feat: add metrics for user registrations, logins, challenges, and game writebacks

modules/core/src/main/scala/de/nowchess/chess/engine/GameEngine.scala

@@ -17,10 +17,12 @@ import de.nowchess.chess.observer.*
 import de.nowchess.api.error.GameError
 import de.nowchess.api.game.WinReason.{Checkmate, Resignation}
 import de.nowchess.api.io.{GameContextExport, GameContextImport}
-import de.nowchess.api.rules.RuleSet
+import de.nowchess.api.rules.{PostMoveStatus, RuleSet}
 
+import io.micrometer.core.instrument.{Counter, MeterRegistry, Timer}
 import java.time.Instant
 import java.util.concurrent.{Executors, ScheduledExecutorService, ScheduledFuture, TimeUnit}
+import java.util.concurrent.atomic.AtomicInteger
 
 /** Pure game engine that manages game state and notifies observers of state changes. All rule queries delegate to the
   * injected RuleSet. All user interactions go through Commands; state changes are broadcast via GameEvents.
@@ -33,6 +35,7 @@ class GameEngine(
     initialDrawOffer: Option[Color] = None,
     initialRedoStack: List[Move] = Nil,
     initialTakebackRequest: Option[Color] = None,
+    private val meterRegistry: Option[MeterRegistry] = None,
 ) extends Observable:
   // Ensure that initialBoard is set correctly for threefold repetition detection
   private val contextWithInitialBoard =
@@ -57,6 +60,17 @@ class GameEngine(
   @SuppressWarnings(Array("DisableSyntax.var"))
   private var pendingTakebackRequest: Option[Color] = initialTakebackRequest
 
+  meterRegistry.foreach { reg =>
+    GameEngine.activeGamesCount.incrementAndGet()
+    reg.counter("nowchess.games.started").increment()
+  }
+  private def gamesCompletedCounter(result: String): Counter =
+    meterRegistry.map(_.counter("nowchess.games.completed", "result", result)).orNull
+  private def movesProcessedCounter: Counter =
+    meterRegistry.map(_.counter("nowchess.moves.processed")).orNull
+  private def movesDurationTimer: Timer =
+    meterRegistry.map(_.timer("nowchess.moves.duration")).orNull
+
   // Start scheduler immediately for live clocks so passive expiry fires without waiting for a move.
   clockState.foreach(scheduleExpiryCheck)
 
@@ -165,6 +179,8 @@ class GameEngine(
       pendingTakebackRequest = None
       stopClock()
       redoStack = Nil
+      Option(gamesCompletedCounter("resignation")).foreach(_.increment())
+      GameEngine.activeGamesCount.decrementAndGet()
       notifyObservers(ResignEvent(currentContext, color))
   }
 
@@ -197,6 +213,8 @@ class GameEngine(
           pendingTakebackRequest = None
           stopClock()
           redoStack = Nil
+          Option(gamesCompletedCounter("draw.agreement")).foreach(_.increment())
+          GameEngine.activeGamesCount.decrementAndGet()
           notifyObservers(DrawEvent(currentContext, DrawReason.Agreement))
   }
 
@@ -223,11 +241,15 @@ class GameEngine(
       currentContext = currentContext.withResult(Some(GameResult.Draw(DrawReason.FiftyMoveRule)))
       stopClock()
       redoStack = Nil
+      Option(gamesCompletedCounter("draw.fifty_move")).foreach(_.increment())
+      GameEngine.activeGamesCount.decrementAndGet()
       notifyObservers(DrawEvent(currentContext, DrawReason.FiftyMoveRule))
     else if ruleSet.isThreefoldRepetition(currentContext) then
       currentContext = currentContext.withResult(Some(GameResult.Draw(DrawReason.ThreefoldRepetition)))
       stopClock()
       redoStack = Nil
+      Option(gamesCompletedCounter("draw.threefold")).foreach(_.increment())
+      GameEngine.activeGamesCount.decrementAndGet()
       notifyObservers(DrawEvent(currentContext, DrawReason.ThreefoldRepetition))
     else notifyObservers(InvalidMoveEvent(currentContext, InvalidMoveReason.DrawCannotBeClaimed))
   }
@@ -311,9 +333,18 @@ class GameEngine(
       currentContext = currentContext.withResult(Some(GameResult.Draw(reason)))
       stopClock()
       redoStack = Nil
+      Option(gamesCompletedCounter(drawReasonTag(reason))).foreach(_.increment())
+      GameEngine.activeGamesCount.decrementAndGet()
       notifyObservers(DrawEvent(currentContext, reason))
   }
 
