nfd-master: use flag for command line parsing

2024-12-14 11:57:51 +00:00 · 2021-02-19 07:38:55 +02:00 · 2021-02-19 07:38:55 +02:00 · 47033db9c1
commit 47033db9c1
parent a7d0439af6
8 changed files with 171 additions and 205 deletions
--- a/cmd/nfd-master/main.go
+++ b/cmd/nfd-master/main.go
@ -1,5 +1,5 @@
 /*
-Copyright 2019 The Kubernetes Authors.
+Copyright 2019-2021 The Kubernetes Authors.

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@ -17,14 +17,14 @@ limitations under the License.
 package main

 import (
+	"flag"
 	"fmt"
 	"log"
+	"os"
 	"regexp"
-	"strconv"
-	"strings"

-	"github.com/docopt/docopt-go"
 	master "sigs.k8s.io/node-feature-discovery/pkg/nfd-master"
+	"sigs.k8s.io/node-feature-discovery/pkg/utils"
 	"sigs.k8s.io/node-feature-discovery/pkg/version"
 )

@ -34,17 +34,29 @@ const (
 )

 func main() {
+	flags := flag.NewFlagSet(ProgramName, flag.ExitOnError)
+
+	printVersion := flags.Bool("version", false, "Print version and exit.")
+
+	args := initFlags(flags)
+
+	_ = flags.Parse(os.Args[1:])
+	if len(flags.Args()) > 0 {
+		fmt.Printf("unknown command line argument: %s\n", flags.Args()[0])
+		flags.Usage()
+		os.Exit(2)
+	}
+
+	if *printVersion {
+		fmt.Println(ProgramName, version.Get())
+		os.Exit(0)
+	}
+
 	// Assert that the version is known
 	if version.Undefined() {
 		log.Print("WARNING: version not set! Set -ldflags \"-X sigs.k8s.io/node-feature-discovery/pkg/version.version=`git describe --tags --dirty --always`\" during build or run.")
 	}

-	// Parse command-line arguments.
-	args, err := argsParse(nil)
-	if err != nil {
-		log.Fatalf("failed to parse command line: %v", err)
-	}
-
 	// Get new NfdMaster instance
 	instance, err := master.NewNfdMaster(args)
 	if err != nil {
@ -56,88 +68,37 @@ func main() {
 	}
 }

