chmonitorAlerting to Slack and Discord
Wire chmonitor's health sweep to a Slack or Discord incoming webhook so your team gets notified the moment a check crosses a threshold — no polling the dashboard required.
chmonitor's Health page checks replication lag, failed mutations, disk usage and a handful of other signals on a schedule you control. Left alone, that only helps the person who remembers to look at the page. The health-sweep cron endpoint closes that gap: point it at a Slack or Discord incoming webhook and it posts a message whenever a check meets or exceeds a severity threshold.
This page walks through creating the webhook URL itself. For the full
CRON_SECRET / HEALTH_ALERT_* environment variable reference, scheduling on
Cloudflare Cron, and the sequence diagram, see
Health → Health-sweep cron alerting.
Prerequisites
- A chmonitor instance already connected to at least one ClickHouse host.
- The ability to set environment variables / secrets on your deployment (Cloudflare Worker secret, Docker env, or Kubernetes Secret).
1. Create the webhook URL
- Go to api.slack.com/apps → create (or open) an app → Incoming Webhooks → turn the toggle on.
- Add New Webhook to Workspace, pick the channel, and copy the generated
URL (
https://hooks.slack.com/services/...).
- In the target channel: Channel Settings → Integrations → Webhooks → New Webhook.
- Name it, optionally set an avatar, and Copy Webhook URL.
The same URL works for both — the sweep posts {"text": "...", "content": "..."},
and each platform reads the field it understands.
2. Configure and enable
CRON_SECRET=<random-secret>
HEALTH_ALERT_ENABLED=true
HEALTH_ALERT_MIN_SEVERITY=warning # or "critical" to only page on the worst checks
HEALTH_ALERT_WEBHOOK_URL=<the URL you copied above>On Cloudflare Workers, set the secrets rather than plain vars:
wrangler secret put CRON_SECRET
wrangler secret put HEALTH_ALERT_WEBHOOK_URL3. Test it
curl -H "Authorization: Bearer $CRON_SECRET" \
https://your-chmonitor.example.com/api/cron/health-sweepThe endpoint always returns HTTP 200 with a JSON array of check results —
dispatch happens server-side and doesn't block the response. To confirm a
message actually went out, trip a threshold intentionally (temporarily lower
HEALTH_ALERT_MIN_SEVERITY to warning) and watch the channel.
Alert history
On Cloud with D1 configured, the Health page's alert history records every dispatch attempt and whether delivery succeeded. That history isn't available on a self-hosted deployment without D1.