Labels describe resources; selectors turn probe labels into execution placement. Keep those jobs separate when designing your taxonomy.
Create a label vocabulary
A label is a key/value pair with a maximum of 64 characters per part. Useful dimensions are stable and mutually understandable:
| Key | Example values |
|---|---|
region | taipei, tokyo, frankfurt |
provider | isp-a, cloud-b |
environment | production, staging, lab |
network | office, residential, mobile |
role | edge, datacenter, customer-site |
Create values under Labels, then attach them to probes and checks. Renaming or deleting a label can change selector outcomes, so inspect affected checks before a taxonomy change.
Select probes for a check
The controller uses a selector abstract syntax tree with label equality and logical composition. The web editor builds this expression and previews the active probes that match it.
Conceptually:
region=tokyo AND (provider=isp-a OR provider=isp-b)An empty selector matches every active project probe. Use that deliberately for global checks.
Effective assignments
For each matching enabled probe, the controller creates an effective probe/check assignment. The assignment records check and selector versions so agents can detect changes.
Assignments refresh after relevant probe, check, or label mutations. A background retry worker repairs refreshes that could not complete synchronously.
Troubleshoot missing results
Work in this order:
- Confirm the check is saved and its interval is valid.
- Preview the selector and confirm the expected probe appears.
- Confirm the probe is enabled.
- Confirm the probe is online and recently heartbeating.
- Inspect project assignments filtered by the probe or check.
- Wait for the agent’s assignment poll interval.
- Inspect probe service logs for executor or submission errors.
If a probe matches but cannot execute an explicit IPv4 or IPv6 check, inspect its reported IP-family capabilities and the host’s actual network configuration.
Keep public views intentional
Status pages can publish selected assignments or every assignment for a check. Review assignment membership after changing labels so a public page does not unexpectedly reveal a probe name, target, or location that was previously out of scope.