services: enable setting arbitrary address value in service registrat…

…ions

This PR introduces the `address` field in the `service` block so that Nomad
or Consul services can be registered with a custom `.Address.` to advertise.

The address can be an IP address or domain name. If the `address` field is
set, the `service.address_mode` must be set in `auto` mode.

.changelog/12720.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+services: Enable setting arbitrary address on Nomad or Consul service registration
+```

api/services.go

@@ -86,7 +86,6 @@ type ServiceRegistrationStub struct {
 	Tags []string
 }
 
-
 // Services is used to query the service endpoints.
 type Services struct {
 	client *Client
@@ -195,10 +194,8 @@ func (c *CheckRestart) Merge(o *CheckRestart) *CheckRestart {
 	return nc
 }
 
-// ServiceCheck represents the consul health check that Nomad registers.
+// ServiceCheck represents a Nomad job-submitters view of a Consul service health check.
 type ServiceCheck struct {
-	//FIXME Id is unused. Remove?
-	Id                     string              `hcl:"id,optional"`
 	Name                   string              `hcl:"name,optional"`
 	Type                   string              `hcl:"type,optional"`
 	Command                string              `hcl:"command,optional"`
@@ -208,6 +205,7 @@ type ServiceCheck struct {
 	PortLabel              string              `mapstructure:"port" hcl:"port,optional"`
 	Expose                 bool                `hcl:"expose,optional"`
 	AddressMode            string              `mapstructure:"address_mode" hcl:"address_mode,optional"`
+	Advertise              string              `hcl:"advertise,optional"`
 	Interval               time.Duration       `hcl:"interval,optional"`
 	Timeout                time.Duration       `hcl:"timeout,optional"`
 	InitialStatus          string              `mapstructure:"initial_status" hcl:"initial_status,optional"`
@@ -224,16 +222,15 @@ type ServiceCheck struct {
 	OnUpdate               string              `mapstructure:"on_update" hcl:"on_update,optional"`
 }
 
-// Service represents a Consul service definition.
+// Service represents a Nomad job-submitters view of a Consul or Nomad service.
 type Service struct {
-	//FIXME Id is unused. Remove?
-	Id                string            `hcl:"id,optional"`
 	Name              string            `hcl:"name,optional"`
 	Tags              []string          `hcl:"tags,optional"`
 	CanaryTags        []string          `mapstructure:"canary_tags" hcl:"canary_tags,optional"`
 	EnableTagOverride bool              `mapstructure:"enable_tag_override" hcl:"enable_tag_override,optional"`
 	PortLabel         string            `mapstructure:"port" hcl:"port,optional"`
 	AddressMode       string            `mapstructure:"address_mode" hcl:"address_mode,optional"`
+	Address           string            `hcl:"address,optional"`
 	Checks            []ServiceCheck    `hcl:"check,block"`
 	CheckRestart      *CheckRestart     `mapstructure:"check_restart" hcl:"check_restart,block"`
 	Connect           *ConsulConnect    `hcl:"connect,block"`
@@ -242,9 +239,8 @@ type Service struct {
 	TaskName          string            `mapstructure:"task" hcl:"task,optional"`
 	OnUpdate          string            `mapstructure:"on_update" hcl:"on_update,optional"`
 
-	// Provider defines which backend system provides the service registration
-	// mechanism for this service. This supports either structs.ProviderConsul
-	// or structs.ProviderNomad and defaults for the former.
+	// Provider defines which backend system provides the service registration,
+	// either "consul" (default) or "nomad".
 	Provider string `hcl:"provider,optional"`
 }
 

client/serviceregistration/address.go

@@ -8,22 +8,49 @@ import (
 	"github.com/hashicorp/nomad/plugins/drivers"
 )
 
