Upstreams, targets and health

Key points

• An Upstream is a named pool; Targets are the instances in it, each with a weight.
• Point a Service at the upstream name and Kong load balances across the targets for you.
• Weight is relative, so weight: 100 and weight: 900 is a 10/90 split - handy for canaries.
• Active health checks probe targets on a timer; passive checks watch real traffic for failures.
• An unhealthy target is skipped automatically and returns when it passes again.

Example

upstreams:
  - name: orders-pool
    targets:
      - target: orders-1.internal:8080
        weight: 900                    # 90% of traffic
      - target: orders-2.internal:8080
        weight: 100                    # 10% - the canary
    healthchecks:
      active:
        http_path: /health
        healthy:   { interval: 5, successes: 2 }
        unhealthy: { interval: 5, http_failures: 3 }

Weights give you canaries, health checks give you self-healing - together they are a safe rollout.