Based on the official sample provided by Istio, Bookinfo is used to expand, and a service regions from the host is connected. The regions service is used to show which country and region the book review information comes from. In the experiment, you will not only use the DestinationRule, VirtualService and other resources provided by Istio to control the flow of services in the grid, but you will also experience the use of EnvoyFilter to expand Istio's flow control capabilities to achieve more complex flow control scenarios.