Summary
Applications monitored by RUM generate JavaScript errors referring after New RUM Experience is enabled. This is caused by the RUM JavaScript Agent interacting with code that implements as standard browser API incorrectly in other JavaScript on the page.
Problem
After enabling the New Real User Monitoring Experience, some customers have reported encountering JavaScript errors on pages that worked before the new experience was activated. We are seeing errors arise when the front-end code using common browser APIs that return an invalid value, i.e. a value that does not satisfy the testing function.
The RUM JavaScript Agent uses many common Browser APIs that may also be used by JavaScript code in use elsewhere on the page. In order for full compatibility, all code that uses these Browser APIs must conform to the MSN specification for the function in question. If the spec is not followed, errors can occur when the RUM JS Agent tries to make use of that API.
The APIs that the RUM JS Agent relies on are listed here along with a links to the relevant specifications.
Resolution
In order to resolve this issue, the other JavaScript code on the page must be modified so that it only returns valid values for this function.
As a temporary solution, you can disable New Real User Monitoring in the application settings.
You can just keep Classic RUM enabled.
Note: Reverting to Classic RUM will result in the loss of new monitoring for RUM data and no data in all third-generation applications, such as Experience Vitals.
Recommandation: Please ensure that you implement browser APIs in your JavaScripts in accordance with specification standards, thus avoiding any potential issues with other tools that utilise these APIs, such as Dynatrace New RUM.
What's next
This issue arises because the New RUM agent introduced functionality that utilises Browser APIs that Classic RUM did not. Therefore, it relies on the correct implementation of these APIs used by other JavaScript on the same page. You can find a list of all the APIs that RUM interacts with on this page.
The process of identifying all the APIs requiring adjustment implementation can be conducted by performing a health check, with the following steps (When new RUM is enabled):
- Open Chrome.
- Open Developer Tools (F12).
- Navigate to the affected web application.
- Open Console and run:
await dynatrace.loadDebugTools();
dynatrace.debugtools.runHealthCheck();
If this article did not help, please open a support ticket, mention that this article was used and provide the following in the ticket:
Link to the RUM Application in your Environment
Link to the JavaScript Error in your Environment
A .HAR file of a page where the problem occurs
Related reading
*Link this article to other relevant configuration or troubleshooting guides, including any applicable troubleshooting maps.
📖 RUM JavaScript Agent gives a 'not iterable error' on Symbol.iterator
