Load Balancer Health-Check Diagnostics

Diagnose health-check issues on Alibaba Cloud load balancers: "health check failed", "backend server unhealthy", "listener health check configuration", "which backends are being probed and why they fail".

Core approach: route to the matching diagnosis script by instance ID prefix, collect listeners, forwarding rules, server groups and per-backend probe status, then deliver a structured report plus per-server self-check commands.

Observability

All OpenAPI calls (invoked through the aliyun CLI) include:

• User-Agent: --user-agent AlibabaCloud-Agent-Skills/{SKILL_NAME}/{session-id}
• SKILL_NAME: alibabacloud-lb-healthcheck
• session-id: 32-character hex string generated per diagnostic session

Prerequisites

1. aliyun CLI 3.x with the slb, alb, nlb and vpc plugins installed. All API calls go through the CLI plugin mode (e.g. aliyun slb describe-health-status); there are no Python SDK dependencies.
2. Alibaba Cloud credentials — resolved automatically by the aliyun CLI default credential chain (environment variables or ~/.aliyun/config.json). Do not read, print, or pass AK/SK/STS tokens explicitly.
3. Target inputs: the load balancer instance ID (required) and the region (optional, auto-resolvable; see Missing Information Handling).