The Layer of Indirection Pattern
This pattern allows multiple Minor versions of a native service to coexist in the registry without requiring consumers to change the code in their consumer applications, and helps to ensure a graceful migration to the new Minor version.
To implement this pattern, you configure a single virtual service to route each request to the version that is appropriate for each consumer (or group of consumers). That is, you configure the virtual service's Routing step to use either the “content-based routing” option or the “context-based routing” option.
Content-based routing option. Using the content-based routing option, you can route request messages to different endpoints based on specific values that appear in the request message. For example, if a new Minor version contains an additional operation, you can write a rule that routes all requests that reference the newly-added operation to the new Minor version.
Context-based routing option. Using the context-based routing option, you can route request messages to different endpoints based on the identity of the consuming application. For example, if you want to allow only certain consumers to access a new Minor version, you write a rule that routes only their requests to the new Minor version.
