Komga Monitoring with Vigilmon: Uptime, Health Checks & Library API Alerts for Your Comics Server

Your Komga server went down while you were mid-chapter. Your comic reader app throws a connection error. You have no idea if it's been down for five minutes or five hours — and your entire library of meticulously organized manga is completely unreachable.

Komga is a self-hosted media server for comics, manga, and digital books. It provides a polished web reader, OPDS catalog support, and a REST API compatible with popular reader apps like Tachiyomi and Kavita. Vigilmon gives you the external uptime monitoring that catches Komga failures before they ruin a reading session — covering health checks, web UI availability, API endpoints, and TLS certificate expiry.

This tutorial walks you through monitoring Komga end-to-end with Vigilmon.

What You'll Build

• A Vigilmon HTTP monitor on Komga's Spring Boot /actuator/health endpoint
• A web UI availability monitor
• A REST API library monitor
• SSL certificate expiry alerts
• Alert channels for immediate notification

Prerequisites

• A running Komga instance (typically on port 25600 behind a reverse proxy)
• A free account at vigilmon.online

Step 1: Monitor the /actuator/health Endpoint

Komga is built on Spring Boot, which ships with the Actuator health endpoint at /actuator/health. This endpoint returns a JSON payload describing the application status and its dependencies — including the database connection.

Test it from your terminal:

curl https://comics.yourdomain.com/actuator/health

Expected response:

{
  "status": "UP",
  "components": {
    "db": {"status": "UP"},
    "diskSpace": {"status": "UP"},
    "ping": {"status": "UP"}
  }
}

A status: UP response confirms that Komga is running, the H2 or SQLite database is accessible, and disk space is sufficient. Any component failure (database unreachable, disk full) will flip the top-level status to DOWN or OUT_OF_SERVICE.

Set up the Vigilmon monitor:

1. Log in to Vigilmon and click New Monitor → HTTP.
2. Set URL to https://comics.yourdomain.com/actuator/health.
3. Set Check interval to 60 seconds.
4. Set Expected status code to 200.
5. Under Advanced → JSON body assertion, add:
   • Path: status
   • Operator: equals
   • Value: UP
6. Save the monitor.

Vigilmon now verifies Komga's full health stack every minute from multiple regions.

Note: By default, Komga's actuator health endpoint is publicly accessible. If you've locked it down with Spring Security, create a dedicated monitoring user or allowlist the Vigilmon probe IP ranges.

Step 2: Monitor Web UI Availability

The actuator endpoint checks Spring Boot internals, but not the web frontend that users navigate. A broken static asset deployment, a JavaScript error, or a misconfigured reverse proxy path can leave the health endpoint green while users see a blank page.

Add a keyword monitor on the Komga web UI:

1. Click New Monitor → HTTP in Vigilmon.
2. Set URL to https://comics.yourdomain.com/ (your Komga homepage).
3. Set Expected status code to 200.
4. Under Advanced → Keyword check, configure:
   • Keyword present: Komga
5. Save.

The Komga web UI HTML includes the application name in the page title and app metadata. If the UI fails to load, the keyword check fires.

Step 3: Monitor the REST API

Komga's REST API powers both the web UI and third-party apps (Tachiyomi, Chunky, Panels). A database migration failure or a permission misconfiguration can break the API while the health endpoint stays green.

Monitor the libraries API endpoint — it's lightweight and exercises the full request pipeline:

1. Click New Monitor → HTTP in Vigilmon.
2. Set URL to https://comics.yourdomain.com/api/v1/libraries.
3. Under Advanced → Authentication, set Basic Auth with your Komga credentials (or create a dedicated monitoring user in Komga's user management).
4. Set Expected status code to 200.
5. Under Advanced → Keyword check:
   • Keyword present: libraryCount or your library name
6. Save.

A successful response lists your configured libraries. If the API breaks — for example, after an upgrade that changes the schema — this monitor catches it while your /actuator/health stays green.

Step 4: SSL Certificate Monitoring

Komga is typically served over HTTPS via Nginx, Caddy, or a reverse proxy container. An expired TLS certificate will lock out every client — reader apps included — with no obvious error message to non-technical family members or co-users.

Vigilmon monitors SSL certificate validity automatically for every HTTPS monitor. To configure expiry alerts:

1. Open any of your HTTPS Komga monitors in Vigilmon.
2. Go to Settings → SSL.
3. Enable Alert when certificate expires within 14 days.
4. Optionally enable Alert when certificate expires within 30 days for early warning.

Sample alert:

⚠️  SSL Warning: comics.yourdomain.com
Certificate expires in 11 days (2026-07-12)
Renew via: Let's Encrypt / Certbot / Caddy ACME

Step 5: Alert Channels

Go to Notifications → New Channel in Vigilmon and configure your preferred delivery method:

• Email — immediate alerts to your inbox
• Webhook — push to Discord, Slack, or ntfy.sh for mobile push notifications

For a home server Discord channel, paste your webhook URL. A Komga downtime alert looks like:

🔴 DOWN: comics.yourdomain.com/actuator/health
Komga health check failed — status not UP
Region: US-East
Triggered: 2026-01-22 01:47 UTC

Recovery:

✅ RECOVERED: comics.yourdomain.com/actuator/health
Downtime: 14 minutes

Step 6: Status Page

Go to Status Pages → New Status Page in Vigilmon. Add your Komga monitors and publish. Share the link with family or household members so they can self-check status before messaging you.

What You've Built

| Scenario | How Vigilmon catches it | |---|---| | Komga process crash | /actuator/health returns non-200 | | Database (H2/SQLite) unreachable | Health endpoint db component flips to DOWN | | Disk space exhausted | Health endpoint diskSpace component flips to DOWN | | Reverse proxy (Nginx/Caddy) down | HTTPS monitor detects 502 or connection refused | | Web UI assets broken | Keyword monitor on homepage fails | | REST API broken after upgrade | Library API endpoint returns non-200 | | SSL certificate expired or expiring | SSL expiry alert triggers |

Self-hosting Komga means your library is yours — no subscriptions, no cloud dependency. But it also means you're the ops team. Vigilmon gives you the external monitoring layer that catches failures before they interrupt reading.

Start monitoring your Komga server today — register free at vigilmon.online.