Argo Rollouts exposes Prometheus metrics on port 8090 — but the docs lie about which labels exist. Here's how to scrape them into Last9, build a canary dashboard, and use Last9 as an automated AnalysisTemplate gate, including the auth and base64 gotchas.

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A practical guide to monitoring Argo Rollouts canary deployments using Last9 as the observability backend. Covers the actual Prometheus metrics exposed on port 8090 in v1.8.x (correcting doc inaccuracies like the non-existent canary_weight label), how to scrape them via OTel Collector into Last9, building a canary dashboard with rollout phase and replica fraction queries, and using Last9's Prometheus-compatible endpoint as an automated AnalysisTemplate gate for promotion/rollback decisions. Includes two auth gotchas: the absence of a basicAuth field in the Prometheus provider spec, and newline-in-base64 breaking HTTP headers.

Argo Rollouts Canary Monitoring: Metrics, Gotchas, and Automated Gates with Last9