DNS Monitor Reference

A DNS monitor verifies the availability and correctness of DNS records. It performs periodic lookups for specified DNS record types against a target domain or subdomain from various geographical locations.

Use cases:

Validating domain name resolution.
Monitoring changes to critical DNS records (e.g., A, CNAME, MX).
Ensuring proper load balancing via DNS (when combined with multi-region checks).
Detecting unauthorised DNS alterations.

Configuration

URI

Type: String (required) Format: Domain name or subdomain

The fully qualified domain name or subdomain to be monitored.

Examples:

openstat.us
api.example.com
mail.example.org

Record types

The monitor supports fetching and validating the following DNS record types:

A (address record) — maps a domain name to an IPv4 address.
AAAA (IPv6 address record) — maps a domain name to an IPv6 address.
CNAME (canonical name record) — maps an alias domain name to another canonical domain name.
MX (mail exchange record) — specifies the mail servers responsible for accepting email messages on behalf of a domain name.
NS (name server record) — delegates a domain or subdomain to a set of authoritative name servers.
TXT (text record) — carries arbitrary human-readable text and is also used for purposes like SPF, DKIM, DMARC, and site verification.

Regions

The geographical locations from which the DNS monitoring checks are performed. This allows for verification of DNS propagation and performance across different networks. See the Location Reference for the full list of regions and the IPs to allowlist.

Frequency

The interval at which the DNS checks are performed. Supported frequencies:

30 seconds
1 minute
5 minutes
10 minutes
30 minutes
1 hour

Response time thresholds

Timeout

Type: Duration (optional) Default: 45 seconds

The maximum duration to wait for a DNS response. If the lookup exceeds this time, the check is considered failed.

Degraded

Type: Duration (optional)

The duration after which a DNS response is considered degraded. This indicates a performance issue without being a complete failure.

Retry

Type: Integer (optional) Default: 3

The number of times the monitor will retry a failed DNS lookup before reporting a definitive failure. For example: 3

Assertions

Assertions let you validate the records returned by a DNS lookup. A check fails if any assertion does not match.

Limits: up to 10 assertions per monitor.

Record assertions

Validate the values returned for a specific DNS record type.

Supported record types: A, AAAA, CNAME, MX, TXT.

NS records can be looked up but cannot be asserted on.

Comparisons:

Equal — the returned record value must exactly match the specified target.
Not Equal — the returned record value must not exactly match the specified target.
Contains — the returned record value must include the specified target string.
Not Contains — the returned record value must not include the specified target string.

Example use cases:

Verify an A record resolves to your expected IP after a DNS change.
Confirm a CNAME still points at your CDN provider.
Check that an MX record contains the expected mail host.
Detect drift in TXT records (SPF, DKIM, DMARC, site verification).

OpenTelemetry

Configures the export of monitoring metrics to an OpenTelemetry-compatible observability platform.

OTLP endpoint

Type: String (optional) Protocol: HTTP only

The OTLP (OpenTelemetry Protocol) endpoint URL where collected metrics should be exported.

Example: https://otlp.example.com/v1/metrics

OTLP headers

Type: Key-value pairs (optional)

Custom headers to include when sending metrics to your OTLP endpoint. Commonly used for authentication or tenant identification.

Common example:

Authorization: Bearer <your_token>

CLI reference — manage monitors as code using the openstatus CLI.