feat: 방 총 갯수 metrix 생성 구현

build.gradle

@@ -30,6 +30,9 @@ dependencies {
     testImplementation 'io.rest-assured:rest-assured:5.4.0'
 
     implementation 'org.springdoc:springdoc-openapi-starter-webmvc-ui:2.0.2'
+
+    implementation 'org.springframework.boot:spring-boot-starter-actuator'
+    implementation 'io.micrometer:micrometer-registry-prometheus'
 }
 
 tasks.named('test') {

src/main/java/mafia/mafiatogether/domain/RoomManager.java

@@ -38,4 +38,8 @@ public Room findByCode(final String code) {
     public boolean validateCode(final String code) {
         return !rooms.containsKey(code);
     }
+
+    public Integer getTotalRoomCount() {
+        return rooms.size();
+    }
 }

src/main/java/mafia/mafiatogether/service/RoomService.java

@@ -1,5 +1,7 @@
 package mafia.mafiatogether.service;
 
+import io.micrometer.core.instrument.Gauge;
+import io.micrometer.core.instrument.MeterRegistry;
 import java.time.Clock;
 import lombok.RequiredArgsConstructor;
 import mafia.mafiatogether.config.exception.ExceptionCode;
@@ -22,9 +24,11 @@
 public class RoomService {
 
     private final RoomManager roomManager;
+    private final MeterRegistry meterRegistry;
 
     public RoomCodeResponse create(final RoomCreateRequest request) {
         final String code = roomManager.create(request.toDomain());
+        Gauge.builder("room", roomManager, RoomManager::getTotalRoomCount).tag("info", "size").register(meterRegistry);
         return new RoomCodeResponse(code);
     }
 
@@ -57,7 +61,7 @@ public RoomValidateResponse validateCode(final String code) {
 
     public RoomResultResponse findResult(final String code) {
         final Room room = roomManager.findByCode(code);
-        if(!room.isEnd()){
+        if (!room.isEnd()) {
             throw new RoomException(ExceptionCode.GAME_IS_NOT_FINISHED);
         }
         return RoomResultResponse.of((EndStatus) room.getStatus());