Alerts & notifications

Pier watches host and container metrics, plus lifecycle events like deploys and backups, and sends notifications when something crosses a threshold or fails.

Alert rules

A rule pairs a metric with a threshold, a comparison and a severity. Numeric rules are evaluated on a recurring tick (default every 30 seconds); event rules fire from the code path that produced the event.

Available metrics:

Group	Metrics
Host	cpu, ram, disk
Container	container_cpu, container_ram, container_status, container_restarts
Lifecycle	deploy_status, deploy_success, backup_status, backup_success
Infra	agent_offline, server_reachable, ssl_expiry, docker_cleanup_success, docker_cleanup_failure

Each rule also carries:

• comparison — gt, lt or eq.
• severity — info, warning or critical.
• scope — global or a specific service.
• duration — how long a breach must hold before firing (default 60s).
• cooldown — minimum gap between repeat fires while still breached (default 30 minutes).

A rule fires once its breach has held for the configured duration, re-fires only after the cooldown elapses, and automatically resolves when the value returns under threshold.

Notification channels

Pier ships four channels. Each has one global configuration, stored encrypted:

Channel	Configuration
Telegram	Bot token + chat ID
Email	Driver (smtp, brevo or resend) + from/to addresses
Discord	Webhook URL + optional @here ping
Slack	Webhook URL

For SMTP email, the encryption mode (starttls, tls, none), host, port (default 587) and credentials are configured per channel. Brevo and Resend send through their HTTP APIs with an API key instead.

Telegram delivery hits api.telegram.org directly. If your server’s network blocks that host, Telegram notifications will fail to send even though the configuration is valid.

Test notifications

Each channel has a Test action that sends a sample message through the live configuration, so you can confirm credentials and connectivity before relying on the channel. Individual rules can also send a test message tagged [TEST].

The event feed

Every fire and resolve is recorded as an event with its delivery status. Two views are available:

• A global feed of the most recent events across all rules.
• A per-rule history of that rule’s recent events.

Failed deliveries are kept with the error message attached, so a misconfigured webhook or bad SMTP host is visible in the feed rather than silently dropped.

Preset alerts

Pier seeds a set of ready-made preset rules so you don’t start from a blank slate. Presets are toggled on or off rather than built field-by-field, and they deliver through the global channel configuration above instead of carrying their own credentials.

Next steps

• System maintenance — Docker cleanup events feed alerts too.
• Backups — back up databases the alerts watch over.
• Troubleshooting — when notifications don’t arrive.