-// argsParse parses the command line arguments passed to the program.
-// The argument argv is passed only for testing purposes.
-func argsParse(argv []string) (master.Args, error) {
-	args := master.Args{}
-	usage := fmt.Sprintf(`%s.
-
-  Usage:
-  %s [--prune] [--no-publish] [--label-whitelist=<pattern>] [--port=<port>]
-     [--ca-file=<path>] [--cert-file=<path>] [--key-file=<path>]
-     [--verify-node-name] [--extra-label-ns=<list>] [--resource-labels=<list>]
-     [--kubeconfig=<path>] [--instance=<name>]
-  %s -h | --help
-  %s --version
-
-  Options:
-  -h --help                       Show this screen.
-  --version                       Output version and exit.
-  --prune                         Prune all NFD related attributes from all nodes
-                                  of the cluster and exit.
-  --instance=<name>               Instance name. Used to separate annotation
-                                  namespaces for multiple parallel deployments.
-                                  [Default: ]
-  --kubeconfig=<path>             Kubeconfig to use [Default: ]
-                                  of the cluster and exit.
-  --port=<port>                   Port on which to listen for connections.
-                                  [Default: 8080]
-  --ca-file=<path>                Root certificate for verifying connections
-                                  [Default: ]
-  --cert-file=<path>              Certificate used for authenticating connections
-                                  [Default: ]
-  --key-file=<path>               Private key matching --cert-file
-                                  [Default: ]
-  --verify-node-name              Verify worker node name against CN from the TLS
-                                  certificate. Only has effect when TLS authentication
-                                  has been enabled.
-  --no-publish                    Do not publish feature labels
-  --label-whitelist=<pattern>     Regular expression to filter label names to
-                                  publish to the Kubernetes API server.
-                                  NB: the label namespace is omitted i.e. the filter
-                                  is only applied to the name part after '/'.
-                                  [Default: ]
-  --extra-label-ns=<list>         Comma separated list of allowed extra label namespaces
-                                  [Default: ]
-  --resource-labels=<list>        Comma separated list of labels to be exposed as extended resources.
-                                  [Default: ]`,
-		ProgramName,
-		ProgramName,
-		ProgramName,
-		ProgramName,
-	)
-
-	arguments, _ := docopt.ParseArgs(usage, argv,
-		fmt.Sprintf("%s %s", ProgramName, version.Get()))
-
-	// Parse argument values as usable types.
-	var err error
-	args.Instance = arguments["--instance"].(string)
-	if ok, _ := regexp.MatchString(`^([A-Za-z0-9][-A-Za-z0-9_.]*)?[A-Za-z0-9]$`, args.Instance); args.Instance != "" && !ok {
-		return args, fmt.Errorf("invalid --instance %q: instance name "+
-			"must start and end with an alphanumeric character and may only contain "+
-			"alphanumerics, `-`, `_` or `.`", args.Instance)
+func initFlags(flagset *flag.FlagSet) *master.Args {
+	args := &master.Args{
+		LabelWhiteList: utils.RegexpVal{Regexp: *regexp.MustCompile("")},
 	}
-	args.CaFile = arguments["--ca-file"].(string)
-	args.CertFile = arguments["--cert-file"].(string)
-	args.KeyFile = arguments["--key-file"].(string)
-	args.NoPublish = arguments["--no-publish"].(bool)
-	args.Port, err = strconv.Atoi(arguments["--port"].(string))
-	if err != nil {
-		return args, fmt.Errorf("invalid --port defined: %s", err)
-	}
-	args.LabelWhiteList, err = regexp.Compile(arguments["--label-whitelist"].(string))
-	if err != nil {
-		return args, fmt.Errorf("error parsing whitelist regex (%s): %s", arguments["--label-whitelist"], err)
-	}
-	args.VerifyNodeName = arguments["--verify-node-name"].(bool)
-	args.ExtraLabelNs = map[string]struct{}{}
-	for _, n := range strings.Split(arguments["--extra-label-ns"].(string), ",") {
-		args.ExtraLabelNs[n] = struct{}{}
-	}
-	args.ResourceLabels = strings.Split(arguments["--resource-labels"].(string), ",")
-	args.Prune = arguments["--prune"].(bool)
-	args.Kubeconfig = arguments["--kubeconfig"].(string)

