add health check

This commit adds a liveness probe to the manager rc and
a healthz endpoint that returns 200 OK.

install.yaml

@@ -147,6 +147,13 @@ spec:
       containers:
       - env: []
         image: gcr.io/dm-k8s-testing/manager:latest
+        imagePullPolicy: Always
+        livenessProbe:
+          httpGet:
+            path: /healthz
+            port: 8080
+          initialDelaySeconds: 30
+          timeoutSeconds: 1
         name: manager
         ports:
         - containerPort: 8080

manager/main.go

@@ -17,6 +17,7 @@ limitations under the License.
 package main
 
 import (
+	"github.com/kubernetes/deployment-manager/util"
 	"github.com/kubernetes/deployment-manager/version"
 
 	"flag"
@@ -38,7 +39,9 @@ type Route struct {
 	Type        string
 }
 
-var routes = []Route{}
+var routes = []Route{
+	{"HealthCheck", "/healthz", "GET", healthCheckHandlerFunc, ""},
+}
 
 // port to listen on
 var port = flag.Int("port", 8080, "The port to listen on")
@@ -80,3 +83,9 @@ func main() {
 	log.Printf("Listening on port %d...", *port)
 	log.Fatal(http.ListenAndServe(address, handler))
 }
+
+func healthCheckHandlerFunc(w http.ResponseWriter, r *http.Request) {
+	handler := "manager: get health"
+	util.LogHandlerEntry(handler, r)
+	util.LogHandlerExitWithText(handler, w, "OK", http.StatusOK)
+}

util/httputil.go

@@ -129,6 +129,15 @@ func LogAndReturnError(handler string, statusCode int, err error, w http.Respons
 	http.Error(w, err.Error(), statusCode)
 }
 
+// LogHandlerExitWithText converts the given string to []byte,
+// writes it to the response body, returns the given status,
+// and then logs the response
+func LogHandlerExitWithText(handler string, w http.ResponseWriter, v string, statusCode int) {
+	msg := []byte(v)
+	WriteResponse(handler, w, msg, "text/plain; charset=UTF-8", statusCode)
+	LogHandlerExit(handler, statusCode, string(msg), w)
+}
+
 // LogHandlerExitWithJSON marshals the given object as JSON,
 // writes it to the response body, returns the given status, and then logs the
 // response.