Moved memory-cached and disk-cached discovery to their own packages

Kubernetes-commit: 6666049898f93932655fef24f807bc4d6e439fc6

discovery/cached/disk/round_tripper.go

@@ -0,0 +1,62 @@
+/*
+Copyright 2017 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 disk
+
+import (
+	"net/http"
+	"path/filepath"
+
+	"github.com/gregjones/httpcache"
+	"github.com/gregjones/httpcache/diskcache"
+	"github.com/peterbourgon/diskv"
+	"k8s.io/klog"
+)
+
+type cacheRoundTripper struct {
+	rt *httpcache.Transport
+}
+
+// newCacheRoundTripper creates a roundtripper that reads the ETag on
+// response headers and send the If-None-Match header on subsequent
+// corresponding requests.
+func newCacheRoundTripper(cacheDir string, rt http.RoundTripper) http.RoundTripper {
+	d := diskv.New(diskv.Options{
+		BasePath: cacheDir,
+		TempDir:  filepath.Join(cacheDir, ".diskv-temp"),
+	})
+	t := httpcache.NewTransport(diskcache.NewWithDiskv(d))
+	t.Transport = rt
+
+	return &cacheRoundTripper{rt: t}
+}
+
+func (rt *cacheRoundTripper) RoundTrip(req *http.Request) (*http.Response, error) {
+	return rt.rt.RoundTrip(req)
+}
+
+func (rt *cacheRoundTripper) CancelRequest(req *http.Request) {
+	type canceler interface {
+		CancelRequest(*http.Request)
+	}
+	if cr, ok := rt.rt.Transport.(canceler); ok {
+		cr.CancelRequest(req)
+	} else {
+		klog.Errorf("CancelRequest not implemented by %T", rt.rt.Transport)
+	}
+}
+
+func (rt *cacheRoundTripper) WrappedRoundTripper() http.RoundTripper { return rt.rt.Transport }