NET-9178-Consul-api-gateway-not-starting-after-restart (#3978)

* don't error if role already exists on restart

* changelog

* lint

.changelog/3978.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+connect-inject: Fixed issue where on restart, if a managed-gateway-acl-role already existed the container would error
+```

control-plane/api-gateway/cache/consul.go

@@ -397,6 +397,10 @@ func (c *Cache) ensurePolicy(client *api.Client, gatewayName string) (string, er
 	return existing.ID, nil
 }
 
+func getACLRoleName(gatewayName string) string {
+	return fmt.Sprint("managed-gateway-acl-role-", gatewayName)
+}
+
 func (c *Cache) ensureRole(client *api.Client, gatewayName string) (string, error) {
 	policyID, err := c.ensurePolicy(client, gatewayName)
 	if err != nil {
@@ -407,19 +411,21 @@ func (c *Cache) ensureRole(client *api.Client, gatewayName string) (string, erro
 	defer c.aclRoleMutex.Unlock()
 
 	createRole := func() (string, error) {
-		aclRoleName := fmt.Sprint("managed-gateway-acl-role-", gatewayName)
+		aclRoleName := getACLRoleName(gatewayName)
 		role := &api.ACLRole{
 			Name:        aclRoleName,
 			Description: "ACL Role for Managed API Gateways",
 			Policies:    []*api.ACLLink{{ID: policyID}},
 		}
 
 		_, _, err = client.ACL().RoleCreate(role, &api.WriteOptions{})
-		if err != nil {
+		if err != nil && !isRoleExistsErr(err, aclRoleName) {
+			//don't error out in the case that the role already exists.
 			return "", err
 		}
+
 		c.gatewayNameToRole[gatewayName] = role
-		return aclRoleName, err
+		return aclRoleName, nil
 	}
 
 	cachedRole, found := c.gatewayNameToRole[gatewayName]
@@ -592,7 +598,18 @@ func ignoreACLsDisabled(err error) error {
 // isPolicyExistsErr returns true if err is due to trying to call the
 // policy create API when the policy already exists.
 func isPolicyExistsErr(err error, policyName string) bool {
+	return isExistsErr(err, "Policy", policyName)
+}
+
+// isExistsErr returns true if err is due to trying to call an API for a given type and it already exists.
+func isExistsErr(err error, typeName, name string) bool {
 	return err != nil &&
 		strings.Contains(err.Error(), "Unexpected response code: 500") &&
-		strings.Contains(err.Error(), fmt.Sprintf("Invalid Policy: A Policy with Name %q already exists", policyName))
+		strings.Contains(err.Error(), fmt.Sprintf("Invalid %s: A %s with Name %q already exists", typeName, typeName, name))
+}
+
+// isRoleExistsErr returns true if err is due to trying to call the
+// role create API when the role already exists.
+func isRoleExistsErr(err error, roleName string) bool {
+	return isExistsErr(err, "Role", roleName)
 }