-// GetAddress returns the IP and port to use for a service or check. If no port
-// label is specified (an empty value), zero values are returned because no
-// address could be resolved.
+// GetAddress returns the IP (or custom advertise address) and port to use for a
+// service or check registration. If no port label is specified (an empty value),
+// zero values are returned because no address could be resolved.
 func GetAddress(
-	addrMode, portLabel string, networks structs.Networks, driverNet *drivers.DriverNetwork,
-	ports structs.AllocatedPorts, netStatus *structs.AllocNetworkStatus) (string, int, error) {
-
-	switch addrMode {
+	address, // custom address, if set
+	addressMode,
+	portLabel string,
+	networks structs.Networks,
+	driverNet *drivers.DriverNetwork,
+	ports structs.AllocatedPorts,
+	netStatus *structs.AllocNetworkStatus,
+) (string, int, error) {
+	switch addressMode {
 	case structs.AddressModeAuto:
-		if driverNet.Advertise() {
-			addrMode = structs.AddressModeDriver
-		} else {
-			addrMode = structs.AddressModeHost
+		switch {
+		case address != "":
+			// No port no problem, just return the advertise address.
+			if portLabel == "" {
+				return address, 0, nil
+			}
+			// A custom advertise address can be used with a port map; using the
+			// Value and ignoring the IP. The routing from your custom address to
+			// the group network address is DIY.
+			if mapping, exists := ports.Get(portLabel); exists {
+				return address, mapping.Value, nil
+			}
+			// If not a port map we can interpolate a numeric port for you.
+			port, err := strconv.Atoi(portLabel)
+			if err != nil {
+				return "", 0, fmt.Errorf("invalid port: %q: not a valid port mapping or numeric port", portLabel)
+			}
+			return address, port, nil
+		case driverNet.Advertise():
+			return GetAddress("", structs.AddressModeDriver, portLabel, networks, driverNet, ports, netStatus)
+		default:
+			return GetAddress("", structs.AddressModeHost, portLabel, networks, driverNet, ports, netStatus)
 		}
-		return GetAddress(addrMode, portLabel, networks, driverNet, ports, netStatus)
 	case structs.AddressModeHost:
+		// Cannot use address mode host with custom advertise address.
+		if address != "" {
+			return "", 0, fmt.Errorf("cannot use custom advertise address with %q address mode", structs.AddressModeHost)
+		}
+
 		if portLabel == "" {
 			if len(networks) != 1 {
 				// If no networks are specified return zero
@@ -32,7 +59,6 @@ func GetAddress(
 				// some people rely on.
 				return "", 0, nil
 			}
-
 			return networks[0].IP, 0, nil
 		}
 
@@ -65,6 +91,11 @@ func GetAddress(
 		return mapping.HostIP, mapping.Value, nil
 
 	case structs.AddressModeDriver:
+		// Cannot use address mode driver with custom advertise address.
+		if address != "" {
+			return "", 0, fmt.Errorf("cannot use custom advertise address with %q address mode", structs.AddressModeDriver)
+		}
+
 		// Require a driver network if driver address mode is used
 		if driverNet == nil {
 			return "", 0, fmt.Errorf(`cannot use address_mode="driver": no driver network exists`)
@@ -100,6 +131,12 @@ func GetAddress(
 		return driverNet.IP, port, nil
 
 	case structs.AddressModeAlloc:
+		// Cannot use address mode alloc with custom advertise address.
+		if address != "" {
+			return "", 0, fmt.Errorf("cannot use custom advertise address with %q address mode", structs.AddressModeAlloc)
+		}
+
+		// Going to need a network for this.
 		if netStatus == nil {
 			return "", 0, fmt.Errorf(`cannot use address_mode="alloc": no allocation network status reported`)
 		}
@@ -131,6 +168,6 @@ func GetAddress(
 
 	default:
 		// Shouldn't happen due to validation, but enforce invariants
-		return "", 0, fmt.Errorf("invalid address mode %q", addrMode)
+		return "", 0, fmt.Errorf("invalid address mode %q", addressMode)
 	}
 }