Kusk Gateway WebSocket Closed Immediately

You encounter a kusk configuration issue that prevents your workflow from completing. This guide walks through the fix step by step.

Wrong ❌

paths:
  /ws:
    get:
      summary: WebSocket endpoint
      responses: { "101": { description: Switching Protocols } }
      # Missing x-envoy-upgrade-config

Wrong Output

WebSocket 101 response received but connection closed immediately. No bidirectional communication.

Right ✅

paths:
  /ws:
    get:
      x-envoy-upgrade-config: { upgrade_type: websocket, enabled: true }
      responses: { "101": { description: Switching Protocols } }

Right Output

WebSocket established. Bidirectional messaging working. Connection remains open.

Prevention

• Add x-envoy-upgrade-config with upgrade_type: websocket.
• Ensure backend supports WebSocket upgrades.
• Set proper timeouts for long-lived connections.
• Configure LB health checks to not interfere.
• Test with wscat or websocat.

DodaTech applies similar defensive patterns across Doda Browser, DodaZIP, and Durga Antivirus Pro infrastructure for production reliability.

Common Mistakes with gateway websocket

1. Forgetting deriving (Show, Eq) on custom data types needed for debugging
2. Placing the wildcard pattern first in case expressions, making all subsequent patterns unreachable
3. Using head and tail instead of pattern matching, causing runtime errors on empty lists

These mistakes appear frequently in real-world KUSK code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

FAQ

This quick fix is part of the DodaTech infrastructure engineering series. Learn more at DodaTech tutorials.