-	return args, nil
+	flagset.StringVar(&args.CaFile, "ca-file", "",
+		"Root certificate for verifying connections")
+	flagset.StringVar(&args.CertFile, "cert-file", "",
+		"Certificate used for authenticating connections")
+	flagset.Var(&args.ExtraLabelNs, "extra-label-ns",
+		"Comma separated list of allowed extra label namespaces")
+	flagset.StringVar(&args.Instance, "instance", "",
+		"Instance name. Used to separate annotation namespaces for multiple parallel deployments.")
+	flagset.StringVar(&args.KeyFile, "key-file", "",
+		"Private key matching -cert-file")
+	flagset.StringVar(&args.Kubeconfig, "kubeconfig", "",
+		"Kubeconfig to use")
+	flagset.Var(&args.LabelWhiteList, "label-whitelist",
+		"Regular expression to filter label names to publish to the Kubernetes API server. "+
+			"NB: the label namespace is omitted i.e. the filter is only applied to the name part after '/'.")
+	flagset.BoolVar(&args.NoPublish, "no-publish", false,
+		"Do not publish feature labels")
+	flagset.IntVar(&args.Port, "port", 8080,
+		"Port on which to listen for connections.")
+	flagset.BoolVar(&args.Prune, "prune", false,
+		"Prune all NFD related attributes from all nodes of the cluaster and exit.")
+	flagset.Var(&args.ResourceLabels, "resource-labels",
+		"Comma separated list of labels to be exposed as extended resources.")
+	flagset.BoolVar(&args.VerifyNodeName, "verify-node-name", false,
+		"Verify worker node name against CN from the TLS certificate. "+
+			"Only takes effect when TLS authentication has been enabled.")
+
+	return args
 }
--- a/cmd/nfd-master/main_test.go
+++ b/cmd/nfd-master/main_test.go
@ -1,55 +0,0 @@
-/*
-Copyright 2019 The Kubernetes Authors.
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
-*/
-
-package main
-
-import (
-	"testing"
-
-	. "github.com/smartystreets/goconvey/convey"
-)
-
-func TestArgsParse(t *testing.T) {
-	Convey("When parsing command line arguments", t, func() {
-		Convey("When --no-publish and --oneshot flags are passed", func() {
-			args, err := argsParse([]string{"--no-publish"})
-			Convey("noPublish is set and args.sources is set to the default value", func() {
-				So(args.NoPublish, ShouldBeTrue)
-				So(len(args.LabelWhiteList.String()), ShouldEqual, 0)
-				So(err, ShouldBeNil)
-			})
-		})
-
-		Convey("When valid args are specified", func() {
-			args, err := argsParse([]string{"--label-whitelist=.*rdt.*", "--port=1234", "--cert-file=crt", "--key-file=key", "--ca-file=ca"})
-			Convey("Argument parsing should succeed and args set to correct values", func() {
-				So(args.NoPublish, ShouldBeFalse)
-				So(args.Port, ShouldEqual, 1234)
-				So(args.CertFile, ShouldEqual, "crt")
-				So(args.KeyFile, ShouldEqual, "key")
-				So(args.CaFile, ShouldEqual, "ca")
-				So(args.LabelWhiteList.String(), ShouldResemble, ".*rdt.*")
-				So(err, ShouldBeNil)
-			})
-		})
-		Convey("When invalid --port is defined", func() {
-			_, err := argsParse([]string{"--port=123a"})
-			Convey("argsParse should fail", func() {
-				So(err, ShouldNotBeNil)
-			})
-		})
-	})
-}
--- a/docs/advanced/developer-guide.md
+++ b/docs/advanced/developer-guide.md
@ -164,43 +164,34 @@ $ docker run --rm --name=nfd-test ${NFD_CONTAINER_IMAGE} nfd-master --no-publish
 Command line flags of nfd-master:

 ```bash
-$ docker run --rm ${NFD_CONTAINER_IMAGE} nfd-master --help
-...
-Usage:
-  nfd-master [--prune] [--no-publish] [--label-whitelist=<pattern>] [--port=<port>]
-     [--ca-file=<path>] [--cert-file=<path>] [--key-file=<path>]
-     [--verify-node-name] [--extra-label-ns=<list>] [--resource-labels=<list>]
-     [--kubeconfig=<path>]
-  nfd-master -h | --help
-  nfd-master --version
-
-  Options:
-  -h --help                       Show this screen.
-  --version                       Output version and exit.
-  --prune                         Prune all NFD related attributes from all nodes
-                                  of the cluster and exit.
-  --kubeconfig=<path>             Kubeconfig to use [Default: ]
-  --port=<port>                   Port on which to listen for connections.
-                                  [Default: 8080]
-  --ca-file=<path>                Root certificate for verifying connections
-                                  [Default: ]
-  --cert-file=<path>              Certificate used for authenticating connections
-                                  [Default: ]
-  --key-file=<path>               Private key matching --cert-file
-                                  [Default: ]
-  --verify-node-name              Verify worker node name against CN from the TLS
-                                  certificate. Only has effect when TLS authentication
-                                  has been enabled.
-  --no-publish                    Do not publish feature labels
-  --label-whitelist=<pattern>     Regular expression to filter label names to
-                                  publish to the Kubernetes API server.
-                                  NB: the label namespace is omitted i.e. the filter
-                                  is only applied to the name part after '/'.
-                                  [Default: ]
-  --extra-label-ns=<list>         Comma separated list of allowed extra label namespaces
-                                  [Default: ]
-  --resource-labels=<list>        Comma separated list of labels to be exposed as extended resources.
-                                  [Default: ]
+$ docker run --rm ${NFD_CONTAINER_IMAGE} nfd-master -help
+Usage of nfd-master:
+  -ca-file string
+    	Root certificate for verifying connections
+  -cert-file string
+    	Certificate used for authenticating connections
+  -extra-label-ns value
+    	Comma separated list of allowed extra label namespaces
+  -instance string
+    	Instance name. Used to separate annotation namespaces for multiple parallel deployments.
+  -key-file string
+    	Private key matching -cert-file
+  -kubeconfig string
+    	Kubeconfig to use
+  -label-whitelist value
+    	Regular expression to filter label names to publish to the Kubernetes API server. NB: the label namespace is omitted i.e. the filter is only applied to the name part after '/'.
+  -no-publish
+    	Do not publish feature labels
+  -port int
+    	Port on which to listen for connections. (default 8080)
+  -prune
+    	Prune all NFD related attributes from all nodes of the cluaster and exit.
+  -resource-labels value
+    	Comma separated list of labels to be exposed as extended resources.
+  -verify-node-name
+    	Verify worker node name against CN from the TLS certificate. Only takes effect when TLS authentication has been enabled.
+  -version
+    	Print version and exit.
 ```

