A probe measures one component at a fixed interval. When a probe fails a number of times in a row, the state of the component changes to the state set on the probe. When the probe succeeds again, the component returns to operational. ## Kinds The following kinds of probes are available: - HTTP(S): requests an address and checks the status code and optionally a text in the answer. An HTTPS probe also checks that the certificate stays valid for at least the given number of days. - TCP: opens a connection to a host and port. - ICMP: sends a ping to a host. - DNS: resolves a name. - TLS: checks how long the certificate of a server stays valid. - TDS: runs a read-only query, such as `select 1`, on Microsoft SQL Server, encrypted with TLS. - Push: the component reports in itself on a fixed interval by calling its own address; silence for longer than allowed is a failure. This suits scheduled jobs. - Status page: reads the state of a component from the status page of another platform, in the format of Atlassian Statuspage, Crisp, Freshstatus or a custom page with a mapping. ## Rules The following rules apply to the probes of a tenant: - A probe of a tenant other than Invantive may only address a verified host name of the tenant itself or a known public service, such as Exact Online or AFAS Online. Private, loopback and link-local addresses are always refused, also through a redirect or a DNS name. - The shortest interval is 60 seconds. - Every poll counts against the polls per hour of the tenant. A probe that would exceed the limit is skipped and the refusal is recorded. - During a maintenance with muted probes, a failing probe leaves the component alone. Secrets of a probe, such as a password or a header value, are stored encrypted and are never shown again after saving. ## Automatic Incidents A probe can open an incident automatically when it fails, and close it when it recovers. When an incident for the component was closed less than 15 minutes ago, it is reopened instead of opening a new one, so a component that keeps failing and recovering does not open ten incidents. The answers of the failed polls are kept with the state change, so an operator can see what the probe saw.