From 4ec5b931de8177281092de3d0bc1a7061fa56ee5 Mon Sep 17 00:00:00 2001
From: Janis <janis.e.20@gmx.de>
Date: Sun, 17 May 2026 18:01:55 +0200
Subject: [PATCH] feat: integrate auto-scaler to handle instance health checks
 and scaling

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 COORDINATOR_BUGS.md | 125 --------------------------------------------
 1 file changed, 125 deletions(-)
 delete mode 100644 COORDINATOR_BUGS.md

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-# Coordinator Module - Bug Report
-
-## Critical Bugs
-
-### 1. Cache Eviction Kills Correspondence Games (HIGH)
-**File:** `CacheEvictionManager.scala:96-101`
-**Problem:** Uses `lastHeartbeat` timestamp from GameCacheDto to determine if game is idle. But `lastHeartbeat` is set at store/update time, not move time. Correspondence games with days between moves get evicted while active.
-
-**Current Code:**
-```scala
-private def extractLastUpdatedTimestamp(json: String): Long =
-  Try {
-    val parsed = objectMapper.readTree(json)
-    Option(parsed.get("lastHeartbeat"))
-      .filter(_.isTextual)
-      .fold(0L)(lh => Instant.parse(lh.asText()).toEpochMilli)
-  }.getOrElse(0L)
-```
-
-**Impact:** Active correspondence games deleted from cache after idle threshold (config-dependent, typically hours/days)
-**Fix:** Track actual move timestamp separately in GameCacheDto or check game state instead of heartbeat
-
----
-
-### 2. Concurrent Rebalance Race Condition (HIGH)
-**File:** `LoadBalancer.scala:108-115`
-**Problem:** `getGamesToMove()` reads games from Redis set but doesn't remove them atomically. If multiple rebalance calls run concurrently, same game can be selected in different batches and moved to multiple instances.
-
-**Current Code:**
-```scala
-private def getGamesToMove(instanceId: String, count: Int): List[String] =
-  try
-    val setKey = s"$redisPrefix:instance:$instanceId:games"
-    redis.set(classOf[String]).smembers(setKey).asScala.toList.take(count)  // Read-only, no removal
-  catch
-    case ex: Exception =>
-      log.debugf(ex, "Failed to get games for %s", instanceId)
-      List()
-```
-
-**Impact:** Game subscribed to 2+ instances, state corruption, double-processing
-**Fix:** Use Redis SPOP (atomic pop) or Lua script for atomic read+remove
-
----
-
-### 3. Pod Matching is Unreliable (MEDIUM)
-**File:** `HealthMonitor.scala:134, 188`
-**Problem:** Uses `.contains()` string matching for pod name. Pod "core-1" matches instance "core-11"; loose matching causes wrong pod operations.
-
-**Current Code:**
-```scala
-instanceId.contains(podName)  // Line 134
-// and
-pods.find(pod => instanceId.contains(pod.getMetadata.getName))  // Line 188
-```
-
-**Impact:** Wrong pod deleted/evicted when multiple similar names exist
-**Fix:** Exact match or structured ID encoding
-
----
-
-## Medium Priority Bugs
-
-### 4. Inefficient Game-to-Instance Lookup (MEDIUM)
-**File:** `CacheEvictionManager.scala:104-113`
-**Problem:** Linear scan through ALL instances to find which one holds a game. Runs per-game during eviction scan every 5 minutes.
-
-**Current Code:**
-```scala
-private def findInstanceWithGame(gameId: String): Option[InstanceMetadata] =
-  try
-    instanceRegistry.getAllInstances.find { instance =>  // O(n) instances
-      val setKey = s"$redisPrefix:instance:${instance.instanceId}:games"
-      redis.set(classOf[String]).sismember(setKey, gameId)
-    }
-```
-
-**Impact:** Eviction scans slow with many instances (100+ instances = 100+ Redis ops per game)
-**Fix:** Maintain `nowchess:game:$gameId:instance` → instanceId mapping in Redis
-
----
-
-### 5. Instance Registry Lookup on Pod Events (MEDIUM)
-**File:** `HealthMonitor.scala:245-247`
-**Problem:** Linear search through all instances every pod state change. Pod watch fires frequently.
-
-**Current Code:**
-```scala
-private def findRegisteredInstance(pod: Pod): Option[InstanceMetadata] =
-  val podName = pod.getMetadata.getName
-  instanceRegistry.getAllInstances.find(inst => inst.instanceId.contains(podName))
-```
-
-**Impact:** O(n) lookup on hot path (pod watch events)
-**Fix:** Maintain pod-name → instanceId index or use proper ID encoding
-
----
-
-## Low Priority Bugs
-
-### 6. Non-idiomatic Sorting (LOW)
-**File:** `LoadBalancer.scala:72`
-**Problem:** Uses `.sortBy[Int](_.subscriptionCount).reverse` instead of `.sortByDescending()`
-
-**Current Code:**
-```scala
-val overloaded = instances
-  .filter(_.subscriptionCount > config.maxGamesPerCore)
-  .sortBy[Int](_.subscriptionCount)  // Type annotation unnecessary
-  .reverse
-```
-
-**Impact:** Micro code-quality issue
-**Fix:** Use `.sortByDescending(_.subscriptionCount)`
-
----
-
-## Fix Priority
-
-1. **Cache eviction (HIGH)** — Data loss risk
-2. **Rebalance race (HIGH)** — State corruption risk
-3. **Pod matching (MEDIUM)** — Operational blast radius
-4. **Game lookup (MEDIUM)** — Performance under scale
-5. **Instance lookup (MEDIUM)** — Hot path perf
-6. **Sorting (LOW)** — Code style