Envoy websocket filter example.

NOTE: Require latest version of envoy which applied the merge request #2070

Build

go get github.com/tangxinfa/envoy-socket.io-example
cd $GOPATH/src/github.com/tangxinfa/envoy-socket.io-example
glide install
go build

Run

Single service node

./envoy-socket.io-example -addr 127.0.0.1:8001 -logtostderr &
envoy --base-id 1 --config-path ./envoy.json

Open http://localhost:9001/index.html in your favorite browser, if socket.io connected to server a welcome message will arrive, you can input something then click send, the server will echo the same contents back.

Multiple service nodes

./envoy-socket.io-example -addr 127.0.0.1:8002  -logtostderr &
./envoy-socket.io-example -addr 127.0.0.1:8003  -logtostderr &
./envoy-socket.io-example -addr 127.0.0.1:8004  -logtostderr &
envoy --base-id 2 --config-path ./envoy2.json

Open http://localhost:9002/index2.html in your favorite browser, open it in multiple tabs. In any tab, if socket.io connected to server a welcome message will arrive, you can input something then click send, the server will echo the same contents back.

The key ideas for use envoy to proxy socket.io on multiple service nodes:

1. socket.io client must set transports option to ['websocket', 'polling'].
2. socket.io client must put the user identifier on url.
3. envoy upstream cluster use ring_hash load balance type.
4. envoy websocket route add hash_policy with header_name referrer. See envoy2.json and index2.html for details.

If you try to open http://localhost:9002/index.html, you will see many websocket reconnect events, because socket.io's transports option default is ['polling', 'websocket'], it need two http round-trip to establish a websocket connection, in current envoy's implementation, the first http polling request can schedule to the same upstream host, but the second is websocket upgrade request, which use TcpProxy to connect upstream, it only support random hash policy, which fails the socket.io handshake process.