Merge pull request #303 from justinsb/direct_transport

mockkubeapiserver: Support direct mode without listening on a socket

mockkubeapiserver/direct_http.go

@@ -0,0 +1,168 @@
+/*
+Copyright 2022 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package mockkubeapiserver
+
+import (
+	"bytes"
+	"io"
+	"net/http"
+	"sync"
+)
+
+// DirectTransport returns an http.RoundTripper that can serve requests without needing
+// a listening socket.
+func (s *MockKubeAPIServer) DirectTransport() http.RoundTripper {
+	return &directHTTPRoundTripper{server: s}
+}
+
+type directHTTPRoundTripper struct {
+	server *MockKubeAPIServer
+}
+
+var _ http.RoundTripper = &directHTTPRoundTripper{}
+
+// RoundTrip implements http.RoundTripper
+func (t *directHTTPRoundTripper) RoundTrip(r *http.Request) (*http.Response, error) {
+	w := newDirectResponseWriter()
+
+	go func() {
+		t.server.ServeHTTP(w, r)
+		w.close()
+	}()
+
+	// response blocks until we have the headers, at least.
+	return w.response()
+}
+
+// directResponseWriter implements http.ResponseWriter.
+type directResponseWriter struct {
+	statusCode int
+	header     http.Header
+
+	// mutex guards all the below values
+	mutex sync.Mutex
+	// cond is signalled when one of the below values changes
+	cond *sync.Cond
+	// wroteHeader is true if we know the status code & headers
+	wroteHeader bool
+	// done is true if we have finished writing the response (the handler has returned)
+	done bool
+	// body is a buffer / pipe of our response body.
+	// We can't use io.Pipe because it is blocking.
+	body bytes.Buffer
+}
+
+func newDirectResponseWriter() *directResponseWriter {
+	w := &directResponseWriter{}
+	w.cond = sync.NewCond(&w.mutex)
+	w.header = make(http.Header)
+	return w
+}
+
+var _ http.ResponseWriter = &directResponseWriter{}
+
+// response constructs an http.Response, blocking until we have at least the headers.
+func (w *directResponseWriter) response() (*http.Response, error) {
+	w.mutex.Lock()
+	for !w.wroteHeader {
+		w.cond.Wait()
+	}
+
+	response := &http.Response{}
+	response.Body = &responseReader{w: w}
+	response.Header = w.header
+	response.StatusCode = w.statusCode
+	if response.StatusCode == 0 {
+		response.StatusCode = 200
+	}
+
+	w.mutex.Unlock()
+
+	return response, nil
+}
+
+type responseReader struct {
+	w *directResponseWriter
+}
+
+var _ io.ReadCloser = &responseReader{}
+
+// Close implements io.ReadCloser
+func (r *responseReader) Close() error {
+	// TODO: we could try to signal to the http server that the connection is closed
+	return nil
+}
+
+// Read implements io.ReadCloser
+func (r *responseReader) Read(data []byte) (int, error) {
+	w := r.w
+
+	w.mutex.Lock()
+	for {
+		n, err := w.body.Read(data)
+		if n == 0 {
+			if err == io.EOF {
+				if w.done {
+					w.mutex.Unlock()
+					return 0, io.EOF
+				}
+				w.cond.Wait()
+				continue
+			}
+		}
+
+		w.mutex.Unlock()
+		return n, err
+	}
+}
+
+func (w *directResponseWriter) close() {
+	w.mutex.Lock()
+	if !w.wroteHeader {
+		w.wroteHeader = true
+	}
+	w.done = true
+	w.cond.Broadcast()
+	w.mutex.Unlock()
+}
+
+// Header implements http.ResponseWriter
+func (w *directResponseWriter) Header() http.Header {
+	return w.header
+}
+
+// Write implements http.ResponseWriter
+func (w *directResponseWriter) Write(b []byte) (int, error) {
+	w.mutex.Lock()
+	if !w.wroteHeader {
+		w.wroteHeader = true
+	}
+	n, err := w.body.Write(b)
+	w.cond.Broadcast()
+	w.mutex.Unlock()
+
+	return n, err
+}
+
+// WriteHeader implements http.ResponseWriter
+func (w *directResponseWriter) WriteHeader(statusCode int) {
+	w.mutex.Lock()
+	w.statusCode = statusCode
+	w.wroteHeader = true
+	w.cond.Broadcast()
+	w.mutex.Unlock()
+}