fix: enhance AutoScaler and InstanceRegistry for replica management and stale instance eviction

modules/coordinator/src/main/scala/de/nowchess/coordinator/service/AutoScaler.scala

@@ -74,11 +74,11 @@ class AutoScaler:
                   val maxReplicas     = config.scaleMaxReplicas
 
                   if currentReplicas < maxReplicas then
-                    spec.put("replicas", String.valueOf(currentReplicas + 1))
+                    spec.put("replicas", Integer.valueOf(currentReplicas + 1))
                     kube
-                      .resources(classOf[GenericKubernetesResource])
+                      .genericKubernetesResources(argoApiVersion, argoKind)
                       .inNamespace(config.k8sNamespace)
-                      .withName(config.k8sRolloutName)
+                      .resource(rollout)
                       .update()
                     log.infof(
                       "Scaled up %s from %d to %d replicas",
@@ -115,11 +115,11 @@ class AutoScaler:
                   val minReplicas     = config.scaleMinReplicas
 
                   if currentReplicas > minReplicas then
-                    spec.put("replicas", String.valueOf(currentReplicas - 1))
+                    spec.put("replicas", Integer.valueOf(currentReplicas - 1))
                     kube
-                      .resources(classOf[GenericKubernetesResource])
+                      .genericKubernetesResources(argoApiVersion, argoKind)
                       .inNamespace(config.k8sNamespace)
-                      .withName(config.k8sRolloutName)
+                      .resource(rollout)
                       .update()
                     log.infof(
                       "Scaled down %s from %d to %d replicas",

modules/coordinator/src/main/scala/de/nowchess/coordinator/service/HealthMonitor.scala

@@ -39,6 +39,8 @@ class HealthMonitor:
     redisPrefix = prefix
 
   def checkInstanceHealth: Unit =
+    val evicted = instanceRegistry.evictStaleInstances(config.heartbeatTtl)
+    if evicted.nonEmpty then log.warnf("Evicted %d stale instances: %s", evicted.size, evicted.mkString(", "))
     val instances = instanceRegistry.getAllInstances
     instances.foreach { inst =>
       val isHealthy = checkHealth(inst.instanceId)

modules/coordinator/src/main/scala/de/nowchess/coordinator/service/InstanceRegistry.scala

@@ -8,6 +8,7 @@ import scala.compiletime.uninitialized
 import com.fasterxml.jackson.databind.ObjectMapper
 import de.nowchess.coordinator.dto.InstanceMetadata
 import java.util.concurrent.ConcurrentHashMap
+import java.time.{Duration, Instant}
 import io.smallrye.mutiny.Uni
 import org.jboss.logging.Logger
 
@@ -68,3 +69,20 @@ class InstanceRegistry:
   def removeInstance(instanceId: String): Unit =
     instances.remove(instanceId)
     log.infof("Instance %s removed from registry", instanceId)
+
+  def evictStaleInstances(maxAge: Duration): List[String] =
+    val cutoff = Instant.now().minus(maxAge)
+    val stale = instances.asScala
+      .collect { case (id, inst) =>
+        try
+          if Instant.parse(inst.lastHeartbeat).isBefore(cutoff) then Some(id)
+          else None
+        catch case _: Exception => None
+      }
+      .flatten
+      .toList
+    stale.foreach { id =>
+      instances.remove(id)
+      log.warnf("Evicted stale instance %s (heartbeat older than %s)", id, maxAge)
+    }
+    stale