Add healthcheck command

cmd/traefik/traefik.go

@@ -1,9 +1,11 @@
 package main
 
 import (
+	"crypto/tls"
 	"encoding/json"
 	"fmt"
 	fmtlog "log"
+	"net/http"
 	"os"
 	"path/filepath"
 	"reflect"
@@ -97,6 +99,43 @@ Complete documentation is available at https://traefik.io`,
 		},
 	}
 
+	healthcheckCmd := &flaeg.Command{
+		Name:                  "healthcheck",
+		Description:           `Calls traefik /ping to check health (web provider must be enabled)`,
+		Config:                traefikConfiguration,
+		DefaultPointersConfig: traefikPointersConfiguration,
+		Run: func() error {
+			if traefikConfiguration.Web == nil {
+				fmt.Println("Please enable the web provider to use healtcheck.")
+				os.Exit(1)
+			}
+			client := &http.Client{Timeout: 5 * time.Second}
+			protocol := "http"
+			if len(traefikConfiguration.Web.CertFile) > 0 {
+				protocol = "https"
+				tr := &http.Transport{
+					TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
+				}
+				client.Transport = tr
+			}
+			resp, err := client.Head(protocol + "://" + traefikConfiguration.Web.Address + "/ping")
+			if err != nil {
+				fmt.Printf("Error calling healthcheck: %s\n", err)
+				os.Exit(1)
+			}
+			if resp.StatusCode != http.StatusOK {
+				fmt.Printf("Bad healthcheck status: %s\n", resp.Status)
+				os.Exit(1)
+			}
+			fmt.Printf("OK: %s\n", resp.Request.URL)
+			os.Exit(0)
+			return nil
+		},
+		Metadata: map[string]string{
+			"parseAllSources": "true",
+		},
+	}
+
 	//init flaeg source
 	f := flaeg.New(traefikCmd, os.Args[1:])
 	//add custom parsers
@@ -112,6 +151,7 @@ Complete documentation is available at https://traefik.io`,
 	f.AddCommand(newVersionCmd())
 	f.AddCommand(newBugCmd(traefikConfiguration, traefikPointersConfiguration))
 	f.AddCommand(storeconfigCmd)
+	f.AddCommand(healthcheckCmd)
 
 	usedCmd, err := f.GetCommand()
 	if err != nil {

docs/basics.md

@@ -514,6 +514,7 @@ List of Træfik available commands with description :
 - `version` : Print version 
 - `storeconfig` : Store the static traefik configuration into a Key-value stores. Please refer to the [Store Træfik configuration](/user-guide/kv-config/#store-trfk-configuration) section to get documentation on it.
 - `bug`: The easiest way to submit a pre-filled issue.
+- `healthcheck`: Calls traefik `/ping` to check health.
 
 Each command may have related flags.
 All those related flags will be displayed with :
@@ -538,6 +539,18 @@ $ traefik bug
 
 See https://www.youtube.com/watch?v=Lyz62L8m93I.
 
+## Command: healthcheck
+
+This command allows to check the health of Traefik. Its exit status is `0` if Traefik is healthy and `1` if it is unhealthy.
+This can be used with Docker [HEALTHCHECK](https://docs.docker.com/engine/reference/builder/#healthcheck) instruction or any other health check orchestration mechanism.
+
+Note: the `web` provider must be enabled to allow `/ping` calls by the `healthcheck` command.
+
+```bash
+$ traefik healthcheck
+OK: http://:8082/ping
+```
+
 # Log Rotation
 
 Traefik will close and reopen its log files, assuming they're configured, on receipt of a USR1 signal.  This allows the logs

server/web.go

@@ -136,20 +136,27 @@ func (provider *WebProvider) Provide(configurationChan chan<- types.ConfigMessag
 
 	safe.Go(func() {
 		var err error
-		var negroni = negroni.New()
+		var negroniInstance = negroni.New()
 		if provider.Auth != nil {
 			authMiddleware, err := middlewares.NewAuthenticator(provider.Auth)
 			if err != nil {
 				log.Fatal("Error creating Auth: ", err)
 			}
-			negroni.Use(authMiddleware)
+			authMiddlewareWrapper := negroni.HandlerFunc(func(w http.ResponseWriter, r *http.Request, next http.HandlerFunc) {
+				if r.URL.Path == "/ping" {
+					next.ServeHTTP(w, r)
+				} else {
+					authMiddleware.ServeHTTP(w, r, next)
+				}
+			})
+			negroniInstance.Use(authMiddlewareWrapper)
 		}
-		negroni.UseHandler(systemRouter)
+		negroniInstance.UseHandler(systemRouter)
 
 		if len(provider.CertFile) > 0 && len(provider.KeyFile) > 0 {
-			err = http.ListenAndServeTLS(provider.Address, provider.CertFile, provider.KeyFile, negroni)
+			err = http.ListenAndServeTLS(provider.Address, provider.CertFile, provider.KeyFile, negroniInstance)
 		} else {
-			err = http.ListenAndServe(provider.Address, negroni)
+			err = http.ListenAndServe(provider.Address, negroniInstance)
 		}
 
 		if err != nil {