cad-krw-monitor

A lightweight Go service that monitors the CAD/KRW exchange rate, sends Discord alerts, and pushes metrics to Grafana Cloud.

How it works

GitHub Actions (every 20 min)
        ↓ POST /check
Render Web Service (free)
        ↓
  - Fetch CAD/KRW rate (Yahoo Finance → open.er-api.com fallback)
  - Push metrics → Grafana Cloud (Graphite) 📊
  - Send alerts  → Discord 🔔
  - Background goroutine checks every 5 min while awake

Alerts

• ⏰ Hourly — regular rate update every hour (:00)
• 🚨 Spike — immediate alert when rate moves ±0.5% or more (:00, :20, :40)
• 🎯 Target — alert when rate hits your target price

Data Sources

1. Yahoo Finance (primary) — real-time CAD/KRW rate
2. open.er-api.com (fallback) — hourly updates, no API key required

Stack

• Go — HTTP server
• Render — free web service hosting
• GitHub Actions — cron trigger (3x per hour, free on public repos)
• Grafana Cloud — metrics dashboard via Graphite (free tier)
• Discord — alert notifications

Environment Variables

Variable	Required	Description
DISCORD_WEBHOOK_URL	✅	Discord webhook URL
CHECK_SECRET	✅	Secret header for /check endpoint security
GRAPHITE_URL	✅	Grafana Cloud Graphite ingest URL
GRAPHITE_USER	✅	Grafana Cloud Graphite user ID (numeric)
GRAPHITE_API_KEY	✅	Grafana Cloud access policy token
TARGET_RATE	❌	Target rate in KRW (e.g. 1065)
TARGET_DIRECTION	❌	above or below (default: above)

Deployment

1. Render

• New → Blueprint → connect this repo
• Set environment variables in Render dashboard
• Copy the service URL (e.g. https://cad-krw-monitor.onrender.com)

2. GitHub Secrets

Repo → Settings → Secrets and variables → Actions:

• RENDER_URL — your Render service URL
• CHECK_SECRET — same value as set in Render

3. Grafana Cloud

• grafana.com → My Account → your stack → Graphite → Details
• Copy ingest URL, user ID, and generate an access policy token with metrics:write scope
• Add to Render env vars

4. Test

GitHub Actions → Check Rate (Hourly :00) → Run workflow

Check Discord for the alert and Grafana for the metric.

GitHub Actions Workflows

Workflow	Schedule	Action
check-00.yml	Every hour at :00	Spike check + hourly update
check-20.yml	Every hour at :20	Spike check
check-40.yml	Every hour at :40	Spike check

Grafana Dashboard

After data starts flowing:

1. Grafana → Dashboards → New → New Dashboard
2. Add visualization → Data source: Graphite
3. Metric: cad_krw.rate
4. Save as CAD/KRW Monitor

Background Checker

When the server is awake (after a GitHub Actions call), a background goroutine checks the rate every 5 minutes for spike detection. The server sleeps after ~15 minutes of inactivity on Render's free tier.

Endpoints

Endpoint	Method	Description
/check?hourly=true	POST	Fetch rate, push to Grafana, send hourly Discord update
/check	POST	Fetch rate, push to Grafana, spike/target check only
/health	GET	Health check