cmd/swarm/swarm-snapshot: add more comments and other minor adjustments

cmd/swarm/swarm-snapshot/create.go

@@ -38,8 +38,9 @@ import (
 	cli "gopkg.in/urfave/cli.v1"
 )
 
-const noConnectionTimeout = 2 * time.Second
+const noConnectionTimeout = 1 * time.Second
 
+// create is used as the entry function for "create" app command.
 func create(ctx *cli.Context) error {
 	log.PrintOrigins(true)
 	log.Root().SetHandler(log.LvlFilterHandler(log.Lvl(ctx.Int("verbosity")), log.StreamHandler(os.Stdout, log.TerminalFormat(true))))
@@ -51,14 +52,16 @@ func create(ctx *cli.Context) error {
 	if err != nil {
 		return err
 	}
-	return createSnapshot(filename, ctx.Int("nodes"), ctx.String("services"))
+	return createSnapshot(filename, ctx.Int("nodes"), strings.Split(ctx.String("services"), ","))
 }
 
-func createSnapshot(filename string, nodes int, services string) (err error) {
+// createSnapshot creates a new snapshot on filesystem with provided filename,
+// number of nodes and service names.
+func createSnapshot(filename string, nodes int, services []string) (err error) {
 	log.Debug("create snapshot", "filename", filename, "nodes", nodes, "services", services)
 
 	sim := simulation.New(map[string]simulation.ServiceFunc{
-		bzzServiceName: func(ctx *adapters.ServiceContext, b *sync.Map) (node.Service, func(), error) {
+		"bzz": func(ctx *adapters.ServiceContext, b *sync.Map) (node.Service, func(), error) {
 			addr := network.NewAddr(ctx.Config.Node())
 			kad := network.NewKademlia(addr.Over(), network.NewKadParams())
 			hp := network.NewHiveParams()
@@ -80,6 +83,8 @@ func createSnapshot(filename string, nodes int, services string) (err error) {
 		return fmt.Errorf("add nodes: %v", err)
 	}
 
+	// wait for two some time to ensure no connections
+	// are established
 	events := make(chan *simulations.Event)
 	sub := sim.Net.Events().Subscribe(events)
 	select {
@@ -109,19 +114,21 @@ func createSnapshot(filename string, nodes int, services string) (err error) {
 
 	var snap *simulations.Snapshot
 	if len(services) > 0 {
-		addServices := strings.Split(services, ",")
+		// If service names are provided, include them in the snapshot.
+		// But, check if "bzz" service is not among them to remove it
+		// form the snapshot as it exists on snapshot creation.
 		var removeServices []string
-		var hasBzz bool
-		for _, s := range addServices {
-			if s == bzzServiceName {
-				hasBzz = true
+		var wantBzz bool
+		for _, s := range services {
+			if s == "bzz" {
+				wantBzz = true
 				break
 			}
 		}
-		if !hasBzz {
-			removeServices = append(removeServices, bzzServiceName)
+		if !wantBzz {
+			removeServices = []string{"bzz"}
 		}
-		snap, err = sim.Net.SnapshotWithServices(addServices, removeServices)
+		snap, err = sim.Net.SnapshotWithServices(services, removeServices)
 	} else {
 		snap, err = sim.Net.Snapshot()
 	}
@@ -135,6 +142,8 @@ func createSnapshot(filename string, nodes int, services string) (err error) {
 	return ioutil.WriteFile(filename, jsonsnapshot, 0666)
 }
 
+// touchPath creates an empty file and all subdirectories
+// that are missing.
 func touchPath(filename string) (string, error) {
 	if path.IsAbs(filename) {
 		if _, err := os.Stat(filename); err == nil {
@@ -164,6 +173,5 @@ func touchPath(filename string) (string, error) {
 		}
 	}
 
-	filename = filePath
-	return filename, nil
+	return filePath, nil
 }

cmd/swarm/swarm-snapshot/create_test.go

@@ -29,7 +29,9 @@ import (
 	"github.com/ethereum/go-ethereum/p2p/simulations"
 )
 
-//TestSnapshotCreate is a high level e2e test that tests for snapshot generation
+// TestSnapshotCreate is a high level e2e test that tests for snapshot generation.
+// It runs a few "create" commands with different flag values and loads generated
+// snapshot files to validate their content.
 func TestSnapshotCreate(t *testing.T) {
 	for _, v := range []struct {
 		name     string
@@ -48,8 +50,8 @@ func TestSnapshotCreate(t *testing.T) {
 			services: "stream,pss,zorglub",
 		},
 		{
-			name:     "services with " + bzzServiceName,
-			services: bzzServiceName + ",pss",
+			name:     "services with bzz",
+			services: "bzz,pss",
 		},
 	} {
 		t.Run(v.name, func(t *testing.T) {
@@ -75,8 +77,8 @@ func TestSnapshotCreate(t *testing.T) {
 			testCmd := runSnapshot(t, append(args, file.Name())...)
 
