Configure the RUM cookie domain for web applications
Dynatrace Real User Monitoring uses HTTP cookies to group user actions into sessions and link user actions with their corresponding distributed traces. Browsers include a cookie in the
Cookie request header only if the request URL lies within the scope of the cookie, which is specified by the
Path cookie attributes.
Dynatrace always sets the
Path attribute of the RUM cookies to
/ so that the cookie scope covers all URL paths within a domain. The
Domain attribute is determined automatically by default, but you can also configure it manually for each application.
Automatic cookie domain determination
If you haven't configured the cookie domain, Dynatrace determines it automatically. Dynatrace chooses the effective top-level domain plus one (eTLD+1) of the request URL. For example, Dynatrace chooses the
example.com cookie domain for the
www.example.com domain or the
example.co.uk cookie domain for the
www.example.co.uk domain. With this choice, Dynatrace can capture a continuous session even when your users visit multiple subdomains while interacting with your applications, for example, when they navigate from
Possible issues with automatic cookie domain determination
OneAgent uses the result of host name determination as a starting point when it determines the cookie domain. If there is an uninstrumented component that rewrites the host portion of the URL, it is crucial for automatic cookie domain determination that host name determination is configured correctly. For details, see What can I do if an uninstrumented component rewrites parts of the URL?
Manual cookie domain configuration
In most scenarios, there is no need to configure the cookie domain manually. There are, however, two use cases when this is necessary:
- You need to separate the user actions of different subdomains into separate user sessions.
- Automatic determination of the cookie domain does not work because an uninstrumented component rewrites the host portion of the URL and does not forward the original host information in a request header. The preferable solution is to configure the component to add such a header (see What can I do if an uninstrumented component rewrites parts of the URL? for instructions). However, manual configuration of the cookie domain is also a possible workaround.
Configure cookie domain manually
To configure the cookie domain
- In the Dynatrace menu, go to Web.
- Select the application that you want to configure.
- In the upper-right corner of the application overview page, select More (…) > Edit.
- From the application settings, go to Capturing > Advanced setup.
- Select Cookie and header settings in the upper-right corner of the page.
- Under Domain to be used for cookie placement, enter the required domain.
Possible issues with manual configuration
Configured cookie domain is a public suffix
Browsers do not allow you to set cookies with a
Domain attribute that exceeds a single organization's boundary. Therefore, setting the cookie domain to a public suffix does not work.
Multiple domains without a common eTLD+1 are mapped into the configured application
Since the cookie domain is configured per application, all domains that map to your application should have at least a common eTLD+1 to allow cookie domain definition.
For example, you cannot manually configure the cookie domain for an application where both
www.example.co.uk map. If you choose the cookie domain
example.com, the browser rejects the RUM cookies on requests to
Overlapping cookie domains
If you configure the cookie domain for all or some of your applications manually, you must ensure that the cookie domains of your applications do not overlap.
Consider the following example. The
www.example.com domain is mapped to the Example app, while the
shop.example.com domain is mapped to the Shopping app. By default, the
example.com cookie domain is detected automatically for both domains. If you set the
shop.example.com cookie domain for the Shopping app and your users navigate back and forth between the two applications, ambiguous situations will arise since the RUM cookies for the Example app have the
example.com cookie domain and therefore are also applicable to the Shopping app, which has another set of RUM cookies with the
shop.example.com domain. With this configuration, Dynatrace might randomly split the captured RUM data into short user sessions and user actions, and distributed traces might be not be linked as expected.