Fix unsound behavior

The IP-Per-Task feature changed the behavior for
clients without this configuration (using the task IP instead
of task hostname). This patch make the new behavior available
just for Mesos installation with IP-Per-Task enabled. It also
make it possible to force the use of task's hostname.

docs/toml.md

@@ -969,6 +969,16 @@ domain = "marathon.localhost"
 # Default: "10s"
 #
 # keepAlive = "10s"
+
+# By default, a task's IP address (as returned by the Marathon API) is used as 
+# backend server if an IP-per-task configuration can be found; otherwise, the
+# name of the host running the task is used.
+# The latter behavior can be enforced by enabling this switch.
+# 
+# Optional
+# Default: false
+#
+# forceTaskHostname: false 
 ```
 
 Labels can be used on containers to override default behaviour:

provider/marathon/marathon.go

@@ -42,6 +42,7 @@ type Provider struct {
 	TLS                     *provider.ClientTLS `description:"Enable Docker TLS support"`
 	DialerTimeout           flaeg.Duration      `description:"Set a non-default connection timeout for Marathon"`
 	KeepAlive               flaeg.Duration      `description:"Set a non-default TCP Keep Alive time in seconds"`
+	ForceTaskHostname       bool                `description:"Force to use the task IP hostname."`
 	Basic                   *Basic
 	marathonClient          marathon.Marathon
 }
@@ -526,11 +527,15 @@ func (p *Provider) getBackendServer(task marathon.Task, applications []marathon.
 		log.Errorf("Unable to get marathon application from task %s", task.AppID)
 		return ""
 	}
-	if len(task.IPAddresses) == 0 {
+	switch {
+	case application.IPAddressPerTask == nil || p.ForceTaskHostname:
+		return task.Host
+	case len(task.IPAddresses) == 0:
+		log.Errorf("Missing marathon IPAddress from task %s", task.AppID)
 		return ""
-	} else if len(task.IPAddresses) == 1 {
+	case len(task.IPAddresses) == 1:
 		return task.IPAddresses[0].IPAddress
-	} else {
+	default:
 		ipAddressIdxStr, ok := p.getLabel(application, "traefik.ipAddressIdx")
 		if !ok {
 			log.Errorf("Unable to get marathon IPAddress from task %s", task.AppID)

provider/marathon/marathon_test.go

@@ -1,10 +1,13 @@
 package marathon
 
 import (
+	"encoding/json"
 	"errors"
 	"reflect"
 	"testing"
 
+	"fmt"
+
 	"github.com/containous/traefik/mocks"
 	"github.com/containous/traefik/testhelpers"
 	"github.com/containous/traefik/types"
@@ -108,7 +111,7 @@ func TestMarathonLoadConfig(t *testing.T) {
 				"backend-test": {
 					Servers: map[string]types.Server{
 						"server-test": {
-							URL:    "http://127.0.0.1:80",
+							URL:    "http://localhost:80",
 							Weight: 0,
 						},
 					},
@@ -161,7 +164,7 @@ func TestMarathonLoadConfig(t *testing.T) {
 				"backend-testLoadBalancerAndCircuitBreaker.dot": {
 					Servers: map[string]types.Server{
 						"server-testLoadBalancerAndCircuitBreaker-dot": {
-							URL:    "http://127.0.0.1:80",
+							URL:    "http://localhost:80",
 							Weight: 0,
 						},
 					},
@@ -219,7 +222,7 @@ func TestMarathonLoadConfig(t *testing.T) {
 				"backend-testMaxConn": {
 					Servers: map[string]types.Server{
 						"server-testMaxConn": {
-							URL:    "http://127.0.0.1:80",
+							URL:    "http://localhost:80",
 							Weight: 0,
 						},
 					},
@@ -274,7 +277,7 @@ func TestMarathonLoadConfig(t *testing.T) {
 				"backend-testMaxConnOnlySpecifyAmount": {
 					Servers: map[string]types.Server{
 						"server-testMaxConnOnlySpecifyAmount": {
-							URL:    "http://127.0.0.1:80",
+							URL:    "http://localhost:80",
 							Weight: 0,
 						},
 					},
@@ -326,7 +329,7 @@ func TestMarathonLoadConfig(t *testing.T) {
 				"backend-testMaxConnOnlyExtractorFunc": {
 					Servers: map[string]types.Server{
 						"server-testMaxConnOnlyExtractorFunc": {
-							URL:    "http://127.0.0.1:80",
+							URL:    "http://localhost:80",
 							Weight: 0,
 						},
 					},
@@ -337,27 +340,37 @@ func TestMarathonLoadConfig(t *testing.T) {
 	}
 
 	for _, c := range cases {
-		fakeClient := newFakeClient(c.applicationsError, c.applications, c.tasksError, c.tasks)
+		appID := ""