 			testCmd.ExpectExit()
-			if testCmd.ExitStatus() != 0 {
-				t.Fatal("expected exit code 0")
+			if code := testCmd.ExitStatus(); code != 0 {
+				t.Fatalf("command exit code %v, expected 0", code)
 			}
 
 			f, err := os.Open(file.Name())
@@ -117,8 +119,10 @@ func TestSnapshotCreate(t *testing.T) {
 			if v.services != "" {
 				wantServices = strings.Split(v.services, ",")
 			} else {
-				wantServices = []string{bzzServiceName}
+				wantServices = []string{"bzz"}
 			}
+			// sort service names so they can be comparable
+			// as strings to every node sorted services
 			sort.Strings(wantServices)
 
 			for i, n := range snap.Nodes {

cmd/swarm/swarm-snapshot/main.go

@@ -26,10 +26,8 @@ import (
 
 var gitCommit string // Git SHA1 commit hash of the release (set via linker flags)
 
-const (
-	defaultNodes   = 10
-	bzzServiceName = "bzz"
-)
+// default value for "create" command --nodes flag
+const defaultNodes = 10
 
 func main() {
 	err := newApp().Run(os.Args)
@@ -39,12 +37,15 @@ func main() {
 	}
 }
 
+// newApp construct a new instance of Swarm Snapshot Utility.
+// Method Run is called on it in the main function and in tests.
 func newApp() (app *cli.App) {
 	app = utils.NewApp(gitCommit, "Swarm Snapshot Utility")
 
 	app.Name = "swarm-snapshot"
 	app.Usage = ""
 
+	// app flags (for all commands)
 	app.Flags = []cli.Flag{
 		cli.IntFlag{
 			Name:  "verbosity",
@@ -59,6 +60,9 @@ func newApp() (app *cli.App) {
 			Aliases: []string{"c"},
 			Usage:   "create a swarm snapshot",
 			Action:  create,
+			// Flags only for "create" command.
+			// Allow app flags to be specified after the
+			// command argument.
 			Flags: append(app.Flags,
 				cli.IntFlag{
 					Name:  "nodes",
@@ -67,7 +71,7 @@ func newApp() (app *cli.App) {
 				},
 				cli.StringFlag{
 					Name:  "services",
-					Value: bzzServiceName,
+					Value: "bzz",
 					Usage: "comma separated list of services to boot the nodes with",
 				},
 			),
@@ -77,6 +81,8 @@ func newApp() (app *cli.App) {
 			Aliases: []string{"v"},
 			Usage:   "verify a swarm snapshot",
 			Action:  verify,
+			// Allow app flags to be specified after the
+			// command argument.
 			Flags: app.Flags,
 		},
 	}

cmd/swarm/swarm-snapshot/verify.go

@@ -32,6 +32,7 @@ import (
 	cli "gopkg.in/urfave/cli.v1"
 )
 
+// verify is used as the entry function for "verify" app command.
 func verify(ctx *cli.Context) error {
 	log.PrintOrigins(true)
 	log.Root().SetHandler(log.LvlFilterHandler(log.Lvl(ctx.Int("verbosity")), log.StreamHandler(os.Stdout, log.TerminalFormat(true))))
@@ -42,9 +43,11 @@ func verify(ctx *cli.Context) error {
 	return verifySnapshot(ctx.Args()[0])
 }
 
+// verifySnapshot constructs a simulation, uploads a snapshot from
+// a file with provided filename and validates that kademlia is healthy.
 func verifySnapshot(filename string) (err error) {
 	sim := simulation.New(map[string]simulation.ServiceFunc{
-		bzzServiceName: func(ctx *adapters.ServiceContext, b *sync.Map) (node.Service, func(), error) {
+		"bzz": func(ctx *adapters.ServiceContext, b *sync.Map) (node.Service, func(), error) {
 			addr := network.NewAddr(ctx.Config.Node())
 			kad := network.NewKademlia(addr.Over(), network.NewKadParams())
 			hp := network.NewHiveParams()

cmd/swarm/swarm-snapshot/verify_test.go

@@ -20,6 +20,8 @@ import (
 	"testing"
 )
 
+// TestSnapshotVerify executes "verify" command with a
+// pregenerated snapshot file that is valid.
 func TestSnapshotVerify(t *testing.T) {
 	snap := runSnapshot(t,
 		"verify",
@@ -27,7 +29,7 @@ func TestSnapshotVerify(t *testing.T) {
 	)
 
 	snap.ExpectExit()
-	if snap.ExitStatus() != 0 {
-		t.Fatal("expected exit code 0")
+	if code := snap.ExitStatus(); code != 0 {
+		t.Fatalf("command exit code %v, expected 0", code)
 	}
 }