feat(notification-service): add Dockerfile, actuator health and alert deduplication

Add multi-stage Dockerfile with eclipse-temurin:17 and HEALTHCHECK on /actuator/health.
Expose /actuator/health endpoint via spring-boot-starter-actuator.
Deduplicate alerts: only notify when a room's CO2 level changes, reset on recovery.

Assisted-by: Claude:claude-sonnet-4-6

notification_service/Dockerfile

@@ -0,0 +1,20 @@
+# ── Stage 1 : build ──────────────────────────────────────────────────────────
+FROM eclipse-temurin:17-jdk-alpine AS builder
+WORKDIR /app
+
+COPY pom.xml .
+COPY src ./src
+
+RUN apk add --no-cache maven && mvn package -DskipTests -q
+
+# ── Stage 2 : run ─────────────────────────────────────────────────────────────
+FROM eclipse-temurin:17-jre-alpine
+WORKDIR /app
+
+COPY --from=builder /app/target/notification-service-*.jar app.jar
+
+EXPOSE 8080
+HEALTHCHECK --interval=30s --timeout=5s --retries=3 \
+  CMD wget -qO- http://localhost:8080/actuator/health || exit 1
+
+ENTRYPOINT ["java", "-jar", "app.jar"]

notification_service/pom.xml

@@ -37,6 +37,10 @@
       <artifactId>spring-dotenv</artifactId>
       <version>4.0.0</version>
     </dependency>
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-actuator</artifactId>
+    </dependency>
 
     <dependency>
       <groupId>org.springframework.boot</groupId>

notification_service/src/main/java/ch/hesso/pi/notification/scheduler/AirQualityScheduler.java

@@ -12,6 +12,8 @@ import org.springframework.stereotype.Component;
 
 import java.time.Instant;
 import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 
 @Component
 public class AirQualityScheduler {
@@ -28,6 +30,9 @@ public class AirQualityScheduler {
     private final TelegramNotificationService telegramService;
     private final NotificationProperties      props;
 
+    // last alerted level per room — null means no alert is active for that room
+    private final Map<String, Co2Level> lastAlertedLevel = new ConcurrentHashMap<>();
+
     public AirQualityScheduler(AirQualityService airQualityService,
                                 TelegramNotificationService telegramService,
                                 NotificationProperties props) {
@@ -36,8 +41,8 @@ public class AirQualityScheduler {
         this.props             = props;
     }
 
-    @Scheduled(fixedDelayString    = "${notification.air-quality.poll-interval-ms:60000}",
+    @Scheduled(fixedDelayString   = "${notification.air-quality.poll-interval-ms:60000}",
-               initialDelayString  = "5000")
+               initialDelayString = "5000")
     public void checkAirQuality() {
         boolean mockMode = props.getAirQuality().isMockMode();
         log.debug("Polling air quality data… (mock={})", mockMode);
@@ -53,9 +58,19 @@ public class AirQualityScheduler {
 
         for (SensorReading reading : readings) {
             Co2Level level = airQualityService.resolveLevel(reading.co2());
+
             if (airQualityService.isAlertable(level)) {
-                log.info("Alertable reading: room={} co2={} level={}", reading.roomId(), reading.co2(), level);
+                Co2Level previous = lastAlertedLevel.get(reading.roomId());
-                telegramService.sendAlert(reading, level);
+                if (level != previous) {
+                    log.info("Alert level changed: room={} {} -> {}", reading.roomId(), previous, level);
+                    telegramService.sendAlert(reading, level);
+                    lastAlertedLevel.put(reading.roomId(), level);
+                }
+            } else {
+                // room recovered — reset so next alert triggers a new notification
+                if (lastAlertedLevel.remove(reading.roomId()) != null) {
+                    log.info("Room {} recovered to {}", reading.roomId(), level);
+                }
             }
         }
     }

notification_service/src/main/resources/application.yml

@@ -2,6 +2,15 @@ spring:
   application:
     name: notification-service
 
+management:
+  endpoints:
+    web:
+      exposure:
+        include: health
+  endpoint:
+    health:
+      show-details: never
+
 notification:
   telegram:
     bot-token: ${TELEGRAM_BOT_TOKEN}