DNS Tests

DNS Tests

Overview

DNS tests allow you to proactively monitor the resolvability and lookup times of your DNS records using any nameserver. If resolution is unexpectedly slow or a DNS server answers with unexpected A, AAAA, CNAME, TXT, or MX entries, Datadog sends you an alert with details on the failure, allowing you to quickly pinpoint the root cause of the issue and fix it.

DNS tests can run from both managed and private locations depending on your preference for running the test from outside or inside your network. DNS tests can run on a schedule, on-demand, or directly within your CI/CD pipelines.

Configuration

After choosing to create a DNS test, define your test’s request.

Define request

  1. Specify the Domain you want your test to query. For example, www.example.com.
  2. Specify the DNS Server to use (optional), it can be a domain name or an IP address. If not specified, your DNS test performs resolution using 8.8.8.8, with a fallback on 1.1.1.1 and an internal AWS DNS server.
  3. Specify your DNS Server Port (optional). If not specified, the DNS Server port defaults to 53.
  4. Specify the amount of time in seconds before the test times out (optional).
  5. Name your DNS test.
  6. Add env Tags as well as any other tag to your DNS test. You can then use these tags to quickly filter through your Synthetic tests on the Synthetic Monitoring homepage.

Click Test URL to try out the request configuration. A response preview is displayed on the right side of your screen.

Define assertions

Assertions define what an expected test result is. When hitting Test URL basic assertions on response time and available records are added. You must define at least one assertion for your test to monitor.

Type Record type Operator Value type
response time is less than Integer (ms)
every record of type A, of type AAAA, of type MX, of type TXT, of type CNAME is, contains,
matches, does not match
String
Regex
at least one record of type A, of type AAAA, of type MX, of type TXT, of type CNAME is, contains,
matches, does not match
String
Regex

You can create up to 20 assertions per API test by clicking on New Assertion or by clicking directly on the response preview:

Select locations

Select the Locations to run your DNS test from: DNS tests can run from managed and private locations depending on whether you are willing to monitor a public or a private domain.

Specify test frequency

DNS tests can run:

  • On a schedule to ensure your most important services are always accessible to your users. Select the frequency at which you want Datadog to run your DNS test.
  • Within your CI/CD pipelines.
  • On-demand to run your tests whenever makes the most sense for your team.

Define alert conditions

Set alert conditions to determine the circumstances under which you want a test to fail and trigger an alert.

Alerting rule

When you set the alert conditions to: An alert is triggered if any assertion fails for X minutes from any n of N locations, an alert is triggered only if these two conditions are true:

  • At least one location was in failure (at least one assertion failed) during the last X minutes;
  • At one moment during the last X minutes, at least n locations were in failure.

Fast retry

Your test can trigger retries X times after Y ms in case of a failed test result. Customize the retry interval to suit your alerting sensibility.

Location uptime is computed on a per-evaluation basis (whether the last test result before evaluation was up or down). The total uptime is computed based on the configured alert conditions. Notifications sent are based on the total uptime.

Notify your team

A notification is sent by your test based on the alerting conditions previously defined. Use this section to define how and what message to send to your teams.

  1. Similar to how you configure monitors, select users and/or services that should receive notifications either by adding a @notificationto the message or by searching for team members and connected integrations with the drop-down box.

  2. Enter the notification message for your test. This field allows standard Markdown formatting and supports the following conditional variables:

    Conditional Variable Description
    {{#is_alert}} Show when the test alerts.
    {{^is_alert}} Show unless the test alerts.
    {{#is_recovery}} Show when the test recovers from alert.
    {{^is_recovery}} Show unless the test recovers from alert.
  3. Specify how often you want your test to re-send the notification message in case of test failure. To prevent renotification on failing tests, leave the option as Never renotify if the monitor has not been resolved.

Click on Save to save your test and have Datadog start executing it.

Variables

Create local variables

You can create local variables by clicking on Create Local Variable at the top right hand corner of your test configuration form. You can define their values from one of the below available builtins:

{{ numeric(n) }}
Generates a numeric string with n digits.
{{ alphabetic(n) }}
Generates an alphabetic string with n letters.
{{ alphanumeric(n) }}
Generates an alphanumeric string with n characters.
{{ date(n, format) }}
Generates a date in one of our accepted formats with a value of the date the test is initiated + n days.
{{ timestamp(n, unit) }}
Generates a timestamp in one of our accepted units with a value of the timestamp the test is initiated at +/- n chosen unit.

Use variables

You can use the global variables defined in the Settings and the locally defined variables in the URL, advanced options, and assertions of your HTTP tests.

To display your list of variables, type {{ in your desired field:

Test failure

A test is considered FAILED if it does not satisfy one or more assertions or if the request prematurely failed. In some cases, the test can fail without testing the assertions against the endpoint.

These reasons include the following:

CONNRESET
The connection was abruptly closed by the remote server. Possible causes include the web server encountering an error or crashing while responding, or loss of connectivity of the web server.
DNS
DNS entry not found for the test URL. Possible causes include misconfigured test URL or the wrong configuration of your DNS entries.
INVALID_REQUEST
The configuration of the test is invalid (for example, a typo in the URL).
TIMEOUT
The request couldn’t be completed in a reasonable time. Two types of TIMEOUT can happen:
  • TIMEOUT: The request couldn’t be completed in a reasonable time. indicates that the request duration hit the test defined timeout (default is set to 60s). For each request only the completed stages for the request are displayed in the network waterfall. For example, in the case of Total response time only being displayed, the timeout occurred during the DNS resolution.
  • TIMEOUT: Overall test execution couldn't be completed in a reasonable time. indicates that the test duration (request + assertions) hits the maximum duration (60.5s).

Permissions

By default, only users with the Datadog Admin and Datadog Standard roles can create, edit, and delete Synthetic DNS tests. To get create, edit, and delete access to Synthetic DNS tests, upgrade your user to one of those two default roles.

If you have access to the custom role feature, add your user to any custom role that includes synthetics_read and synthetics_write permissions.

Further Reading