---
checkId: check.notify.slack.connectivity
plugin: stellaops.doctor.notify
severity: warn
tags: [notify, slack, connectivity, network]
---
# Slack Connectivity

## What It Checks
Verifies that the configured Slack webhook endpoint is reachable. The check:

- Sends an empty-text POST payload to the webhook URL with a 10-second timeout.
- Slack returns `no_text` for empty messages, which proves the endpoint is alive without posting a visible message.
- Passes if the response is successful or contains `no_text`.
- Warns if an unexpected HTTP status is returned (e.g., invalid or revoked webhook).
- Fails on connection timeout or HTTP request exceptions.

The check only runs when `Notify:Channels:Slack:WebhookUrl` is set and is a valid absolute URL.

## Why It Matters
A configured but unreachable Slack webhook means notifications are silently dropped. Teams relying on Slack for release alerts and security findings will miss critical events.

## Common Causes
- Invalid or expired webhook URL
- Slack workspace configuration changed
- Webhook URL revoked or regenerated
- Rate limiting by Slack
- Firewall blocking outbound HTTPS to hooks.slack.com
- Proxy configuration required but not set

## How to Fix

### Docker Compose
Test connectivity from the container:

```bash
docker exec <notify-container> curl -v https://hooks.slack.com/
```

If behind a proxy:
```yaml
environment:
  HTTPS_PROXY: "http://proxy.example.com:8080"
```

### Bare Metal / systemd
```bash
curl -v https://hooks.slack.com/
curl -X POST -H 'Content-type: application/json' \
  --data '{"text":"Doctor test"}' \
  'https://hooks.slack.com/services/YOUR/WEBHOOK/URL'
```

### Kubernetes / Helm
```bash
kubectl exec -it <notify-pod> -- curl -v https://hooks.slack.com/
```

If the webhook URL has been revoked, create a new one in the Slack App settings under **Incoming Webhooks** and update the configuration.

## Verification
```
stella doctor run --check check.notify.slack.connectivity
```

## Related Checks
- `check.notify.slack.configured` — verifies Slack webhook URL is set
- `check.notify.queue.health` — verifies the notification delivery queue is healthy