This repository represents my experiments while trying to understand in detail how the Envoy control plane worked. As compared to envoy proxy proper there isn't a lot of detailed HOW-TOs on the control plane, but fortunately I found a few good references, specially this one: Envoy hello World

As far code examples, there a few gems that provide great building blocks:

• Envoy's Testing Server Main. This file contains the main() function.
• Envoy's Testing Server Startup Functions. This file contains the start up functions for the various server.
• High Level Envoy API. This file contains high-level APIs to create Envoy resources such as clusters, endpoints and routes.

So, why go through this exercise? Several reasons:

• The code the article above did not work anymore due to changes in the Envoy API code
• I wanted to learn by doing it mostly from scratch
• I wanted to use Golang's core library as much as possible. In other words, the least number of third-party dependencies.

This is still a work in progress. I am still polishing the example.

This was tested with the following:

• MacOS Mojave 10.14.3
• go1.11.5 darwin/amd64
• Envoy v1.9.0

One of the challenges in this exercise was to have the Envoy Proxy run as a container and the application natively. It is not straightforward to have a container access an application running on the host. It took me a while but I finally managed to get the right envoy configuration.

I wanted to have the control plane running natively on the host because I wanted to tinker with it: change, step debug, rerun, stop, Printf, etc.

I had to use two main tricks to have this working:

• use "host.docker.internal" as control plane address
• set the cluster type as type: STRICT_DNS

Assuming you have docker installed and all the other basic stuff, everything you need to run the example should be under testdata.

Run:

./build_all.sh

If everything goes well, you should see the following docker images and a running container

REPOSITORY                         TAG                 IMAGE ID            CREATED              SIZE
envoy_control_plane                v1.9.0              d21d40d3f20a        About a minute ago   189MB
envoyproxy/envoy                   v1.9.0              b02c1418b106        4 months ago         164MB


CONTAINER ID        IMAGE                        COMMAND                  CREATED             STATUS              PORTS                                                NAMES
fb862e600bb0        envoy_control_plane:v1.9.0   "/usr/bin/dumb-init …"   2 minutes ago       Up 2 minutes        0.0.0.0:10000->10000/tcp, 0.0.0.0:19000->19000/tcp   envoy_1_9_0