Merge pull request 'Add a REST API to access the current temperature' (#13) from rest into master

Reviewed-on: #13

README.md

@@ -40,8 +40,8 @@ The container `application` can be easily modified with the following environmen
 | TEMPERATURE_LOCATION         | true     | \<latitude>, \<longitude>                           | 49.9, 2.3 ([Amiens, France](https://fr.wikipedia.org/wiki/Amiens)) | The coordinates where to get the temperatures from            |
 
 ## Expectation
-The `application` container shall print the current temperature at the selected place in
-Fahrenheit every minute.
+The `application` container shall print the current temperature at the selected place in Fahrenheit every minute.  
+You can also access this value with the REST api at the `http://localhost:8080/temperature` endpoint.  
 
 ## References
 The project use the [Open-Meteo API](https://open-meteo.com/) to fetch the current temperature at the

build.gradle.kts

@@ -27,9 +27,9 @@ dependencies {
     implementation("io.quarkus:quarkus-kafka-client")
     implementation("io.quarkus:quarkus-kafka-streams")
     implementation("io.quarkus:quarkus-messaging-kafka")
+    implementation("io.quarkus:quarkus-rest")
     implementation("com.squareup.okhttp3:okhttp:4.12.0")
     implementation("com.google.code.gson:gson:2.8.9")
-
 }
 
 group = "fr.faraphel"

docker-compose.yaml

@@ -32,9 +32,17 @@ services:
     build:
       context: .
       dockerfile: ./src/main/docker/Dockerfile.${QUARKUS_MODE:-jvm}
+    ports:
+      - "8080:8080"
     environment:
       KAFKA_BOOTSTRAP_SERVERS: kafka:9092
       TEMPERATURE_LOCATION: 49.9, 2.3
+    healthcheck:
+      test: curl --fail http://localhost:8080/ping
+      start_period: 10s
+      timeout: 5s
+      interval: 60s
+      retries: 3
     networks:
       - kafka
     depends_on:

src/main/kotlin/fr/faraphel/m1_pe_kafka/Main.kt

@@ -2,13 +2,17 @@ package fr.faraphel.m1_pe_kafka
 
 import fr.faraphel.m1_pe_kafka.error.MissingEnvironmentException
 import fr.faraphel.m1_pe_kafka.kafka.AdminUtils
-import fr.faraphel.m1_pe_kafka.kafka.PrintConsumer
+import fr.faraphel.m1_pe_kafka.kafka.Consumer
 import fr.faraphel.m1_pe_kafka.kafka.Converter
 import fr.faraphel.m1_pe_kafka.kafka.TemperatureProducer
+import fr.faraphel.m1_pe_kafka.rest.TemperatureEndpoint
 import fr.faraphel.m1_pe_kafka.utils.celsius
 import io.quarkus.runtime.Quarkus
 import io.quarkus.runtime.QuarkusApplication
 import io.quarkus.runtime.annotations.QuarkusMain
+import java.time.Instant
+import java.time.ZoneId
+import java.time.format.DateTimeFormatter
 
 
 /**
@@ -24,6 +28,11 @@ class Main : QuarkusApplication {
      * @throws MissingEnvironmentException a required environment variable from the configuration is missing
      */
     override fun run(vararg args: String?): Int {
+        // create a time formatter
+        val timeFormatter = DateTimeFormatter
+            .ofPattern("yyyy-MM-dd HH:mm:ss.SSS")
+            .withZone(ZoneId.systemDefault())
+
         // get the kafka server address
         val kafkaServer = System.getenv("KAFKA_BOOTSTRAP_SERVERS")
             ?: throw MissingEnvironmentException("KAFKA_BOOTSTRAP_SERVERS")
@@ -62,10 +71,17 @@ class Main : QuarkusApplication {
         ) { temperature -> temperature.celsius.asFahrenheit }
 
