nomad: build dynamic port for exposed checks if not specified (#7800)

nomad/job_endpoint_hook_expose_check.go

@@ -1,9 +1,11 @@
 package nomad
 
 import (
+	"fmt"
 	"strconv"
 	"strings"
 
+	"github.com/hashicorp/nomad/helper/uuid"
 	"github.com/hashicorp/nomad/nomad/structs"
 	"github.com/pkg/errors"
 )
@@ -197,6 +199,21 @@ func exposePathForCheck(tg *structs.TaskGroup, s *structs.Service, check *struct
 		return nil, nil
 	}
 
+	// If the check is exposable but doesn't have a port label set build
+	// a port with a generated label, add it to the group's Dynamic ports
+	// and set the check port label to the generated label.
+	//
+	// This lets PortLabel be optional for any exposed check.
+	if check.PortLabel == "" {
+		port := structs.Port{
+			Label: fmt.Sprintf("svc_%s_ck_%s", s.Name, uuid.Generate()[:6]),
+			To:    -1,
+		}
+
+		tg.Networks[0].DynamicPorts = append(tg.Networks[0].DynamicPorts, port)
+		check.PortLabel = port.Label
+	}
+
 	// Determine the local service port (i.e. what port the service is actually
 	// listening to inside the network namespace).
 	//
@@ -216,9 +233,7 @@ func exposePathForCheck(tg *structs.TaskGroup, s *structs.Service, check *struct
 	}
 
 	// The Path, Protocol, and PortLabel are just copied over from the service
-	// check definition. It is required that the user configure their own port
-	// mapping for each check, including setting the 'to = -1' sentinel value
-	// enabling the network namespace pass-through.
+	// check definition.
 	return &structs.ConsulExposePath{
 		Path:          check.Path,
 		Protocol:      check.Protocol,

nomad/job_endpoint_hook_expose_check_test.go

@@ -346,6 +346,36 @@ func TestJobExposeCheckHook_exposePathForCheck(t *testing.T) {
 		}, s, c)
 		require.EqualError(t, err, `unable to determine local service port for service check group1->service1->check1`)
 	})
+
+	t.Run("empty check port", func(t *testing.T) {
+		c := &structs.ServiceCheck{
+			Name: "check1",
+			Type: "http",
+			Path: "/health",
+		}
+		s := &structs.Service{
+			Name:      "service1",
+			PortLabel: "9999",
+			Checks:    []*structs.ServiceCheck{c},
+		}
+		tg := &structs.TaskGroup{
+			Name:     "group1",
+			Services: []*structs.Service{s},
+			Networks: structs.Networks{{
+				Mode:         "bridge",
+				DynamicPorts: []structs.Port{},
+			}},
+		}
+		ePath, err := exposePathForCheck(tg, s, c)
+		require.NoError(t, err)
+		require.Len(t, tg.Networks[0].DynamicPorts, 1)
+		require.Equal(t, &structs.ConsulExposePath{
+			Path:          "/health",
+			Protocol:      "",
+			LocalPathPort: 9999,
+			ListenerPort:  tg.Networks[0].DynamicPorts[0].Label,
+		}, ePath)
+	})
 }
 
 func TestJobExposeCheckHook_containsExposePath(t *testing.T) {