Configure DNS probes

DNS probes resolve a domain through the agent's DNS resolver and report the resolution time in milliseconds. Optional value-match verifies the answer.

Configuration shape

{
  "domain": "api.example.com",
  "record_type": "A",
  "expected_value": "203.0.113.10",
  "resolver": "1.1.1.1"
}

Field reference

Field	Default	Notes
`domain`	required	The domain to resolve.
`record_type`	`A`	One of `A`, `AAAA`, `CNAME`, `MX`, `TXT`, `NS`, `SRV`, `CAA`, `PTR`.
`expected_value`	none	Optional substring match against the resolved record. Mismatch reports `expected_value_mismatch`.
`resolver`	system default	Optional override resolver IP. Useful for verifying a specific authoritative server.

Reason codes

The reason field surfaces standard Node DNS error codes:

Reason	Meaning
`ENOTFOUND`	The domain does not resolve.
`ETIMEDOUT`	The resolver did not answer in time.
`ESERVFAIL`	The resolver returned `SERVFAIL`.
`expected_value_mismatch`	Resolution succeeded but the record did not contain `expected_value`.
`dns_error`	Other resolver error.

Threshold examples

Goal	Healthy	Unhealthy
Authoritative answer fast	`under 50`	`over 500`
Resolution succeeds at all	`under 5000`	`over 10000`

When the test is purely "does the domain still resolve", unhealthy_value set to a timeout-equivalent threshold combined with no_data on ENOTFOUND covers the case.