Application rules uses the URLs of incoming http(s) requests to group them to applications. By default all incoming traffic is assigned to the default application called "my web application". Now you can start to group this traffic by adding application rules based on URLs.
As the domain (host) part of the URL is typically set in the host header of an request. But depending on the used infrastructure the host header may not have the original host name and the original host name is in an other header like the x-forwarded-for.
So if a request comes in, Dynatrace checks for some headers for getting the correct domain (host) to build the complete URL. You can see the default headers and the order for this domain detection at the end of the application rule settings view. If needed you can add your own header which is then used for the domain part of the URL.
After the domain lookup, the complete URL will be used for application detection.
Back to your questions:
- Application rules are based on URLs (the domain or host name) is part of the URL. The domain matches rules are just shortcuts to make the configuration easier. As the domain (host name) is only available within a header, Dynatrace looks for existence of some typical "host" headers in a given sequence, takes the first one found and uses this for the domain part of the URL.
- This old post is not relevant anymore. Applications are not created automatically. You have to define an application rule.
- You can use http headers for application creation. Only the host header as part of the full URL is part of the application detection. Of course you can add every header to be considered as host header, but then you will see this header value also as host or domain in all views.
Does this help?
