Implement a very simple request cache

This really only makes sense for the proxy mode, otherwise it would
"cache" the already loaded responses, but the responses *are* the cache.

Maybe the cache should be a separate variable and we should forbid to
use `-cache` without `-proxy-url`?

go/fake-http/fake-http.go

@@ -28,6 +28,7 @@ var flags struct {
	proxyClientKey  string
	proxyMinikube bool
	cache         bool
}
func init() {
@@ -37,6 +38,7 @@ func init() {
	flag.StringVar(&flags.proxyClientKey, "proxy-client-key", "", "Client key to use when connecting to proxy")
	flag.BoolVar(&flags.proxyMinikube, "proxy-minikube", false, "Shortcut for -proxy-url https://$(minikube ip):8443 -proxy-client-cert ~/.minikube/client.crt -proxy-client-key ~/.minikube/client.key")
	flag.BoolVar(&flags.cache, "cache", false, "Cache all requests")
}
func main() {
@@ -69,14 +71,19 @@ func main() {
	http.HandleFunc("/", func(w http.ResponseWriter, req *http.Request) {
		responses.Load(responsesPath)
		stub := responses.Match(req)
		haveCachedStub := flags.cache && stub != nil
		var resp *http.Response
		if flags.proxyURL != "" {
		if flags.proxyURL != "" && !haveCachedStub {
			resp = respondWithProxy(flags.proxyURL, &cert, w, req)
		} else {
			resp = respondWithStub(responses, w, req)
			resp = respondWithStub(stub, w, req)
		}
		requestLog.Log(req, resp)
		e := requestLog.Log(req, resp)
		if flags.cache {
			responses.Add(e.AsResponse())
		}
	})
	http.HandleFunc("/_log", func(w http.ResponseWriter, req *http.Request) {
@@ -140,12 +147,7 @@ func proxyMinikube() error {
	return nil
}
func respondWithStub(responses Responses, w http.ResponseWriter, req *http.Request) *http.Response {
	resp := responses.Match(req)
	if resp == nil {
		resp = &Response{Status: 404, Body: "Not found"}
	}
func respondWithStub(resp *Response, w http.ResponseWriter, req *http.Request) *http.Response {
	time.Sleep(resp.Delay)
	if resp.RandomDelay > 0 {
		time.Sleep(time.Duration(rand.Intn(int(resp.RandomDelay))))
@@ -227,7 +229,7 @@ func renderYAML(w http.ResponseWriter, responses []Response) error {
type Log []LogEntry
// Log logs the request/response pair.
func (l *Log) Log(req *http.Request, resp *http.Response) {
func (l *Log) Log(req *http.Request, resp *http.Response) *LogEntry {
	userAgent := req.Header.Get("User-Agent")
	log.Printf("%s %s - %d (%s, %q)", req.Method, req.URL, resp.StatusCode, req.RemoteAddr, userAgent)
@@ -249,6 +251,7 @@ func (l *Log) Log(req *http.Request, resp *http.Response) {
	}
	io.Copy(e.responseBody, resp.Body)
	*l = append(*l, e)
	return &e
}
// AsResponses returns the log as a list of response definition.
@@ -351,6 +354,12 @@ func (rs *Responses) Match(req *http.Request) *Response {
	return nil
}
// Add adds the response to the log, to include it in future Match
// calls.
func (rs *Responses) Add(r Response) {
	*rs = append(*rs, r)
}
// Load loads responses from the YAML file at path.
func (rs *Responses) Load(path string) {
	if path == "" {