Anchor

Backup freshness monitor with ntfy alerts. Watches backup files and directories, alerts when they go stale or missing.

Zero dependencies. Single Python file, stdlib only. Docker-native.

Part of the Harbor self-hosted monitoring suite: Lookout (container lifecycle) · Beacon (status page) · Bosun (log alerts) · Sextant (TLS certs) · Drift (image updates) · Anchor (backup freshness)

Quick Start

services:
  anchor:
    image: ghcr.io/agent-cyanez/anchor
    volumes:
      - /path/to/backups:/backups:ro
    environment:
      BACKUP_TARGETS: "daily-db:/backups/db:24h,weekly-photos:/backups/photos:168h"
      NTFY_URL: http://ntfy:80
      NTFY_TOPIC: backups

How It Works

Anchor periodically checks the modification time of backup files and directories. If a backup hasn't been updated within its expected interval, Anchor sends an alert via ntfy.

• Files: Checks the file's modification time directly
• Directories: Finds the newest file recursively and checks its modification time
• Missing paths: Alerts immediately if the path doesn't exist

Configuration

Variable	Default	Description
BACKUP_TARGETS	(required)	Comma-separated targets: label:path:max_age
NTFY_URL	http://localhost:80	ntfy server URL
NTFY_TOPIC	backups	ntfy topic for alerts
NTFY_MAX_PRIORITY	(none)	Ceiling for alert priority (min, low, default, high, urgent). Set to default to keep high/urgent free for messages a human must see
CHECK_INTERVAL	3600	Seconds between checks
ALERT_COOLDOWN	86400	Seconds before re-alerting for same issue
HEALTH_PORT	8586	HTTP port for health/API endpoint

Target Format

Each target is label:path:max_age where:

• label — human-readable name (e.g. daily-db, weekly-photos)
• path — file or directory to check (must be mounted in the container)
• max_age — maximum acceptable age: 30m, 24h, 7d, or seconds

Examples

# Single daily database backup
BACKUP_TARGETS="postgres:/backups/db/latest.sql.gz:24h"

# Multiple schedules
BACKUP_TARGETS="db:/backups/db:24h,photos:/backups/photos:168h,config:/backups/config:48h"

# Hourly log archives
BACKUP_TARGETS="logs:/backups/logs:2h"

API

GET /health

Returns ok — for Docker healthcheck and Beacon integration.

GET /api/status

Returns JSON with current backup status:

{
  "targets": [
    {
      "label": "daily-db",
      "path": "/backups/db",
      "status": "fresh",
      "message": "backup is 3h 15m old",
      "max_age": 86400,
      "age": 11700
    }
  ],
  "checked_at": "2026-08-17T14:00:00Z"
}

Status values: fresh (within max_age), stale (exceeded max_age), missing (path not found).

License

MIT