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. After you click Test URL, basic assertions on response time and available records are added. You must define at least one assertion for your test to monitor.

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

To perform OR logic in an assertion, use the matches regex comparator to define a regex with multiple expected values for the same assertion type like (0|100). The test result is successful if every available record or at least one record assertions’ value is 0 or 100.

If a test does not contain an assertion on the response body, the body payload drops and returns an associated response time for the request within the timeout limit set by the Synthetics Worker.

If a test contains an assertion on the response body and the timeout limit is reached, an Assertions on the body/response cannot be run beyond this limit error appears.

Select locations

Select the Locations to run your DNS test from. DNS tests can run from both managed and private locations depending on your preference for monitoring a public or private domain.

Datadog’s out-of-the-box managed locations allow you to test public-facing websites and endpoints from regions where your customers are located.

The Datadog for Government site (US1-FED) uses the following managed location:

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 your test 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.

Configure the test monitor

A notification is sent by your test based on the alerting conditions previously defined. Use this section to define how and what to message 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 dropdown 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 an alert.
   {{^is_recovery}}	Show unless the test recovers from an alert.
   {{#is_renotify}}	Show when the monitor renotifies.
   {{^is_renotify}}	Show unless the monitor renotifies.
   {{#is_priority}}	Show when the monitor matches priority (P1 to P5).
   {{^is_priority}}	Show unless the monitor matches priority (P1 to P5).

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.

4. Click Create to save your test configuration and monitor.

For more information, see Using Synthetic Test Monitors.

Variables

Create local variables

To create a local variable, click Create a Local Variable. You can select one of the following available builtins to add to your variable string:

{{ 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.

{{ uuid }}

Generates a version 4 universally unique identifier (UUID).

{{ date(n unit, format) }}

Generates a date in one of Datadog’s accepted formats with a value corresponding to the UTC date the test is initiated at + or - n units.

{{ timestamp(n, unit) }}

Generates a timestamp in one of Datadog’s accepted units with a value corresponding to the UTC timestamp the test is initiated at +/- n units.

To obfuscate local variable values in test results, select Hide and obfuscate variable value. Once you have defined the variable string, click Add Variable.

Use variables

You can use the global variables defined on the Settings page in the URL, advanced options, and assertions of your DNS 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 are using the custom role feature, add your user to any custom role that includes synthetics_read and synthetics_write permissions.

Restrict access

Access restriction is available for customers using custom roles on their accounts.

You can restrict access to a DNS test based on the roles in your organization. When creating a DNS test, choose which roles (in addition to your user) can read and write your test.

Further Reading

Additional helpful documentation, links, and articles:

Introducing Datadog Synthetic MonitoringBLOG DNS monitoring with DatadogBLOG Get started with API testsDOCUMENTATION Test DNS resolution of your internal endpointsDOCUMENTATION Learn about Synthetic test monitorsDOCUMENTATION