multipurpose xds

This started as the example xds server from envoyproxy/go-control-plane, and several features have been added.

It is intended to be used as a control plane for Grpc services to demonstrate fault tolerance features like Fault Injection and traffic direction.

Added features:

• load a yaml Bootstrap config for serving Listener and Cluster resources
• support grpc service introspection

TODO:

• document required resources from the config, and their simplest form.
• custom grpc service config that creates the right resources
• server-side xds integrations, allowing for fault injection on server side

Example xDS Server

This is an example of a trivial xDS V3 control plane server. It serves an Envoy configuration that's roughly equivalent to the one used by the Envoy "Quick Start" docs: a simple http proxy. You can run the example using the project top-level Makefile, e.g.:

$ make example

The Makefile builds the example server and then runs build/example.sh which runs both Envoy and the example server. The example server serves a configuration defined in internal/example/resource.go. If everything works correctly, you should be able to open a browser to http://localhost:10000 and see Envoy's website.

Files

• main/main.go is the example program entrypoint. It instantiates the cache and xDS server and runs the xDS server process.
• resource.go generates a Snapshot structure which describes the configuration that the xDS server serves to Envoy.
• server.go runs the xDS control plane server.
• logger.go implements the pkg/log/Logger interface which provides logging services to the cache.