Golang network filter

In this example, we show how the Golang network filter can be used with the Envoy proxy. We also show how the Go plugins can be independently configured at runtime.

The example Go plugin adds a hello, prefix to the requests received from its TCP connections. These modified requests are then proxied to an echo service that is retrieved from the configuration file.

plugin_config:
   "@type": type.googleapis.com/xds.type.v3.TypedStruct
   value:
      echo_server_addr: echo_service

Step 1: Compile the go plugin library

Change to the examples/golang-network directory and build the go plugin library.

$ pwd
envoy/examples/golang-network
$ docker compose -f docker-compose-go.yaml run --rm go_plugin_compile

The compiled library should now be in the lib folder.

$ ls lib
simple.so

Step 2: Start all of our containers

Start all the containers.

$ docker compose pull
$ docker compose up --build -d
$ docker compose ps

 NAME                            COMMAND                  SERVICE             STATUS              PORTS
 golang-network-echo_service-1   "/tcp-echo"              echo_service        running
 golang-network-proxy-1          "/docker-entrypoint.…"   proxy               running             0.0.0.0:10000->10000/tcp

In this example, we start up two containers - an echo service which simply responds to what it has received from its TCP connections, and a proxy service that utilizes a Golang plugin to process and proxy data to the echo service.

Step 3: Send some data to be handled by the Go plugin

The response from the nc command below should include the hello, prefix which will be added by the example Go plugin.

$ echo "world" | nc localhost 10000 2>&1
< hello, world