Add httpHeaders to httpGet liveness probe

Also update existing documentation and try to steer users away from 'host'.
Add validation.

pkg/probe/http/http.go

@@ -36,7 +36,7 @@ func New() HTTPProber {
 }
 
 type HTTPProber interface {
-	Probe(url *url.URL, timeout time.Duration) (probe.Result, string, error)
+	Probe(url *url.URL, headers http.Header, timeout time.Duration) (probe.Result, string, error)
 }
 
 type httpProber struct {
@@ -44,20 +44,26 @@ type httpProber struct {
 }
 
 // Probe returns a ProbeRunner capable of running an http check.
-func (pr httpProber) Probe(url *url.URL, timeout time.Duration) (probe.Result, string, error) {
-	return DoHTTPProbe(url, &http.Client{Timeout: timeout, Transport: pr.transport})
+func (pr httpProber) Probe(url *url.URL, headers http.Header, timeout time.Duration) (probe.Result, string, error) {
+	return DoHTTPProbe(url, headers, &http.Client{Timeout: timeout, Transport: pr.transport})
 }
 
 type HTTPGetInterface interface {
-	Get(u string) (*http.Response, error)
+	Do(req *http.Request) (*http.Response, error)
 }
 
 // DoHTTPProbe checks if a GET request to the url succeeds.
 // If the HTTP response code is successful (i.e. 400 > code >= 200), it returns Success.
 // If the HTTP response code is unsuccessful or HTTP communication fails, it returns Failure.
 // This is exported because some other packages may want to do direct HTTP probes.
-func DoHTTPProbe(url *url.URL, client HTTPGetInterface) (probe.Result, string, error) {
-	res, err := client.Get(url.String())
+func DoHTTPProbe(url *url.URL, headers http.Header, client HTTPGetInterface) (probe.Result, string, error) {
+	req, err := http.NewRequest("GET", url.String(), nil)
+	if err != nil {
+		// Convert errors into failures to catch timeouts.
+		return probe.Failure, err.Error(), nil
+	}
+	req.Header = headers
+	res, err := client.Do(req)
 	if err != nil {
 		// Convert errors into failures to catch timeouts.
 		return probe.Failure, err.Error(), nil

pkg/probe/http/http_test.go

@@ -42,8 +42,8 @@ func containsAny(s string, substrs []string) bool {
 }
 
 func TestHTTPProbeChecker(t *testing.T) {
-	handleReq := func(s int, body string) func(w http.ResponseWriter) {
-		return func(w http.ResponseWriter) {
+	handleReq := func(s int, body string) func(w http.ResponseWriter, r *http.Request) {
+		return func(w http.ResponseWriter, r *http.Request) {
 			w.WriteHeader(s)
 			w.Write([]byte(body))
 		}
@@ -51,8 +51,9 @@ func TestHTTPProbeChecker(t *testing.T) {
 
 	prober := New()
 	testCases := []struct {
-		handler func(w http.ResponseWriter)
-		health  probe.Result
+		handler    func(w http.ResponseWriter, r *http.Request)
+		reqHeaders http.Header
+		health     probe.Result
 		// go1.5: error message changed for timeout, need to support
 		// both old and new
 		accBodies []string
@@ -60,18 +61,41 @@ func TestHTTPProbeChecker(t *testing.T) {
 		// The probe will be filled in below.  This is primarily testing that an HTTP GET happens.
 		{
 			handleReq(http.StatusOK, "ok body"),
+			nil,
 			probe.Success,
 			[]string{"ok body"},
 		},
+		{
+			// Echo handler that returns the contents of request headers in the body
+			func(w http.ResponseWriter, r *http.Request) {
+				w.WriteHeader(200)
+				output := ""
+				for k, arr := range r.Header {
+					for _, v := range arr {
+						output += fmt.Sprintf("%s: %s\n", k, v)
+					}
+				}
+				w.Write([]byte(output))
+			},
+			http.Header{
+				"X-Muffins-Or-Cupcakes": {"muffins"},
+			},
+			probe.Success,
+			[]string{
+				"X-Muffins-Or-Cupcakes: muffins",
+			},
+		},
 		{
 			handleReq(FailureCode, "fail body"),
+			nil,
 			probe.Failure,
 			[]string{fmt.Sprintf("HTTP probe failed with statuscode: %d", FailureCode)},
 		},
 		{
-			func(w http.ResponseWriter) {
+			func(w http.ResponseWriter, r *http.Request) {
 				time.Sleep(3 * time.Second)
 			},
+			nil,
 			probe.Failure,
 			[]string{
 				"use of closed network connection",
@@ -82,7 +106,7 @@ func TestHTTPProbeChecker(t *testing.T) {
 	for _, test := range testCases {
 		// TODO: Close() this when fix #19254
 		server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-			test.handler(w)
+			test.handler(w, r)
 		}))
 		u, err := url.Parse(server.URL)
 		if err != nil {
@@ -96,7 +120,7 @@ func TestHTTPProbeChecker(t *testing.T) {
 		if err != nil {
 			t.Errorf("Unexpected error: %v", err)
 		}
-		health, output, err := prober.Probe(u, 1*time.Second)
+		health, output, err := prober.Probe(u, test.reqHeaders, 1*time.Second)
 		if test.health == probe.Unknown && err == nil {
 			t.Errorf("Expected error")
 		}