+  private def drawReasonTag(reason: DrawReason): String = reason match
+    case DrawReason.Agreement            => "draw.agreement"
+    case DrawReason.FiftyMoveRule        => "draw.fifty_move"
+    case DrawReason.ThreefoldRepetition  => "draw.threefold"
+    case DrawReason.Stalemate            => "draw.stalemate"
+    case DrawReason.InsufficientMaterial => "draw.insufficient"
+
   /** Inject clock state directly (for testing). */
   private[engine] def injectClockState(cs: Option[ClockState]): Unit = synchronized { clockState = cs }
 
@@ -334,6 +365,11 @@ class GameEngine(
     pendingDrawOffer = None
     pendingTakebackRequest = None
     redoStack = Nil
+    val tag = result match
+      case GameResult.Draw(_) => "draw.insufficient"
+      case _                  => "timeout"
+    Option(gamesCompletedCounter(tag)).foreach(_.increment())
+    activeGamesCount.decrementAndGet()
     notifyObservers(TimeFlagEvent(currentContext, flagged))
 
   private def scheduleExpiryCheck(cs: ClockState): Unit =
@@ -369,6 +405,12 @@ class GameEngine(
   // ──── Private helpers ────
 
   private def executeMove(move: Move): Unit =
+    Option(movesDurationTimer) match
+      case Some(timer) => timer.record(() => executeMoveBody(move))
+      case None        => executeMoveBody(move)
+    Option(movesProcessedCounter).foreach(_.increment())
+
+  private def executeMoveBody(move: Move): Unit =
     if !isRedoing then
       redoStack = Nil
       pendingTakebackRequest = None
@@ -391,28 +433,36 @@ class GameEngine(
     )
 
     val status = ruleSet.postMoveStatus(currentContext)
-    if currentContext.result.isEmpty then
-      if status.isCheckmate then
-        val winner = currentContext.turn.opposite
-        currentContext = currentContext.withResult(Some(GameResult.Win(winner, Checkmate)))
-        cancelScheduled()
-        notifyObservers(CheckmateEvent(currentContext, winner))
-        redoStack = Nil
-      else if status.isStalemate then
-        currentContext = currentContext.withResult(Some(GameResult.Draw(DrawReason.Stalemate)))
-        cancelScheduled()
-        notifyObservers(DrawEvent(currentContext, DrawReason.Stalemate))
-        redoStack = Nil
-      else if status.isInsufficientMaterial then
-        currentContext = currentContext.withResult(Some(GameResult.Draw(DrawReason.InsufficientMaterial)))
-        cancelScheduled()
-        notifyObservers(DrawEvent(currentContext, DrawReason.InsufficientMaterial))
-        redoStack = Nil
-      else if status.isCheck then notifyObservers(CheckDetectedEvent(currentContext))
+    if currentContext.result.isEmpty then applyPostMoveStatus(status)
 
     if currentContext.halfMoveClock >= 100 then notifyObservers(FiftyMoveRuleAvailableEvent(currentContext))
     if status.isThreefoldRepetition then notifyObservers(ThreefoldRepetitionAvailableEvent(currentContext))
 