 ### NFD-Worker
--- a/pkg/nfd-master/nfd-master-internal_test.go
+++ b/pkg/nfd-master/nfd-master-internal_test.go
@ -1,5 +1,5 @@
 /*
-Copyright 2019 The Kubernetes Authors.
+Copyright 2019-2021 The Kubernetes Authors.

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@ -34,6 +34,7 @@ import (
 	k8sclient "k8s.io/client-go/kubernetes"
 	"sigs.k8s.io/node-feature-discovery/pkg/apihelper"
 	"sigs.k8s.io/node-feature-discovery/pkg/labeler"
+	"sigs.k8s.io/node-feature-discovery/pkg/utils"
 	"sigs.k8s.io/node-feature-discovery/pkg/version"
 	"sigs.k8s.io/yaml"
 )
@ -55,7 +56,7 @@ func newMockMaster(apihelper apihelper.APIHelpers) *nfdMaster {
 	return &nfdMaster{
 		nodeName:     mockNodeName,
 		annotationNs: AnnotationNsBase,
-		args:         Args{LabelWhiteList: regexp.MustCompile("")},
+		args:         Args{LabelWhiteList: utils.RegexpVal{Regexp: *regexp.MustCompile("")}},
 		apihelper:    apihelper,
 	}
 }
@ -339,7 +340,7 @@ func TestSetLabels(t *testing.T) {
 				apihelper.NewJsonPatch("add", "/metadata/labels", LabelNs+"/feature-2", mockLabels["feature-2"]),
 			}

-			mockMaster.args.LabelWhiteList = regexp.MustCompile("^f.*2$")
+			mockMaster.args.LabelWhiteList.Regexp = *regexp.MustCompile("^f.*2$")
 			mockHelper.On("GetClient").Return(mockClient, nil)
 			mockHelper.On("GetNode", mockClient, workerName).Return(mockNode, nil)
 			mockHelper.On("PatchNode", mockClient, mockNodeName, mock.MatchedBy(jsonPatchMatcher(expectedPatches))).Return(nil)
@ -390,7 +391,7 @@ func TestSetLabels(t *testing.T) {
 				apihelper.NewJsonPatch("add", "/status/capacity", LabelNs+"/feature-3", mockLabels["feature-3"]),
 			}

-			mockMaster.args.ResourceLabels = []string{"feature-3", "feature-1"}
+			mockMaster.args.ResourceLabels = map[string]struct{}{"feature-3": struct{}{}, "feature-1": struct{}{}}
 			mockHelper.On("GetClient").Return(mockClient, nil)
 			mockHelper.On("GetNode", mockClient, workerName).Return(mockNode, nil)
 			mockHelper.On("PatchNode", mockClient, mockNodeName, mock.MatchedBy(jsonPatchMatcher(expectedPatches))).Return(nil)
--- a/pkg/nfd-master/nfd-master.go
+++ b/pkg/nfd-master/nfd-master.go
@ -1,5 +1,5 @@
 /*
-Copyright 2019 The Kubernetes Authors.
+Copyright 2019-2021 The Kubernetes Authors.

