fix accumulation

readme.connections.md

@@ -673,4 +673,52 @@ if (!record.connectionClosed && record.outgoing && record.bytesReceived > 0 && r
 - Connection is older than 60 seconds
 - Both sockets are still alive (not destroyed)
 
-This complements the zombie detection by handling cases where sockets remain technically alive but the connection is effectively dead.
+This complements the zombie detection by handling cases where sockets remain technically alive but the connection is effectively dead.
+
+## 🚨 CRITICAL FIX: Cleanup Queue Bug (January 2025)
+
+### Critical Bug Found
+The cleanup queue had a severe bug that caused connection accumulation when more than 100 connections needed cleanup:
+
+```typescript
+// BUG: This cleared the ENTIRE queue after processing only the first batch!
+const toCleanup = Array.from(this.cleanupQueue).slice(0, this.cleanupBatchSize);
+this.cleanupQueue.clear(); // ❌ This discarded all connections beyond the first 100!
+```
+
+### Fix Implemented
+```typescript
+// Now only removes the connections being processed
+const toCleanup = Array.from(this.cleanupQueue).slice(0, this.cleanupBatchSize);
+for (const connectionId of toCleanup) {
+  this.cleanupQueue.delete(connectionId); // ✅ Only remove what we process
+  const record = this.connectionRecords.get(connectionId);
+  if (record) {
+    this.cleanupConnection(record, record.incomingTerminationReason || 'normal');
+  }
+}
+```
+
+### Impact
+- **Before**: If 150 connections needed cleanup, only the first 100 would be processed and the remaining 50 would accumulate forever
+- **After**: All connections are properly cleaned up in batches
+
+### Additional Improvements
+
+1. **Faster Inactivity Checks**: Reduced from 30s to 10s intervals
+   - Zombies and stuck connections are detected 3x faster
+   - Reduces the window for accumulation
+
+2. **Duplicate Prevention**: Added check in queueCleanup to prevent processing already-closed connections
+   - Prevents unnecessary work
+   - Ensures connections are only cleaned up once
+
+### Summary of All Fixes
+
+1. **Connection Timeout** (already documented) - Prevents accumulation when backends are unreachable
+2. **Zombie Detection** - Cleans up connections with destroyed sockets
+3. **Stuck Connection Detection** - Cleans up connections to hanging backends
+4. **Cleanup Queue Bug** - Ensures ALL connections get cleaned up, not just the first 100
+5. **Faster Detection** - Reduced check interval from 30s to 10s
+
+These fixes combined should prevent connection accumulation in all known scenarios.