VAULT-6368 Metrics-only listener for Agent (#18101)

* VAULT-6368 Metrics-only listener for Agent

* VAULT-6368 changelog

* VAULT-6368 Update config to use string instead of bool

* VAULT-6368 Fix leftover code

* VAULT-6368 Fix changelog

* VAULT-6368 fix typo

* VAULT-6368 recommended doc update

* VAULT-6368 use != over !(==)

internalshared/configutil/config.go

@@ -2,7 +2,6 @@ package configutil
 
 import (
 	"fmt"
-	"io/ioutil"
 	"time"
 
 	"github.com/hashicorp/go-secure-stdlib/parseutil"
@@ -47,25 +46,6 @@ type SharedConfig struct {
 	ClusterName string `hcl:"cluster_name"`
 }
 
-// LoadConfigFile loads the configuration from the given file.
-func LoadConfigFile(path string) (*SharedConfig, error) {
-	// Read the file
-	d, err := ioutil.ReadFile(path)
-	if err != nil {
-		return nil, err
-	}
-	return ParseConfig(string(d))
-}
-
-func LoadConfigKMSes(path string) ([]*KMS, error) {
-	// Read the file
-	d, err := ioutil.ReadFile(path)
-	if err != nil {
-		return nil, err
-	}
-	return ParseKMSes(string(d))
-}
-
 func ParseConfig(d string) (*SharedConfig, error) {
 	// Parse!
 	obj, err := hcl.Parse(d)

internalshared/configutil/listener.go

@@ -44,6 +44,7 @@ type Listener struct {
 	Type       string
 	Purpose    []string    `hcl:"-"`
 	PurposeRaw interface{} `hcl:"purpose"`
+	Role       string      `hcl:"role"`
 
 	Address                 string        `hcl:"address"`
 	ClusterAddress          string        `hcl:"cluster_address"`
@@ -182,6 +183,13 @@ func ParseListeners(result *SharedConfig, list *ast.ObjectList) error {
 
 				l.PurposeRaw = nil
 			}
+
+			switch l.Role {
+			case "default", "metrics_only", "":
+				result.found(l.Type, l.Type)
+			default:
+				return multierror.Prefix(fmt.Errorf("unsupported listener role %q", l.Role), fmt.Sprintf("listeners.%d:", i))
+			}
 		}
 
 		// Request Parameters