Alerting

UpSlim sends alerts through providers. Each provider is defined once in the alerting section and referenced by name from individual monitors.

Provider configuration

alerting:
  - name: slack-ops          # reference name used in monitors
    type: slack
    token: ${SLACK_BOT_TOKEN}
    channel: "#ops-alerts"
    reminder_interval: 2h    # optional: resend while still down

How the state machine works

UpSlim does not alert on every failed check. It tracks a state per (monitor, provider) pair and transitions between states based on thresholds.

          failure_threshold reached
Healthy ─────────────────────────────► Firing
           (sends DOWN alert)

           success_threshold reached
Firing  ─────────────────────────────► Recovered
           (sends RECOVERED alert, if send_on_resolved: true)

           (resets to Healthy)

Firing

A check must fail consecutively failure_threshold times (default: 3) before the first alert is sent. This prevents flapping from causing alert noise.

Recovery

A check must pass consecutively success_threshold times (default: 2) before a recovery alert is sent. This prevents a single transient success from triggering a false recovery.

Reminders

If reminder_interval is set on a provider, UpSlim resends the alert while the monitor stays down:

alerting:
  - name: slack-ops
    type: slack
    token: ${SLACK_BOT_TOKEN}
    channel: "#ops-alerts"
    reminder_interval: 2h   # resend every 2 hours while still DOWN

Remove reminder_interval entirely if you only want one alert per incident.

Alert payload

Each alert contains:

• Monitor name
• URL (HTTP monitors)
• Timestamp
• Response time
• Status code (HTTP monitors)
• Failure reason — the condition that failed, e.g. [STATUS] == 200: got '503'

Supported providers

Provider	Status
Slack	✅ Available
PagerDuty	Planned
Email	Planned
Webhook	Planned

Using multiple providers

A monitor can send to multiple providers simultaneously:

alerting:
  - name: slack-team
    type: slack
    token: ${SLACK_TOKEN}
    channel: "#alerts"

  - name: slack-oncall
    type: slack
    token: ${SLACK_TOKEN}
    channel: "#oncall"

monitors:
  - name: payments
    type: http
    url: "https://payments.example.com/health"
    conditions:
      - "[STATUS] == 200"
    alerts:
      - name: slack-team
      - name: slack-oncall    # both providers notified