when;
+import static org.hamcrest.CoreMatchers.containsString;
+
+import org.junit.jupiter.api.Test;
+
+import io.quarkus.test.junit.QuarkusTest;
+import io.restassured.http.Header;
+
+/**
+ * Test class for TemperatureResource using REST-assured.
+ */
+@QuarkusTest
+public class TemperatureResourceTest {
+
+	@BeforeEach
+	void resetTemperatures() {
+		get("/temperature/reset").then().assertThat().statusCode(200);
+	}
+
+	@Test
+	void testAddTemperature() {
+		when().get("/temperature/add/20.5").then().statusCode(200)
+				.body(containsString("Temperature added: 20.5"));
+		when().get("/temperature/add/22.3").then().statusCode(200)
+				.body(containsString("Temperature added: 22.3"));
+	}
+
+	@Test
+	void testAverageTemperature() {
+		// Add temperatures first
+		get("/temperature/add/20.5");
+		get("/temperature/add/22.3");
+		get("/temperature/add/25.1");
+
+		// Check the average calculation
+		when().get("/temperature/average").then().statusCode(200)
+				.body(containsString("Average temperature: 22.633333333333333 Celsius"));
+	}
+
+	@Test
+	void testMaxTemperature() {
+		// Add temperatures first
+		get("/temperature/add/20.5");
+		get("/temperature/add/22.3");
+		get("/temperature/add/25.1");
+
+		// Check the maximum temperature calculation
+		when().get("/temperature/max").then().statusCode(200)
+				.body(containsString("Maximum temperature: 25.1 Celsius"));
+	}
+
+	@Test
+	void testMinTemperature() {
+		// Add temperatures first
+		get("/temperature/add/20.5");
+		get("/temperature/add/22.3");
+		get("/temperature/add/25.1");
+
+		// Check the minimum temperature calculation
+		when().get("/temperature/min").then().statusCode(200)
+				.body(containsString("Minimum temperature: 20.5 Celsius"));
+	}
+
+	@Test
+	void testTemperatureMetrics() {
+		// Trigger endpoints to populate metrics
+		get("/temperature/add/20.5");
+		get("/temperature/add/22.3");
+		get("/temperature/add/25.1");
+		get("/temperature/average");
+		get("/temperature/max");
+		get("/temperature/min");
+
+		// Check metrics for recorded operations
+		when().get("/q/metrics").then().statusCode(200)
+				.body(containsString("temperature_readings_sum"))
+				.body(containsString("temperature_readings_count 3.0"))
+				.body(containsString("temperature_calculation_average_seconds_count 1.0"))
+				.body(containsString("temperature_calculation_max_seconds_count 1.0"))
+				.body(containsString("temperature_calculation_min_seconds_count 1.0"));
+	}
+}