How Licensing Works
Overview
ACS Monitor uses a server-based licensing model. Each ACS Monitor instance you deploy requires its own license key, which determines your tier and the maximum number of devices and service monitors you can configure. The licensing system is designed to be simple, transparent, and non-intrusive to your monitoring operations.
License Keys
When you register a server on this platform, a unique 32-character hexadecimal license key is generated and assigned to that server. This key is:
- Cryptographically random — generated using a secure random number generator
- Unique per server — each ACS Monitor instance has its own key
- Embedded during installation — the key is permanently configured in your instance during the install process
- Used for all API communication — your instance uses this key to authenticate with the licensing server
For more details about key management, see the License Keys page.
Device and Monitor Caps
Each licensing tier has a combined cap for devices and service monitors. Devices and service monitors are counted together toward your total. For example, if you are on the Free tier with a cap of 100:
- 60 devices + 40 service monitors = 100 total (at cap)
- 100 devices + 0 service monitors = 100 total (at cap)
- 30 devices + 50 service monitors = 80 total (under cap)
A "device" is any host being monitored (server, switch, router, access point, etc.). A "service monitor" is an individual check that is not tied to a specific device, such as monitoring an external URL or DNS resolution.
What Happens at the Cap
When your combined device and monitor count reaches your tier's cap:
- You will not be able to add new devices or service monitors
- All existing monitoring continues without interruption
- You will see a warning in your ACS Monitor dashboard indicating you are at capacity
- The licensing server will return a cap-reached status in heartbeat responses
To add more devices or monitors, you can either remove existing ones or upgrade to a higher tier.
The Heartbeat System
Your ACS Monitor instance periodically sends heartbeat reports to this licensing server. Each heartbeat includes:
- Current device count and service monitor count
- Application version
- Host OS name and version
- Resource usage (CPU, memory, disk)
Heartbeats serve multiple purposes:
- License validation — confirms your license is still active and valid
- Usage tracking — ensures you are within your tier's cap
- Health monitoring — allows you to check your server's status from this dashboard
- Version tracking — helps identify servers that need updates
If a heartbeat is not received within the configured threshold (default 10 minutes), your server will show as "offline" in the licensing dashboard. This is purely informational — your ACS Monitor instance continues to function normally regardless of heartbeat status.
For more details about the heartbeat system, see Heartbeat Monitoring.
Tamper Protection
The licensing system includes protections against tampering and abuse:
- License keys are validated server-side on every heartbeat
- Device and monitor counts are verified against your tier's cap
- Suspended or expired licenses will prevent the addition of new devices and monitors
- The licensing server can flag accounts or servers for review if unusual patterns are detected
Offline Operation
ACS Monitor is designed to be resilient. If your instance cannot reach the licensing server temporarily (network issues, maintenance, etc.), all existing monitoring continues to function. The license is cached locally, and heartbeats will resume automatically when connectivity is restored.