+  private def applyPostMoveStatus(status: PostMoveStatus): Unit =
+    if status.isCheckmate then
+      val winner = currentContext.turn.opposite
+      currentContext = currentContext.withResult(Some(GameResult.Win(winner, Checkmate)))
+      cancelScheduled()
+      Option(gamesCompletedCounter("checkmate")).foreach(_.increment())
+      GameEngine.activeGamesCount.decrementAndGet()
+      notifyObservers(CheckmateEvent(currentContext, winner))
+      redoStack = Nil
+    else if status.isStalemate then
+      currentContext = currentContext.withResult(Some(GameResult.Draw(DrawReason.Stalemate)))
+      cancelScheduled()
+      Option(gamesCompletedCounter("draw.stalemate")).foreach(_.increment())
+      GameEngine.activeGamesCount.decrementAndGet()
+      notifyObservers(DrawEvent(currentContext, DrawReason.Stalemate))
+      redoStack = Nil
+    else if status.isInsufficientMaterial then
+      currentContext = currentContext.withResult(Some(GameResult.Draw(DrawReason.InsufficientMaterial)))
+      cancelScheduled()
+      Option(gamesCompletedCounter("draw.insufficient")).foreach(_.increment())
+      GameEngine.activeGamesCount.decrementAndGet()
+      notifyObservers(DrawEvent(currentContext, DrawReason.InsufficientMaterial))
+      redoStack = Nil
+    else if status.isCheck then notifyObservers(CheckDetectedEvent(currentContext))
+
   private def translateMoveToNotation(move: Move, boardBefore: Board): String =
     move.moveType match
       case MoveType.CastleKingside    => "O-O"
@@ -526,3 +576,6 @@ class GameEngine(
           pendingTakebackRequest = None
           notifyObservers(TakebackDeclinedEvent(currentContext, color))
   }
+
+object GameEngine:
+  val activeGamesCount: AtomicInteger = new AtomicInteger(0)

modules/core/src/main/scala/de/nowchess/chess/registry/RedisGameRegistry.scala

@@ -12,7 +12,9 @@ import de.nowchess.chess.grpc.RuleSetGrpcAdapter
 import de.nowchess.chess.config.RedisConfig
 import de.nowchess.chess.grpc.IoGrpcClientWrapper
 import de.nowchess.chess.resource.GameDtoMapper
+import io.micrometer.core.instrument.{Gauge, MeterRegistry}
 import io.quarkus.redis.datasource.RedisDataSource
+import jakarta.annotation.PostConstruct
 import jakarta.enterprise.context.ApplicationScoped
 import jakarta.inject.Inject
 import org.eclipse.microprofile.rest.client.inject.RestClient
@@ -34,12 +36,20 @@ class RedisGameRegistry extends GameRegistry:
   @Inject var ioClient: IoGrpcClientWrapper               = uninitialized
   @Inject var ruleSetAdapter: RuleSetGrpcAdapter          = uninitialized
   @Inject @RestClient var storeClient: StoreServiceClient = uninitialized
+  @Inject var meterRegistry: MeterRegistry                = uninitialized
   // scalafix:on
 
   private val log          = Logger.getLogger(classOf[RedisGameRegistry])
   private val localEngines = ConcurrentHashMap[String, GameEntry]()
   private val rng          = new SecureRandom()
 
+  @PostConstruct
+  def initMetrics(): Unit =
+    Gauge
+      .builder("nowchess.games.active", GameEngine.activeGamesCount, _.get().toDouble)
+      .register(meterRegistry)
+    ()
+
   private def cacheKey(gameId: String) = s"${redisConfig.prefix}:game:entry:$gameId"
 
   def generateId(): String =
@@ -58,14 +68,17 @@ class RedisGameRegistry extends GameRegistry:
     )
 
   def get(gameId: String): Option[GameEntry] =
-    Option(localEngines.get(gameId)) match
+    val result = Option(localEngines.get(gameId)) match
       case Some(localEntry) =>
+        meterRegistry.counter("nowchess.games.cache.hits", "source", "local").increment()
         readRedisDto(gameId).flatMap(dto => Try(reconstruct(dto)).toOption) match
           case Some(redisEntry) if !sameSnapshot(localEntry, redisEntry) =>
             localEngines.put(gameId, redisEntry)
             Some(redisEntry)
           case _ => Some(localEntry)
       case None => fromRedis(gameId).orElse(fromDb(gameId))
+    if result.isEmpty then meterRegistry.counter("nowchess.games.cache.misses").increment()
+    result
 
   def update(entry: GameEntry): Unit =
     localEngines.put(entry.gameId, entry)
@@ -86,6 +99,7 @@ class RedisGameRegistry extends GameRegistry:
         }
       }
       .map { entry =>
+        meterRegistry.counter("nowchess.games.cache.hits", "source", "redis").increment()
         localEngines.put(gameId, entry)
         log.infof("Loaded game %s from Redis cache", gameId)
         entry
@@ -118,6 +132,7 @@ class RedisGameRegistry extends GameRegistry:
       (dto, reconstruct(dto))
     } match
       case scala.util.Success((dto, entry)) =>
+        meterRegistry.counter("nowchess.games.cache.hits", "source", "db").increment()
         log.infof("Loaded game %s from store service", gameId)
         localEngines.put(gameId, entry)
         redis.value(classOf[String]).setex(cacheKey(gameId), 1800L, objectMapper.writeValueAsString(dto))

modules/core/src/main/scala/de/nowchess/chess/service/InstanceHeartbeatService.scala

