Web sockets error

[aalubin]

I am trying to use keyckloack-proxy as a front-end for on-premise kubernetes cluster.
Everything works, but one of the UI features, that opens a shell on the pod using web sockets.
When I try to open a shell, the connection closes after a second with the following proxy error :

1.5119475422049198e+09	debug	keycloak-proxy/forwarding.go:43	upgrading the connnection	{"client_ip": "127.0.0.1:57189"}
Panic: interface conversion: *middleware.flushWriter is not http.Hijacker: missing method Hijack
goroutine 237 [running]:
runtime/debug.Stack(0x61, 0x0, 0x0)
	/usr/local/Cellar/go/1.9.2/libexec/src/runtime/debug/stack.go:24 +0xa7
runtime/debug.PrintStack()
	/usr/local/Cellar/go/1.9.2/libexec/src/runtime/debug/stack.go:16 +0x22
github.com/pressly/chi/middleware.Recoverer.func1.1(0xc420609f00, 0x18b5080, 0xc4201f89a0)
	/Users/alon.l/go/src/github.com/pressly/chi/middleware/recoverer.go:28 +0x1c0
panic(0x1547a00, 0xc420157380)
	/usr/local/Cellar/go/1.9.2/libexec/src/runtime/panic.go:491 +0x283
main.tryUpdateConnection(0xc4206ce000, 0x1a86360, 0xc420157300, 0xc420150380, 0x0, 0x0)
	/Users/alon.l/go/src/github.com/gambol99/keycloak-proxy/utils.go:257 +0xc8
main.(*oauthProxy).proxyMiddleware.func1(0x1a86360, 0xc420157300, 0xc4206ce000)
	/Users/alon.l/go/src/github.com/gambol99/keycloak-proxy/forwarding.go:44 +0x524
net/http.HandlerFunc.ServeHTTP(0xc4204dc380, 0x1a86360, 0xc420157300, 0xc4206ce000)
	/usr/local/Cellar/go/1.9.2/libexec/src/net/http/server.go:1918 +0x44
main.(*oauthProxy).securityMiddleware.func1(0x1a86360, 0xc420157300, 0xc4206ce000)
	/Users/alon.l/go/src/github.com/gambol99/keycloak-proxy/middleware.go:378 +0x306
net/http.HandlerFunc.ServeHTTP(0xc42023e000, 0x1a86360, 0xc420157300, 0xc4206ce000)
	/usr/local/Cellar/go/1.9.2/libexec/src/net/http/server.go:1918 +0x44
main.entrypointMiddleware.func1(0x18b5080, 0xc4201f89a0, 0xc420609f00)
	/Users/alon.l/go/src/github.com/gambol99/keycloak-proxy/middleware.go:55 +0x23b
net/http.HandlerFunc.ServeHTTP(0xc4204dc420, 0x18b5080, 0xc4201f89a0, 0xc420609f00)
	/usr/local/Cellar/go/1.9.2/libexec/src/net/http/server.go:1918 +0x44
github.com/pressly/chi/middleware.Recoverer.func1(0x18b5080, 0xc4201f89a0, 0xc420609f00)
	/Users/alon.l/go/src/github.com/pressly/chi/middleware/recoverer.go:35 +0x9f
net/http.HandlerFunc.ServeHTTP(0xc4204dc440, 0x18b5080, 0xc4201f89a0, 0xc420609f00)
	/usr/local/Cellar/go/1.9.2/libexec/src/net/http/server.go:1918 +0x44
github.com/pressly/chi.(*Mux).ServeHTTP(0xc42005c720, 0x18b5080, 0xc4201f89a0, 0xc420609e00)
	/Users/alon.l/go/src/github.com/pressly/chi/mux.go:81 +0x221
net/http.serverHandler.ServeHTTP(0xc420158c30, 0x18b5080, 0xc4201f89a0, 0xc420609e00)
	/usr/local/Cellar/go/1.9.2/libexec/src/net/http/server.go:2619 +0xb4
net/http.(*conn).serve(0xc4206b8140, 0x18b5d40, 0xc4201571c0)
	/usr/local/Cellar/go/1.9.2/libexec/src/net/http/server.go:1801 +0x71d
created by net/http.(*Server).Serve
	/usr/local/Cellar/go/1.9.2/libexec/src/net/http/server.go:2720 +0x288

The proxy version I use:
keycloak-proxy version v2.1.0-rc5 (git+sha: no gitsha provided, built: 01-01-1970)

Is it a bug?
am I missing a flag, again? :)

[ginkel]

Having also just hit this issue, I tried figuring out what is causing this to break. AFAICS, the issue is caused by a chi middleware.flushWriter being used instead of a middleware.httpFancyWriter. The decision which one to use seems to happen in NewWrapResponseWriter and the exact logic depends on whether HTTP/2 is in use.

func NewWrapResponseWriter(w http.ResponseWriter, protoMajor int) WrapResponseWriter {
	_, cn := w.(http.CloseNotifier)
	_, fl := w.(http.Flusher)

	bw := basicWriter{ResponseWriter: w}

	if protoMajor == 2 {
		_, ps := w.(http.Pusher)
		if cn && fl && ps {
			return &http2FancyWriter{bw}
		}
	} else {
		_, hj := w.(http.Hijacker)
		_, rf := w.(io.ReaderFrom)
		if cn && fl && hj && rf {
			return &httpFancyWriter{bw}
		}
	}
	if fl {
		return &flushWriter{bw}
	}

	return &bw
}

This is most likely the culprit in my setup as keycloak-proxy is running behind an nginx reverse proxy, so connections get downgraded to HTTP/1.1 and at least one of cn, hj or rf is false causing the code to fall through to the flushWriter creation.

[gambol99]

should be fixed in #303

[ginkel]

Works like a charm, thanks @gambol99! :-)