provider/google: allow session affinity for compute_backend_service

Google's Backend Services gives users control over the session affinity modes.
Let's allow Terraform users to leverage this option.
We don't change the default value ("NONE", as provided by Google).

resource_compute_backend_service.go

@@ -128,6 +128,12 @@ func resourceComputeBackendService() *schema.Resource {
 				Computed: true,
 			},
 
+			"session_affinity": &schema.Schema{
+				Type:     schema.TypeString,
+				Optional: true,
+				Computed: true,
+			},
+
 			"timeout_sec": &schema.Schema{
 				Type:     schema.TypeInt,
 				Optional: true,
@@ -167,6 +173,10 @@ func resourceComputeBackendServiceCreate(d *schema.ResourceData, meta interface{
 		service.Protocol = v.(string)
 	}
 
+	if v, ok := d.GetOk("session_affinity"); ok {
+		service.SessionAffinity = v.(string)
+	}
+
 	if v, ok := d.GetOk("timeout_sec"); ok {
 		service.TimeoutSec = int64(v.(int))
 	}
@@ -225,6 +235,7 @@ func resourceComputeBackendServiceRead(d *schema.ResourceData, meta interface{})
 	d.Set("enable_cdn", service.EnableCDN)
 	d.Set("port_name", service.PortName)
 	d.Set("protocol", service.Protocol)
+	d.Set("session_affinity", service.SessionAffinity)
 	d.Set("timeout_sec", service.TimeoutSec)
 	d.Set("fingerprint", service.Fingerprint)
 	d.Set("self_link", service.SelfLink)
@@ -272,6 +283,10 @@ func resourceComputeBackendServiceUpdate(d *schema.ResourceData, meta interface{
 		service.TimeoutSec = int64(v.(int))
 	}
 
+	if d.HasChange("session_affinity") {
+		service.SessionAffinity = d.Get("session_affinity").(string)
+	}
+
 	if d.HasChange("enable_cdn") {
 		service.EnableCDN = d.Get("enable_cdn").(bool)
 	}

resource_compute_backend_service_test.go

@@ -187,6 +187,40 @@ func TestAccComputeBackendService_withCDNEnabled(t *testing.T) {
 	}
 }
 
+func TestAccComputeBackendService_withSessionAffinity(t *testing.T) {
+	serviceName := fmt.Sprintf("tf-test-%s", acctest.RandString(10))
+	checkName := fmt.Sprintf("tf-test-%s", acctest.RandString(10))
+	var svc compute.BackendService
+
+	resource.Test(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t) },
+		Providers:    testAccProviders,
+		CheckDestroy: testAccCheckComputeBackendServiceDestroy,
+		Steps: []resource.TestStep{
+			resource.TestStep{
+				Config: testAccComputeBackendService_withSessionAffinity(
+					serviceName, checkName, "CLIENT_IP"),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckComputeBackendServiceExists(
+						"google_compute_backend_service.foobar", &svc),
+				),
+			},
+			resource.TestStep{
+				Config: testAccComputeBackendService_withSessionAffinity(
+					serviceName, checkName, "GENERATED_COOKIE"),
+				Check: resource.ComposeTestCheckFunc(
+					testAccCheckComputeBackendServiceExists(
+						"google_compute_backend_service.foobar", &svc),
+				),
+			},
+		},
+	})
+
+	if svc.SessionAffinity != "GENERATED_COOKIE" {
+		t.Errorf("Expected SessionAffinity == \"GENERATED_COOKIE\", got %t", svc.SessionAffinity)
+	}
+}
+
 func testAccComputeBackendService_basic(serviceName, checkName string) string {
 	return fmt.Sprintf(`
 resource "google_compute_backend_service" "foobar" {
@@ -291,3 +325,20 @@ resource "google_compute_http_health_check" "default" {
 }
 `, serviceName, timeout, igName, itName, checkName)
 }
+
+func testAccComputeBackendService_withSessionAffinity(serviceName, checkName, affinityName string) string {
+	return fmt.Sprintf(`
+resource "google_compute_backend_service" "foobar" {
+  name             = "%s"
+  health_checks    = ["${google_compute_http_health_check.zero.self_link}"]
+  session_affinity = "%s"
+}
+
+resource "google_compute_http_health_check" "zero" {
+  name               = "%s"
+  request_path       = "/"
+  check_interval_sec = 1
+  timeout_sec        = 1
+}
+`, serviceName, affinityName, checkName)
+}