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@ -38,6 +38,7 @@ import (
 	api "k8s.io/api/core/v1"
 	"sigs.k8s.io/node-feature-discovery/pkg/apihelper"
 	pb "sigs.k8s.io/node-feature-discovery/pkg/labeler"
+	"sigs.k8s.io/node-feature-discovery/pkg/utils"
 	"sigs.k8s.io/node-feature-discovery/pkg/version"
 )

@ -74,16 +75,16 @@ type Annotations map[string]string
 type Args struct {
 	CaFile         string
 	CertFile       string
-	ExtraLabelNs   map[string]struct{}
+	ExtraLabelNs   utils.StringSetVal
 	Instance       string
 	KeyFile        string
 	Kubeconfig     string
-	LabelWhiteList *regexp.Regexp
+	LabelWhiteList utils.RegexpVal
 	NoPublish      bool
 	Port           int
 	Prune          bool
 	VerifyNodeName bool
-	ResourceLabels []string
+	ResourceLabels utils.StringSetVal
 }

 type NfdMaster interface {
@ -102,8 +103,8 @@ type nfdMaster struct {
 }

 // Create new NfdMaster server instance.
-func NewNfdMaster(args Args) (NfdMaster, error) {
-	nfd := &nfdMaster{args: args,
+func NewNfdMaster(args *Args) (NfdMaster, error) {
+	nfd := &nfdMaster{args: *args,
 		nodeName: os.Getenv("NODE_NAME"),
 		ready:    make(chan bool, 1),
 	}
@ -111,6 +112,11 @@ func NewNfdMaster(args Args) (NfdMaster, error) {
 	if args.Instance == "" {
 		nfd.annotationNs = AnnotationNsBase
 	} else {
+		if ok, _ := regexp.MatchString(`^([A-Za-z0-9][-A-Za-z0-9_.]*)?[A-Za-z0-9]$`, args.Instance); !ok {
+			return nfd, fmt.Errorf("invalid --instance %q: instance name "+
+				"must start and end with an alphanumeric character and may only contain "+
+				"alphanumerics, `-`, `_` or `.`", args.Instance)
+		}
 		nfd.annotationNs = args.Instance + "." + AnnotationNsBase
 	}

@ -283,7 +289,7 @@ func (m *nfdMaster) updateMasterNode() error {
 // into extended resources. This function also handles proper namespacing of
 // labels and ERs, i.e. adds the possibly missing default namespace for labels
 // arriving through the gRPC API.
-func filterFeatureLabels(labels Labels, extraLabelNs map[string]struct{}, labelWhiteList *regexp.Regexp, extendedResourceNames []string) (Labels, ExtendedResources) {
+func filterFeatureLabels(labels Labels, extraLabelNs map[string]struct{}, labelWhiteList regexp.Regexp, extendedResourceNames map[string]struct{}) (Labels, ExtendedResources) {
 	outLabels := Labels{}

 	for label, value := range labels {
@ -310,7 +316,7 @@ func filterFeatureLabels(labels Labels, extraLabelNs map[string]struct{}, labelW

 	// Remove labels which are intended to be extended resources
 	extendedResources := ExtendedResources{}
-	for _, extendedResourceName := range extendedResourceNames {
+	for extendedResourceName := range extendedResourceNames {
 		// Add possibly missing default ns
 		extendedResourceName = addNs(extendedResourceName, LabelNs)
 		if value, ok := outLabels[extendedResourceName]; ok {
@ -354,7 +360,7 @@ func (m *nfdMaster) SetLabels(c context.Context, r *pb.SetLabelsRequest) (*pb.Se
 	}
 	stdoutLogger.Printf("REQUEST Node: %s NFD-version: %s Labels: %s", r.NodeName, r.NfdVersion, r.Labels)

-	labels, extendedResources := filterFeatureLabels(r.Labels, m.args.ExtraLabelNs, m.args.LabelWhiteList, m.args.ResourceLabels)
+	labels, extendedResources := filterFeatureLabels(r.Labels, m.args.ExtraLabelNs, m.args.LabelWhiteList.Regexp, m.args.ResourceLabels)

 	if !m.args.NoPublish {
 		// Advertise NFD worker version as an annotation
--- a/pkg/nfd-master/nfd-master_test.go
+++ b/pkg/nfd-master/nfd-master_test.go
@ -1,5 +1,5 @@
 /*
-Copyright 2019 The Kubernetes Authors.
+Copyright 2019-2021 The Kubernetes Authors.

