fabio transparently supports Websocket connections by detecting the Upgrade: websocket header in the incoming HTTP(S) request.

Websocket support has been implemented with the websocket library from golang.org/x/net/websocket.

You can test the websocket support with the demo/wsclient and demo/server which implements a simple echo server.

./server -addr -name ws-a -prefix /echo -proto ws
./wsclient -url ws://

You can also run multiple web socket servers on different ports but the same endpoint.

fabio detects on whether to forward the request as HTTP or WS based on the value of the Upgrade header. If the value is websocket it will attempt a websocket connection to the target. Otherwise, it will fall back to HTTP.

One limitation of the current implementation is that the accepted set of protocols has to be symmetric across all services handling it. Only the following combinations will work reliably:

svc-a and svc-b register /foo and accept only HTTP traffic there
svc-a and svc-b register /foo and accept only WS traffic there
svc-a and svc-b register /foo and accept both HTTP and WS traffic there

The following setup (or variations thereof) will not work reliably:

svc-a registers /foo and accept only WS traffic there
svc-b registers /foo and accept only HTTP traffic there

This is not a limitation of the routing itself but because the current configuration does not provide fabio with enough information to make the routing decision since the services do not advertise the protocols they handle on a given endpoint.

This does not look like a big restriction but is also not difficult to extend in a later version assuming there are use cases which require this behavior. For now the services have to be symmetric in the protocols they accept.