Setup

edit /etc/hosts

127.0.0.1 be.cluster.local xds.domain.com

gRPC Server

Start gRPC Servers

cd app/
go run src/server/grpc_server.go --grpcport :50051 --servername server1

NOTE If you change the ports or run more servers, ensure you update the list when you start the xDS server

xDS Server

Now start the xDS server:

cd xds-new
go run main.go 

NOTE Update the list of --upstream_port flags to reflect the list of ports for the gRPC servers that you started

gRPC Client (xDS)

• xds_bootstrap.json:

{
  "xds_servers": [
    {
      "server_uri": "xds.domain.com:18000",
      "channel_creds": [
        {
          "type": "insecure"
        }
      ],
      "server_features": ["xds_v3"]     
    }
  ],
  "node": {
    "id": "b7f9c818-fb46-43ca-8662-d3bdbcf7ec18~10.0.0.1",
    "metadata": {
      "R_GCP_PROJECT_NUMBER": "123456789012"
    },
    "locality": {
      "zone": "us-central1-a"
    }
  }
}

Then:

go run src/client/grpc_client.go

in the debug logs that it connected to port :50051

INFO: 2020/04/21 16:14:42 Subchannel picks a new address "be.cluster.local:50051" to connect

The grpc client will issue grpc requests every 5 seconds using the list of backend services it gets from the xds server. Since the xds server will abruptly rotate the grpc backend servers, the client will suddenly connect to server2

INFO: 2020/04/21 16:16:08 Subchannel picks a new address "be.cluster.local:50052" to connect

The port it connected to is :50052

Right, that's it!

---

$ go run src/grpc_client.go 

2021/06/15 10:47:26 RPC Response: 0 message:"Hello unary RPC msg   from server1" 
2021/06/15 10:47:31 RPC Response: 1 message:"Hello unary RPC msg   from server1" 
2021/06/15 10:47:36 RPC Response: 2 message:"Hello unary RPC msg   from server1" 
2021/06/15 10:47:41 RPC Response: 3 message:"Hello unary RPC msg   from server1" 
2021/06/15 10:47:46 RPC Response: 4 message:"Hello unary RPC msg   from server1" 
2021/06/15 10:47:51 RPC Response: 5 message:"Hello unary RPC msg   from server1" 
2021/06/15 10:47:56 RPC Response: 6 message:"Hello unary RPC msg   from server1" 
2021/06/15 10:48:01 RPC Response: 7 message:"Hello unary RPC msg   from server1" 
2021/06/15 10:48:06 RPC Response: 8 message:"Hello unary RPC msg   from server1" 
2021/06/15 10:48:11 RPC Response: 9 message:"Hello unary RPC msg   from server1" 
2021/06/15 10:48:16 RPC Response: 10 message:"Hello unary RPC msg   from server1" 
2021/06/15 10:48:21 RPC Response: 11 message:"Hello unary RPC msg   from server1" 
2021/06/15 10:48:26 RPC Response: 12 message:"Hello unary RPC msg   from server2"  
2021/06/15 10:48:31 RPC Response: 13 message:"Hello unary RPC msg   from server2" 
2021/06/15 10:48:36 RPC Response: 14 message:"Hello unary RPC msg   from server2" 

---

If you want more details...

References

• Envoy Listener proto
• Envoy Cluster proto
• Envoy Endpoint proto