FabledSteward/docs/core/alerting.md

Alerting

Alert rules evaluate every metric that flows through record_metric(). There is no separate polling process — evaluation is inline with every metric write.

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How It Works

When any monitor or plugin calls record_metric():

1. The metric value is written to the plugin_metrics table, and plugin_metric_latest moves to it if it is the newest sample of that metric
2. All enabled AlertRule rows matching (source_module, resource_name, metric_name) are loaded
3. Each matching rule is evaluated against the new value
4. If a state transition occurs, an AlertEvent row is written
5. Notification I/O is deferred outside the transaction via asyncio.create_task()

Key function: steward/core/alerts.py → record_metric(session, source_module, resource_name, metric_name, value)

record_metric() must always be called inside an active transaction:

async with session.begin():
    await record_metric(session, "ping", "my-server", "response_time_ms", 42.3)

Notifications are sent via asyncio.create_task() after the function returns, so no network I/O blocks the DB transaction.

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Alert State Machine

Each AlertRule has one associated AlertState row. The state transitions are:

inactive ──(breached)──► pending ──(consecutive count met)──► FIRING
                │                                               │
                └──(recovered)──► inactive (no notification)   │
                                                               │
                                          FIRING ──(recovered)──► RESOLVED ──► inactive
                                          FIRING ──(acknowledged)──► ACKNOWLEDGED
                                          ACKNOWLEDGED ──(recovered)──► RESOLVED ──► inactive
                                          ACKNOWLEDGED ──(re-breached)──► FIRING

RESOLVED is transient — the evaluator writes the event and immediately sets state back to inactive within the same transaction. RESOLVED never persists as a final state in the DB.

State Definitions

State	Meaning
inactive	Threshold not breached
pending	Threshold breached but consecutive count not yet met; no notification sent
firing	Consecutive count met; FIRING notification sent
acknowledged	Operator acknowledged; suppresses repeat notifications; auto-clears on recovery
resolved	Transient — notification sent, immediately transitions to inactive

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Creating Alert Rules

Alert rules are created in the UI at /alerts/. Each rule requires:

• Name — human-readable label
• Source module — ping, dns, traefik, or any plugin name
• Resource name — host name, router name, etc. (must match exactly what the monitor writes)
• Metric name — the metric key (e.g. response_time_ms, up, error_rate_5xx_pct)
• Operator — >, <, >=, <=, ==, !=
• Threshold — numeric value
• Consecutive failures required — how many consecutive breaches before FIRING (default 1)

Available Metrics by Module

source_module	metric_name	Description
ping	response_time_ms	Probe latency (0.0 if down)
ping	up	1.0 = up, 0.0 = down
dns	resolved	1.0 = resolved, 0.0 = failed
dns	ip_changed	1.0 = IP changed from previous result
traefik	request_rate	Requests per second
traefik	error_rate_4xx_pct	4xx errors as % of requests
traefik	error_rate_5xx_pct	5xx errors as % of requests
traefik	latency_p50_ms	Approximate p50 latency (ms)
traefik	latency_p95_ms	Approximate p95 latency (ms)
traefik	latency_p99_ms	Approximate p99 latency (ms)

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Notifications

Notifications fire on FIRING and RESOLVED transitions. All configured channels receive every notification; there is no per-rule channel routing.

Email

Configured at /settings/ under SMTP. Settings:

Setting key	Description
smtp.host	SMTP server
smtp.port	Port (default 587)
smtp.tls	STARTTLS (default true)
smtp.username	Login
smtp.password	Password
smtp.recipients	List of email addresses

Email is skipped if smtp.host is empty.

Webhook

Configured at /settings/ under Webhook. The body is a Jinja2 template rendered to JSON. Content-Type is always application/json. If the rendered template is not valid JSON, the delivery is logged as failed and no request is sent.

Template variable	Type	Description
alert.rule_name	str	Alert rule name
alert.state	str	FIRING or RESOLVED
alert.metric	str	Metric name
alert.value	float	Current value
alert.threshold	float	Configured threshold
alert.resource	str	Resource name
alert.source_module	str	ping, dns, traefik, etc.
alert.timestamp	str	ISO 8601 UTC

Default template (Discord-compatible):

{"content": "**{{ alert.state }}** — {{ alert.resource }} — {{ alert.rule_name }} ({{ alert.metric }} = {{ alert.value }})"}

Webhook is skipped if webhook.url is empty.

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Data Models

Defined in steward/models/alerts.py:

• alert_rules — one row per configured rule
• alert_states — one row per rule, tracks current state and consecutive failure count
• alert_events — append-only log of all state transitions and notification outcomes
• plugin_metrics — all metric values written by any monitor or plugin
• plugin_metric_latest — the newest sample of each (source, resource, metric). Pages that show "what it is now" read this instead of searching history; retention drops a row once its sample leaves the raw window