         // create a consumer that will print the received values in the Fahrenheit topic
-        val consumer = PrintConsumer(
+        val consumer = Consumer(
             server=kafkaServer,
             topic=topicTemperatureFahrenheit
-        )
+        ) { message ->
+            // format the time of the message to a proper string
+            val time = timeFormatter.format(Instant.ofEpochMilli(message.timestamp()))
+            // print the value
+            println("[${time}] ${message.value()}°F")
+            // update the value for the API
+            TemperatureEndpoint.setTemperature(message.value())
+        }
 
         // run all the clients
         producer.start()

src/main/kotlin/fr/faraphel/m1_pe_kafka/kafka/Consumer.kt

@@ -4,37 +4,27 @@ package fr.faraphel.m1_pe_kafka.kafka
 import org.apache.kafka.clients.consumer.*
 import org.apache.kafka.common.serialization.DoubleDeserializer
 import org.apache.kafka.common.serialization.StringDeserializer
-import java.time.DateTimeException
 
 import java.time.Duration
-import java.time.Instant
-import java.time.ZoneId
-import java.time.format.DateTimeFormatter
 import java.util.Collections
 import java.util.Properties
-import kotlin.time.Duration.Companion.milliseconds
 import kotlin.time.Duration.Companion.seconds
 import kotlin.time.toJavaDuration
 
 
 /**
- * A basic consumer that print everything in the selected topic.
+ * A basic consumer that call a function on all received messages
  * @param server the kafka server address
  * @param topic the topic to get the records from
  * @param identifier the kafka identifier for the configuration
+ * @param callback the function to call on all messages
  */
-class PrintConsumer(
+class Consumer(
     private val server: String,
     private val identifier: String = "consumer",
     private val topic: String,
+    private val callback: (ConsumerRecord<String, Double>) -> Unit,
 ) : Thread() {
-    companion object {
-        // create a formatter to convert the timestamp to a string
-        private val timeFormatter = DateTimeFormatter
-            .ofPattern("yyyy-MM-dd HH:mm:ss.SSS")
-            .withZone(ZoneId.systemDefault())
-    }
-
     private val properties: Properties = Properties().apply {
         // identifier
         this[ConsumerConfig.GROUP_ID_CONFIG] = identifier
@@ -59,12 +49,7 @@ class PrintConsumer(
         val messages: ConsumerRecords<String, Double> = this.consumer.poll(timeout)
 
         // print them with their timestamp and content
-        messages.forEach { message ->
-            // format the time of the message to a proper string
-            val time = timeFormatter.format(Instant.ofEpochMilli(message.timestamp()))
-            // print the value
-            println("[${time}] ${message.value()}°F")
-        }
+        messages.forEach { message -> this.callback(message) }
     }
 
     /**

src/main/kotlin/fr/faraphel/m1_pe_kafka/rest/PingEndpoint.kt

@@ -0,0 +1,20 @@
+package fr.faraphel.m1_pe_kafka.rest
+
+import jakarta.ws.rs.GET
+import jakarta.ws.rs.Path
+
+
+/**
+ * A simple ping endpoint for the API
+ * Always answer "Pong!"
+ * Can be used to test if the API can be reached
+ */
+@Path("ping")
+class PingEndpoint {
+    /**
+     * Handler for a GET request on this endpoint
+     * @return "Pong!"
+     */
+    @GET
+    fun get(): String = "Pong!"
+}

src/main/kotlin/fr/faraphel/m1_pe_kafka/rest/TemperatureEndpoint.kt

@@ -0,0 +1,32 @@
+package fr.faraphel.m1_pe_kafka.rest
+
+import jakarta.ws.rs.GET
+import jakarta.ws.rs.Path
+
+
+/**
+ * This API endpoint return the latest temperature measured (in Fahrenheit)
+ */
+@Path("temperature")
+class TemperatureEndpoint {
+    companion object {
+        private var temperature: Double? = null  ///< the latest temperature value
+
+        /**
+         * Setter to update the latest temperature value
+         * @param temperature the new temperature value
+         */
+        fun setTemperature(temperature: Double) {
+            this.temperature = temperature
+        }
+    }
+
+    /**
+     * Handler for a GET request on this endpoint
+     * @return the latest temperature measured
+     */
+    @GET
+    fun get(): Double? {
+        return temperature
+    }
+}