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Slack Notifications

The RCB platform sends two types of notifications to Slack:

  1. Deploy notifications — sent by GitHub Actions on deploy success or failure
  2. Infrastructure alerts — sent by Prometheus Alertmanager when service is down / degraded

Both use the same Slack channel (#rcb-alerts) and the same webhook URL (SLACK_WEBHOOK_URL).

Notification Flow​

Step 1 — Create a Slack App & Incoming Webhook​

  1. Go to api.slack.com/apps → Create New App → From scratch
  2. Name: RCB Alertmanager, workspace: your Slack workspace
  3. In the left sidebar → Incoming Webhooks → toggle Activate Incoming Webhooks ON
  4. Click Add New Webhook to Workspace
  5. Select the channel #rcb-alerts (create it first if it doesn't exist)
  6. Click Allow
  7. Copy the webhook URL — it looks like: 
    https://hooks.slack.com/services/T.../B.../...
Keep this URL secret

The webhook URL grants anyone the ability to post to your Slack channel. Never commit it to git.

Step 2 — Add to VPS .env​

# /opt/rcb/.env
SLACK_WEBHOOK_URL=https://hooks.slack.com/services/T.../B.../...

Step 3 — Regenerate Alertmanager Config​

After setting SLACK_WEBHOOK_URL in .env, regenerate the Alertmanager config:

export SLACK_WEBHOOK_URL=$(grep '^SLACK_WEBHOOK_URL=' /opt/rcb/.env | cut -d'=' -f2)

envsubst < /opt/rcb/infra/local/observability/alertmanager/alertmanager.yml.template \
  > /opt/rcb/infra/local/observability/alertmanager/alertmanager.yml

# Reload Alertmanager
docker exec rcb_alertmanager kill -HUP 1

Step 4 — Add to GitHub Actions Secrets​

Add SLACK_WEBHOOK_URL as a repository secret in both repos:

  • ivelin1936/Renault-Club-Bulgaria → Settings → Secrets → Actions
  • ivelin1936/renault-club-bulgaria-fe → Settings → Secrets → Actions

Step 5 — Test the Webhook​

# Test directly
curl -X POST -H 'Content-type: application/json' \
  --data '{"text":"✅ RCB webhook test — if you see this, Slack is configured correctly"}' \
  $SLACK_WEBHOOK_URL

Expected: message appears in #rcb-alerts.

Message Examples​

GitHub Actions — Deploy Success​

✅ *RCB Backend deployed successfully*
• Tag: `sha-abc1234`
• Branch: `future`
• View run → https://github.com/.../actions/runs/...

GitHub Actions — Deploy Failure​

🔴 *RCB Backend deploy FAILED*
• Branch: `future`
• Tag: `sha-abc1234`
• View failed run → https://github.com/.../actions/runs/...

Alertmanager — Firing Alert​

🔴 RCB Alert: ServiceDown

*Summary:* RCB service rcb-backend is unreachable
*Details:* Prometheus cannot scrape rcb-backend at rcb-backend:8080.
           The service may be down or its health endpoint is failing.
           Check VPS: make status
*Severity:* critical

Alertmanager — Resolved Alert​

✅ RCB Alert: ServiceDown

*Summary:* RCB service rcb-backend is unreachable
*Details:* ...
*Severity:* critical

GitHub Actions Notification Configuration​

The slackapi/slack-github-action@v2.0.0 action is used in both BE and FE pipelines:

- name: Notify Slack — Deploy Success
  if: success()
  uses: slackapi/slack-github-action@v2.0.0
  with:
    webhook: ${{ secrets.SLACK_WEBHOOK_URL }}
    webhook-type: incoming-webhook
    payload: |
      {
        "text": "✅ *RCB Backend deployed successfully*\n• Tag: `sha-${{ needs.docker.outputs.image_sha }}`\n• Branch: `future`\n• <${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}|View run>"
      }

- name: Notify Slack — Deploy Failure
  if: failure()
  uses: slackapi/slack-github-action@v2.0.0
  with:
    webhook: ${{ secrets.SLACK_WEBHOOK_URL }}
    webhook-type: incoming-webhook
    payload: |
      {
        "text": "🔴 *RCB Backend deploy FAILED*\n• Branch: `future`\n• Tag: `sha-${{ needs.docker.outputs.image_sha }}`\n• <${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}|View failed run>"
      }

if: success() and if: failure() evaluate the entire job status — not just the previous step.

Alertmanager Notification Configuration​

The Alertmanager Slack config (from alertmanager.yml.template):

receivers:
  - name: 'slack-rcb'
    slack_configs:
      - api_url: '${SLACK_WEBHOOK_URL}'
        channel: '#rcb-alerts'
        send_resolved: true          # also notify when alert resolves
        title: '{{ if eq .Status "firing" }}🔴{{ else }}✅{{ end }} RCB Alert: {{ .GroupLabels.alertname }}'
        text: |
          {{ range .Alerts }}
          *Summary:* {{ .Annotations.summary }}
          *Details:* {{ .Annotations.description }}
          *Severity:* {{ .Labels.severity }}
          {{ end }}
        icon_emoji: ':rotating_light:'
        username: 'RCB Alertmanager'

Key settings:

  • send_resolved: true — sends a green ✅ message when the issue clears
  • group_by: ['alertname', 'job'] — groups related alerts into one Slack message
  • repeat_interval: 4h — re-notifies if alert is still firing after 4 hours

Troubleshooting​

SymptomFix
No messages in SlackVerify SLACK_WEBHOOK_URL with the curl test above
channel_not_found errorCreate #rcb-alerts channel in Slack, then re-add webhook
Alerts not sent but webhook worksCheck Prometheus → Alertmanager connection: curl http://localhost:9093/api/v2/status
Duplicate alert messagesCheck group_interval and repeat_interval in alertmanager.yml
Old webhook URL (rotated)Update .env, re-run envsubst, reload Alertmanager, update GitHub secret