DNS

DNS monitors verify that a hostname resolves for a specific record type and (optionally) that the returned values match what you expect.

How a check works

Telescope resolves the hostname from monitor target (or URL hostname fallback).
It loads DNS config (recordType, optional nameserver, optional expected values).
If nameserver is configured, Telescope queries that resolver directly.
The worker requests the configured record type (A, AAAA, CNAME, MX, TXT, NS, SOA) with a bounded timeout.
Returned records are normalized into a stable RRset representation (deduped, order-insensitive for matching).
If expected values are configured, Telescope compares expected values against normalized DNS results.

Condition	Status	What it means
Records resolve and expected values match (or no expected values configured)	Up	DNS is healthy for the requested record type
Records resolve but expected values do not match	Down	DNS answer changed or is misconfigured
Query timeout / NXDOMAIN / NODATA / resolver failure	Down	DNS lookup failed for this check

DNS monitor checks currently use up/down states (no degraded state).

Setting	Default	Description
`recordType`	`A`	DNS record type to query
`expectedValue`	unset	Legacy single expected value alias
`expectedValues`	unset	One or more expected values to match
`nameserver`	system resolver	Optional resolver override (e.g. `1.1.1.1`)
`timeout`	monitor timeout	Optional DNS query timeout override (250ms-30000ms)

DNS checks store structured data in result_data, including:

TXT expected-value matching supports substring checks (useful for SPF/DMARC prefixes).
MX expected values can match either full priority exchange entries or exchange hostnames.
If no nameserver is set, worker host DNS configuration is used.