Fix blind spot where Caddy 502 errors were invisible: the dashboards and
alerts queried caddy_http_response_duration_seconds (upstream responses only),
missing 502s that Caddy generates itself. Switch to
caddy_http_request_duration_seconds (server-level, all responses).
Add Journal Grafana dashboard with: 502 rate, response codes, request rate
by route, latency percentiles, container restarts/memory/CPU, Node.js event
loop lag and heap, and Loki log panels for errors and Caddy 5xx entries.
Add color coding to Caddy status code panel (green=2xx, blue=3xx, yellow=4xx,
red=5xx). Add log-based error rate panel to the overview dashboard.
New alerts: container restart loop, PostgreSQL connections > 80, application
crash log detection (Loki), and Caddy 502 rate.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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