-		provider := &Provider{
+		if len(c.applications.Apps) > 0 {
-			Domain:           "docker.localhost",
+			appID = c.applications.Apps[0].ID
-			ExposedByDefault: true,
-			marathonClient:   fakeClient,
 		}
-		actualConfig := provider.loadMarathonConfig()
+		t.Run(fmt.Sprintf("Running case: %s", appID), func(t *testing.T) {
-		fakeClient.AssertExpectations(t)
+			fakeClient := newFakeClient(c.applicationsError, c.applications, c.tasksError, c.tasks)
-		if c.expectedNil {
+			provider := &Provider{
-			if actualConfig != nil {
+				Domain:           "docker.localhost",
-				t.Fatalf("Should have been nil, got %v", actualConfig)
+				ExposedByDefault: true,
+				marathonClient:   fakeClient,
 			}
-		} else {
+			actualConfig := provider.loadMarathonConfig()
-			// Compare backends
+			fakeClient.AssertExpectations(t)
-			if !reflect.DeepEqual(actualConfig.Backends, c.expectedBackends) {
+			if c.expectedNil {
-				t.Fatalf("expected %#v, got %#v", c.expectedBackends, actualConfig.Backends)
+				if actualConfig != nil {
+					t.Fatalf("Should have been nil, got %v", actualConfig)
+				}
+			} else {
+				// Compare backends
+				if !reflect.DeepEqual(actualConfig.Backends, c.expectedBackends) {
+					expected, _ := json.Marshal(c.expectedBackends)
+					actual, _ := json.Marshal(actualConfig.Backends)
+					t.Fatalf("expected\t %s\n, \tgot %s\n", expected, actual)
+				}
+				if !reflect.DeepEqual(actualConfig.Frontends, c.expectedFrontends) {
+					expected, _ := json.Marshal(c.expectedFrontends)
+					actual, _ := json.Marshal(actualConfig.Frontends)
+					t.Fatalf("expected\t %s\n, got\t %s\n", expected, actual)
+				}
 			}
-			if !reflect.DeepEqual(actualConfig.Frontends, c.expectedFrontends) {
+		})
-				t.Fatalf("expected %#v, got %#v", c.expectedFrontends, actualConfig.Frontends)
-			}
-		}
 	}
 }
 
@@ -1451,3 +1464,76 @@ func TestMarathonGetSubDomain(t *testing.T) {
 		}
 	}
 }
+
+func TestGetBackendServer(t *testing.T) {
+
+	applications := []struct {
+		forceTaskHostname bool
+		application       marathon.Application
+		expected          string
+	}{
+		{
+			application: marathon.Application{
+				ID: "app-without-IP-per-task",
+			},
+			expected: "sample.com",
+		},
+		{
+			application: marathon.Application{
+
+				ID: "app-with-IP-per-task",
+				IPAddressPerTask: &marathon.IPAddressPerTask{
+					Discovery: &marathon.Discovery{
+						Ports: &[]marathon.Port{
+							{
+								Number: 8880,
+								Name:   "p1",
+							},
+						},
+					},
+				},
+			},
+			expected: "192.168.0.1",
+		}, {
+			forceTaskHostname: true,
+			application: marathon.Application{
+				ID: "app-with-hostname-enforced",
+				IPAddressPerTask: &marathon.IPAddressPerTask{
+					Discovery: &marathon.Discovery{
+						Ports: &[]marathon.Port{
+							{
+								Number: 8880,
+								Name:   "p1",
+							},
+						},
+					},
+				},
+			},
+			expected: "sample.com",
+		},
+	}
+
+	for _, app := range applications {
+		t.Run(fmt.Sprintf("running %s", app.application.ID), func(t *testing.T) {
+			provider := &Provider{}
+			provider.ForceTaskHostname = app.forceTaskHostname
+
+			applications := []marathon.Application{app.application}
+
+			task := marathon.Task{
+				AppID: app.application.ID,
+				Host:  "sample.com",
+				IPAddresses: []*marathon.IPAddress{
+					{
+						IPAddress: "192.168.0.1",
+					},
+				},
+			}
+
+			actual := provider.getBackendServer(task, applications)
+			if actual != app.expected {
+				t.Errorf("App %s, expected %q, got %q", task.AppID, app.expected, actual)
+			}
+		})
+	}
+}

traefik.sample.toml

@@ -599,6 +599,16 @@
 #
 # keepAlive = "10s"
 
+# By default, a task's IP address (as returned by the Marathon API) is used as 
+# backend server if an IP-per-task configuration can be found; otherwise, the
+# name of the host running the task is used.
+# The latter behavior can be enforced by enabling this switch.
+# 
+# Optional
+# Default: false
+#
+# forceTaskHostname: false 
+
 ################################################################
 # Mesos configuration backend
 ################################################################