Support HEAD request for http check

api/agent.go

@@ -76,6 +76,7 @@ type AgentServiceCheck struct {
 	Status            string `json:",omitempty"`
 	Notes             string `json:",omitempty"`
 	TLSSkipVerify     bool   `json:",omitempty"`
+	Head              bool   `json:",omitempty"`
 
 	// In Consul 0.7 and later, checks that are associated with a service
 	// may also contain this optional DeregisterCriticalServiceAfter field,

command/agent/agent.go

@@ -1158,6 +1158,7 @@ func (a *Agent) AddCheck(check *structs.HealthCheck, chkType *CheckType, persist
 				Timeout:       chkType.Timeout,
 				Logger:        a.logger,
 				TLSSkipVerify: chkType.TLSSkipVerify,
+				Head:          chkType.Head,
 			}
 			http.Start()
 			a.checkHTTPs[check.CheckID] = http

command/agent/check.go

@@ -49,6 +49,7 @@ type CheckType struct {
 	DockerContainerID string
 	Shell             string
 	TLSSkipVerify     bool
+	Head              bool
 
 	Timeout time.Duration
 	TTL     time.Duration
@@ -342,6 +343,7 @@ type CheckHTTP struct {
 	Timeout       time.Duration
 	Logger        *log.Logger
 	TLSSkipVerify bool
+	Head          bool
 
 	httpClient *http.Client
 	stop       bool
@@ -420,7 +422,11 @@ func (c *CheckHTTP) run() {
 
 // check is invoked periodically to perform the HTTP check
 func (c *CheckHTTP) check() {
-	req, err := http.NewRequest("GET", c.HTTP, nil)
+	method := http.MethodGet
+	if c.Head {
+		method = http.MethodHead
+	}
+	req, err := http.NewRequest(method, c.HTTP, nil)
 	if err != nil {
 		c.Logger.Printf("[WARN] agent: http request failed '%s': %s", c.HTTP, err)
 		c.Notify.UpdateCheck(c.CheckID, structs.HealthCritical, err.Error())

command/agent/check_test.go

@@ -10,6 +10,7 @@ import (
 	"net/http/httptest"
 	"os"
 	"os/exec"
+	"regexp"
 	"strings"
 	"testing"
 	"time"
@@ -213,10 +214,12 @@ func TestCheckTTL(t *testing.T) {
 func mockHTTPServer(responseCode int) *httptest.Server {
 	mux := http.NewServeMux()
 	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
-		// Body larger than 4k limit
-		body := bytes.Repeat([]byte{'a'}, 2*CheckBufSize)
 		w.WriteHeader(responseCode)
-		w.Write(body)
+		if r.Method != http.MethodHead {
+			// Body larger than 4k limit
+			body := bytes.Repeat([]byte{'a'}, 2*CheckBufSize)
+			w.Write(body)
+		}
 		return
 	})
 
@@ -535,6 +538,41 @@ func mockTCPServer(network string) net.Listener {
 
 	return listener
 }
+func TestCheckHTTP_Head_true_empty_output(t *testing.T) {
+	server := mockHTTPServer(200)
+	defer server.Close()
+
+	mock := &MockNotify{
+		state:   make(map[types.CheckID]string),
+		updates: make(map[types.CheckID]int),
+		output:  make(map[types.CheckID]string),
+	}
+
+	check := &CheckHTTP{
+		Notify:   mock,
+		CheckID:  types.CheckID("head_true"),
+		HTTP:     server.URL,
+		Interval: 5 * time.Millisecond,
+		Logger:   log.New(os.Stderr, "", log.LstdFlags),
+		Head:     true,
+	}
+
+	check.Start()
+	defer check.Stop()
+
+	testutil.WaitForResult(func() (bool, error) {
+		if mock.state["head_true"] != structs.HealthPassing {
+			return false, fmt.Errorf("should be passing '%v'", mock.state)
+		}
+		match, _ := regexp.MatchString("^.* Output: $", mock.output["head_true"])
+		if !match {
+			return false, fmt.Errorf("check output should be empty '%v'", mock.output["head_true"])
+		}
+		return true, nil
+	}, func(err error) {
+		t.Fatalf("err: %s", err)
+	})
+}
 
