Toggle /ping to artificially return unhealthy response on SIGTERM during requestAcceptGraceTimeout interval

docs/configuration/ping.md

@@ -85,3 +85,7 @@ Note the dedicated port `:8082` for `/ping`.
 
 In the above example, it is _very_ important to create a named dedicated entry point, and do **not** include it in `defaultEntryPoints`.
 Otherwise, you are likely to expose _all_ services via this entry point.
+
+### Using ping for external Load-balancer rotation health check
+
+If you are running traefik behind a external Load-balancer, and want to configure rotation health check on the Load-balancer to take a traefik instance out of rotation gracefully, you can configure [lifecycle.requestAcceptGraceTimeout](/configuration/commons.md#life-cycle) and the ping endpoint will return `503` response on traefik server termination, so that the Load-balancer can take the terminating traefik instance out of rotation, before it stops responding.

integration/basic_test.go

@@ -128,6 +128,10 @@ func (s *SimpleSuite) TestRequestAcceptGraceTimeout(c *check.C) {
 	err = try.GetRequest("http://127.0.0.1:8000/service", 3*time.Second, try.StatusCodeIs(http.StatusOK))
 	c.Assert(err, checker.IsNil)
 
+	// Check that /ping endpoint is responding with 200.
+	err = try.GetRequest("http://127.0.0.1:8001/ping", 3*time.Second, try.StatusCodeIs(http.StatusOK))
+	c.Assert(err, checker.IsNil)
+
 	// Send SIGTERM to Traefik.
 	proc, err := os.FindProcess(cmd.Process.Pid)
 	c.Assert(err, checker.IsNil)
@@ -143,6 +147,12 @@ func (s *SimpleSuite) TestRequestAcceptGraceTimeout(c *check.C) {
 	defer resp.Body.Close()
 	c.Assert(resp.StatusCode, checker.Equals, http.StatusOK)
 
+	// ping endpoint should now return a Service Unavailable.
+	resp, err = http.Get("http://127.0.0.1:8001/ping")
+	c.Assert(err, checker.IsNil)
+	defer resp.Body.Close()
+	c.Assert(resp.StatusCode, checker.Equals, http.StatusServiceUnavailable)
+
 	// Expect Traefik to shut down gracefully once the request accepting grace
 	// period has elapsed.
 	waitErr := make(chan error)

integration/fixtures/reqacceptgrace.toml

@@ -6,6 +6,9 @@ logLevel = "DEBUG"
   [entryPoints.http]
   address = ":8000"
 
+  [entryPoints.traefik]
+  address = ":8001"
+
 [lifeCycle]
   requestAcceptGraceTimeout = "10s"
 
@@ -20,3 +23,5 @@ logLevel = "DEBUG"
   backend = "backend"
     [frontends.frontend.routes.service]
     rule = "Path:/service"
+
+[ping]

ping/ping.go

@@ -3,19 +3,38 @@ package ping
 import (
 	"fmt"
 	"net/http"
+	"sync"
 
 	"github.com/containous/mux"
 )
 
-//Handler expose ping routes
+// Handler expose ping routes
 type Handler struct {
-	EntryPoint string `description:"Ping entryPoint" export:"true"`
+	EntryPoint  string `description:"Ping entryPoint" export:"true"`
+	terminating bool
+	lock        sync.RWMutex
+}
+
+// SetTerminating causes the ping endpoint to serve non 200 responses.
+func (g *Handler) SetTerminating() {
+	g.lock.Lock()
+	defer g.lock.Unlock()
+
+	g.terminating = true
 }
 
 // AddRoutes add ping routes on a router
-func (g Handler) AddRoutes(router *mux.Router) {
+func (g *Handler) AddRoutes(router *mux.Router) {
 	router.Methods(http.MethodGet, http.MethodHead).Path("/ping").
 		HandlerFunc(func(response http.ResponseWriter, request *http.Request) {
-			fmt.Fprint(response, "OK")
+			g.lock.RLock()
+			defer g.lock.RUnlock()
+
+			statusCode := http.StatusOK
+			if g.terminating {
+				statusCode = http.StatusServiceUnavailable
+			}
+			response.WriteHeader(statusCode)
+			fmt.Fprint(response, http.StatusText(statusCode))
 		})
 }

server/server.go

@@ -212,6 +212,9 @@ func (s *Server) StartWithContext(ctx context.Context) {
 		<-ctx.Done()
 		log.Info("I have to go...")
 		reqAcceptGraceTimeOut := time.Duration(s.globalConfiguration.LifeCycle.RequestAcceptGraceTimeout)
+		if s.globalConfiguration.Ping != nil && reqAcceptGraceTimeOut > 0 {
+			s.globalConfiguration.Ping.SetTerminating()
+		}
 		if reqAcceptGraceTimeOut > 0 {
 			log.Infof("Waiting %s for incoming requests to cease", reqAcceptGraceTimeOut)
 			time.Sleep(reqAcceptGraceTimeOut)