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@ -26,9 +26,9 @@ import (
 func TestNewNfdMaster(t *testing.T) {
 	Convey("When initializing new NfdMaster instance", t, func() {
 		Convey("When one of --cert-file, --key-file or --ca-file is missing", func() {
-			_, err := m.NewNfdMaster(m.Args{CertFile: "crt", KeyFile: "key"})
-			_, err2 := m.NewNfdMaster(m.Args{KeyFile: "key", CaFile: "ca"})
-			_, err3 := m.NewNfdMaster(m.Args{CertFile: "crt", CaFile: "ca"})
+			_, err := m.NewNfdMaster(&m.Args{CertFile: "crt", KeyFile: "key"})
+			_, err2 := m.NewNfdMaster(&m.Args{KeyFile: "key", CaFile: "ca"})
+			_, err3 := m.NewNfdMaster(&m.Args{CertFile: "crt", CaFile: "ca"})
 			Convey("An error should be returned", func() {
 				So(err, ShouldNotBeNil)
 				So(err2, ShouldNotBeNil)
--- a/pkg/nfd-worker/nfd-worker_test.go
+++ b/pkg/nfd-worker/nfd-worker_test.go
@ -34,11 +34,11 @@ type testContext struct {
 	errs   chan error
 }

-func setupTest(args nfdmaster.Args) testContext {
+func setupTest(args *nfdmaster.Args) testContext {
 	// Fixed port and no-publish, for convenience
 	args.NoPublish = true
 	args.Port = 8192
-	args.LabelWhiteList = regexp.MustCompile("")
+	args.LabelWhiteList.Regexp = *regexp.MustCompile("")
 	m, err := nfdmaster.NewNfdMaster(args)
 	if err != nil {
 		fmt.Printf("Test setup failed: %v\n", err)
@ -86,7 +86,7 @@ func TestNewNfdWorker(t *testing.T) {
 }

 func TestRun(t *testing.T) {
-	ctx := setupTest(nfdmaster.Args{})
+	ctx := setupTest(&nfdmaster.Args{})
 	defer teardownTest(ctx)
 	Convey("When running nfd-worker against nfd-master", t, func() {
 		Convey("When publishing features from fake source", func() {
@ -100,7 +100,7 @@ func TestRun(t *testing.T) {
 }

 func TestRunTls(t *testing.T) {
-	masterArgs := nfdmaster.Args{
+	masterArgs := &nfdmaster.Args{
 		CaFile:         data.FilePath("ca.crt"),
 		CertFile:       data.FilePath("nfd-test-master.crt"),
 		KeyFile:        data.FilePath("nfd-test-master.key"),
--- a/pkg/utils/flags.go
+++ b/pkg/utils/flags.go
@ -0,0 +1,62 @@
+/*
+Copyright 2021 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package utils
+
+import (
+	"regexp"
+	"sort"
+	"strings"
+)
+
+// RegexpVal is a wrapper for regexp command line flags
+type RegexpVal struct {
+	regexp.Regexp
+}
+
+// Set implements the flag.Value interface
+func (a *RegexpVal) Set(val string) error {
+	r, err := regexp.Compile(val)
+	a.Regexp = *r
+	return err
+}
+
+// StringSetVal is a Value encapsulating a set of comma-separated strings
+type StringSetVal map[string]struct{}
+
+// Set implements the flag.Value interface
+func (a *StringSetVal) Set(val string) error {
+	m := map[string]struct{}{}
+	for _, n := range strings.Split(val, ",") {
+		m[n] = struct{}{}
+	}
+	*a = m
+	return nil
+}
+
+// String implements the flag.Value interface
+func (a *StringSetVal) String() string {
+	if *a == nil {
+		return ""
+	}
+
+	vals := make([]string, len(*a), 0)
+	for val := range *a {
+		vals = append(vals, val)
+	}
+	sort.Strings(vals)
+	return strings.Join(vals, ",")
+}