 func expectTCPStatus(t *testing.T, tcp string, status string) {
 	mock := &MockNotify{

command/agent/config.go

@@ -9,6 +9,7 @@ import (
 	"os"
 	"path/filepath"
 	"sort"
+	"strconv"
 	"strings"
 	"time"
 
@@ -1099,7 +1100,7 @@ AFTER_FIX:
 }
 
 func FixupCheckType(raw interface{}) error {
-	var ttlKey, intervalKey, timeoutKey string
+	var ttlKey, intervalKey, timeoutKey, headKey string
 	const deregisterKey = "DeregisterCriticalServiceAfter"
 
 	// Handle decoding of time durations
@@ -1116,6 +1117,8 @@ func FixupCheckType(raw interface{}) error {
 			intervalKey = k
 		case "timeout":
 			timeoutKey = k
+		case "head":
+			headKey = k
 		case "deregister_critical_service_after":
 			rawMap[deregisterKey] = v
 			delete(rawMap, k)
@@ -1131,6 +1134,17 @@ func FixupCheckType(raw interface{}) error {
 		}
 	}
 
+	if head, ok := rawMap[headKey]; ok {
+		headS, ok := head.(string)
+		if ok {
+			if bol, err := strconv.ParseBool(headS); err != nil {
+				return err
+			} else {
+				rawMap[headKey] = bol
+			}
+		}
+	}
+
 	if ttl, ok := rawMap[ttlKey]; ok {
 		ttlS, ok := ttl.(string)
 		if ok {

command/agent/config_test.go

@@ -1248,6 +1248,15 @@ func TestDecodeConfig_Checks(t *testing.T) {
 				"timeout": "100ms",
 				"service_id": "insecure-sslservice",
 				"tls_skip_verify": true
+			},
+			{
+				"id": "chk7",
+				"name": "service:elasticsearch:health",
+				"HTTP": "http://localhost:9200/_cluster_health",
+				"interval": "10s",
+				"timeout": "100ms",
+				"service_id": "elasticsearch",
+                "head": true
 			}
 		]
 	}`
@@ -1316,6 +1325,17 @@ func TestDecodeConfig_Checks(t *testing.T) {
 					TLSSkipVerify: true,
 				},
 			},
+			&CheckDefinition{
+				ID:        "chk7",
+				Name:      "service:elasticsearch:health",
+				ServiceID: "elasticsearch",
+				CheckType: CheckType{
+					HTTP:     "http://localhost:9200/_cluster_health",
+					Interval: 10 * time.Second,
+					Timeout:  100 * time.Millisecond,
+					Head:     true,
+				},
+			},
 		},
 	}
 

website/source/docs/agent/checks.html.markdown

@@ -37,7 +37,8 @@ There are five different kinds of checks:
   limited to roughly 4K. Responses larger than this will be truncated. HTTP checks
   also support SSL. By default, a valid SSL certificate is expected. Certificate
   verification can be turned off by setting the `tls_skip_verify` field to `true`
-  in the check definition.
+  in the check definition. The request will be , by default, a `GET` but can be
+  turned into a `HEAD` by setting `head` field to `true`.
 
 * TCP + Interval - These checks make an TCP connection attempt every Interval
   (e.g. every 30 seconds) to the specified IP/hostname and port. If no hostname

website/source/docs/agent/http/agent.html.markdown

@@ -291,7 +291,8 @@ body must look like:
   "TCP": "example.com:22",
   "Interval": "10s",
   "TTL": "15s",
-  "TLSSkipVerify": true
+  "TLSSkipVerify": true,
+  "Head": true,
 }
 ```