@@ -19,6 +19,8 @@ import de.nowchess.coordinator.proto.{CoordinatorServiceGrpc, *}
 import de.nowchess.coordinator.proto.CoordinatorServiceGrpc.CoordinatorServiceStub
 import io.grpc.stub.StreamObserver
 import io.grpc.Channel
+import io.micrometer.core.instrument.{Gauge, MeterRegistry}
+import java.util.concurrent.atomic.AtomicInteger
 
 @ApplicationScoped
 class InstanceHeartbeatService:
@@ -32,6 +34,9 @@ class InstanceHeartbeatService:
   @Inject
   private var mapper: ObjectMapper = uninitialized
 
+  @Inject
+  private var meterRegistry: MeterRegistry = uninitialized
+
   @GrpcClient("coordinator-grpc")
   private var channel: Channel = uninitialized
 
@@ -51,14 +56,15 @@ class InstanceHeartbeatService:
   private var streamObserver: Option[StreamObserver[HeartbeatFrame]] = None
   private var heartbeatExecutor                                      = Executors.newScheduledThreadPool(1)
   private var redisHeartbeatExecutor                                 = Executors.newScheduledThreadPool(1)
-  private var subscriptionCount                                      = 0
   private var localCacheSize                                         = 0
   private var serviceActive                                          = false
   private var shuttingDown                                           = false
   // scalafix:on DisableSyntax.var
   private val redisHeartbeatPending = new AtomicBoolean(false)
+  private val subscriptionCount     = new AtomicInteger(0)
 
   def onStart(@Observes event: StartupEvent): Unit =
+    Gauge.builder("nowchess.instance.subscriptions", subscriptionCount, _.get().toDouble).register(meterRegistry)
     if coordinatorEnabled then
       try
         shuttingDown = false
@@ -90,7 +96,7 @@ class InstanceHeartbeatService:
     redisPrefix = prefix
 
   def setSubscriptionCount(count: Int): Unit =
-    subscriptionCount = count
+    subscriptionCount.set(count)
 
   def setLocalCacheSize(count: Int): Unit =
     localCacheSize = count
@@ -99,13 +105,13 @@ class InstanceHeartbeatService:
     if coordinatorEnabled then
       val setKey = s"$redisPrefix:instance:$instanceId:games"
       redis.set(classOf[String]).sadd(setKey, gameId)
-      subscriptionCount += 1
+      subscriptionCount.incrementAndGet()
 
   def removeGameSubscription(gameId: String): Unit =
     if coordinatorEnabled then
       val setKey = s"$redisPrefix:instance:$instanceId:games"
       redis.set(classOf[String]).srem(setKey, gameId)
-      subscriptionCount = Math.max(0, subscriptionCount - 1)
+      subscriptionCount.updateAndGet(c => Math.max(0, c - 1))
 
   private def generateInstanceId(): Unit =
     val hostname =
@@ -162,13 +168,14 @@ class InstanceHeartbeatService:
           .setHostname(getHostname)
           .setHttpPort(httpPort)
           .setGrpcPort(grpcPort)
-          .setSubscriptionCount(subscriptionCount)
+          .setSubscriptionCount(subscriptionCount.get())
           .setLocalCacheSize(localCacheSize)
           .setTimestampMillis(System.currentTimeMillis())
           .build()
         observer.onNext(frame)
       catch
         case ex: Exception =>
+          meterRegistry.counter("nowchess.heartbeat.failures").increment()
           log.warnf(ex, "Failed to send heartbeat frame")
     }
 
@@ -182,7 +189,7 @@ class InstanceHeartbeatService:
           "hostname"          -> getHostname,
           "httpPort"          -> httpPort,
           "grpcPort"          -> grpcPort,
-          "subscriptionCount" -> subscriptionCount,
+          "subscriptionCount" -> subscriptionCount.get(),
           "localCacheSize"    -> localCacheSize,
           "lastHeartbeat"     -> java.time.Instant.now().toString,
           "state"             -> "HEALTHY",