Kubernetes events watcher

Kubewatcher watches the Kubernetes API for Watches that have been
configured on the fission controller.  It then posts that event to the
function configured in the watch.

kubewatcher/webhookposter.go

@@ -0,0 +1,79 @@
+/*
+Copyright 2016 The Fission 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 kubewatcher
+
+import (
+	"io"
+	"log"
+	"net/http"
+	"strings"
+)
+
+type (
+	Poster struct {
+		routerUrl      string
+		requestChannel chan *postRequest
+	}
+	postRequest struct {
+		eventType   string
+		relativeUrl string
+		body        io.Reader
+	}
+)
+
+func MakePoster(routerUrl string) *Poster {
+	p := &Poster{
+		routerUrl:      strings.TrimSuffix(routerUrl, "/"),
+		requestChannel: make(chan *postRequest, 32), // buffered channel
+	}
+	go p.svc()
+	return p
+}
+
+func (p *Poster) svc() {
+	for {
+		r := <-p.requestChannel
+
+		url := p.routerUrl + r.relativeUrl
+		req, err := http.NewRequest("POST", url, r.body)
+		if err != nil {
+			log.Printf("Failed to create request to %v", r.relativeUrl)
+		}
+		req.Header.Add("X-Kubernetes-Event-Type", r.eventType)
+		req.Header.Add("X-Fission-Request-Async", "true")
+
+		resp, err := http.DefaultClient.Do(req)
+		if err != nil {
+			log.Printf("request failed: %v", r)
+			// TODO retries, persistence, etc.
+		}
+
+		resp.Body.Close()
+		if resp.StatusCode != 200 {
+			log.Printf("request failed: %v", resp.StatusCode)
+			// TODO retries etc.
+		}
+	}
+}
+
+func (p *Poster) Post(eventType, relativeUrl string, body io.Reader) {
+	p.requestChannel <- &postRequest{
+		eventType:   eventType,
+		relativeUrl: relativeUrl,
+		body:        body,
+	}
+}