Simplify gateway backend registration (#5111)

cmd/gateway-azure.go

@@ -33,13 +33,86 @@ import (
 
 	"github.com/Azure/azure-sdk-for-go/storage"
 	humanize "github.com/dustin/go-humanize"
+	"github.com/minio/cli"
 	"github.com/minio/minio-go/pkg/policy"
 	"github.com/minio/minio/pkg/hash"
 )
 
-const globalAzureAPIVersion = "2016-05-31"
+const (
-const azureBlockSize = 100 * humanize.MiByte
+	globalAzureAPIVersion      = "2016-05-31"
-const metadataObjectNameTemplate = globalMinioSysTmp + "multipart/v1/%s.%x/azure.json"
+	azureBlockSize             = 100 * humanize.MiByte
+	metadataObjectNameTemplate = globalMinioSysTmp + "multipart/v1/%s.%x/azure.json"
+	azureBackend               = "azure"
+)
+
+func init() {
+	const azureGatewayTemplate = `NAME:
+  {{.HelpName}} - {{.Usage}}
+
+USAGE:
+  {{.HelpName}} {{if .VisibleFlags}}[FLAGS]{{end}} [ENDPOINT]
+{{if .VisibleFlags}}
+FLAGS:
+  {{range .VisibleFlags}}{{.}}
+  {{end}}{{end}}
+ENDPOINT:
+  Azure server endpoint. Default ENDPOINT is https://core.windows.net
+
+ENVIRONMENT VARIABLES:
+  ACCESS:
+     MINIO_ACCESS_KEY: Username or access key of Azure storage.
+     MINIO_SECRET_KEY: Password or secret key of Azure storage.
+
+  BROWSER:
+     MINIO_BROWSER: To disable web browser access, set this value to "off".
+
+EXAMPLES:
+  1. Start minio gateway server for Azure Blob Storage backend.
+      $ export MINIO_ACCESS_KEY=azureaccountname
+      $ export MINIO_SECRET_KEY=azureaccountkey
+      $ {{.HelpName}}
+
+  2. Start minio gateway server for Azure Blob Storage backend on custom endpoint.
+      $ export MINIO_ACCESS_KEY=azureaccountname
+      $ export MINIO_SECRET_KEY=azureaccountkey
+      $ {{.HelpName}} https://azure.example.com
+
+`
+
+	MustRegisterGatewayCommand(cli.Command{
+		Name:               azureBackend,
+		Usage:              "Microsoft Azure Blob Storage.",
+		Action:             azureGatewayMain,
+		CustomHelpTemplate: azureGatewayTemplate,
+		Flags:              append(serverFlags, globalFlags...),
+		HideHelpCommand:    true,
+	})
+}
+
+// Handler for 'minio gateway azure' command line.
+func azureGatewayMain(ctx *cli.Context) {
+	// Validate gateway arguments.
+	host := ctx.Args().First()
+	// Validate gateway arguments.
+	fatalIf(validateGatewayArguments(ctx.GlobalString("address"), host), "Invalid argument")
+
+	startGateway(ctx, &AzureGateway{host})
+}
+
+// AzureGateway implements Gateway.
+type AzureGateway struct {
+	host string
+}
+
+// Name implements Gateway interface.
+func (g *AzureGateway) Name() string {
+	return azureBackend
+}
+
+// NewGatewayLayer initializes azure blob storage client and returns AzureObjects.
+func (g *AzureGateway) NewGatewayLayer() (GatewayLayer, error) {
+	return newAzureLayer(g.host)
+}
 
 // s3MetaToAzureProperties converts metadata meant for S3 PUT/COPY
 // object into Azure data structures - BlobMetadata and

cmd/gateway-b2.go

@@ -29,6 +29,7 @@ import (
 	"time"
 
 	b2 "github.com/minio/blazer/base"
+	"github.com/minio/cli"
 	"github.com/minio/minio-go/pkg/policy"
 	h2 "github.com/minio/minio/pkg/hash"
 )
@@ -37,8 +38,65 @@ import (
 const (
 	bucketTypePrivate  = "allPrivate"
 	bucketTypeReadOnly = "allPublic"
+	b2Backend          = "b2"
 )
 
+func init() {
+	const b2GatewayTemplate = `NAME:
+  {{.HelpName}} - {{.Usage}}
+
+USAGE:
+  {{.HelpName}} {{if .VisibleFlags}}[FLAGS]{{end}}
+{{if .VisibleFlags}}
+FLAGS:
+  {{range .VisibleFlags}}{{.}}
+  {{end}}{{end}}
+ENVIRONMENT VARIABLES:
+  ACCESS:
+     MINIO_ACCESS_KEY: B2 account id.
+     MINIO_SECRET_KEY: B2 application key.
+
+  BROWSER:
+     MINIO_BROWSER: To disable web browser access, set this value to "off".
+
+EXAMPLES:
+  1. Start minio gateway server for B2 backend.
+      $ export MINIO_ACCESS_KEY=accountID
+      $ export MINIO_SECRET_KEY=applicationKey
+      $ {{.HelpName}}
+
+`
+
+	MustRegisterGatewayCommand(cli.Command{
+		Name:               b2Backend,
+		Usage:              "Backblaze B2.",
+		Action:             b2GatewayMain,
+		CustomHelpTemplate: b2GatewayTemplate,
+		Flags:              append(serverFlags, globalFlags...),
+		HideHelpCommand:    true,
+	})
+}
+
+// Handler for 'minio gateway b2' command line.
+func b2GatewayMain(ctx *cli.Context) {
+	startGateway(ctx, &B2Gateway{})
+}
+
+// B2Gateway implements Gateway.
+type B2Gateway struct{}
+
+// Name implements Gateway interface.
+func (g *B2Gateway) Name() string {
+	return b2Backend
+}
+
+// NewGatewayLayer returns b2 gateway layer, implements GatewayLayer interface to
+// talk to B2 remote backend.
+func (g *B2Gateway) NewGatewayLayer() (GatewayLayer, error) {
+	log.Println(colorYellow("\n               *** Warning: Not Ready for Production ***"))
+	return newB2GatewayLayer()
+}
+
 // b2Object implements gateway for Minio and BackBlaze B2 compatible object storage servers.
 type b2Objects struct {
 	gatewayUnsupported
@@ -49,9 +107,8 @@ type b2Objects struct {
 	ctx        context.Context
 }
 
-// newB2Gateway returns b2 gateway layer, implements GatewayLayer interface to
+// newB2GatewayLayer returns b2 gateway layer.
-// talk to B2 remote backend.
+func newB2GatewayLayer() (GatewayLayer, error) {
-func newB2Gateway() (GatewayLayer, error) {
 	ctx := context.Background()
 	creds := serverConfig.GetCredential()
 

cmd/gateway-gcs.go

@@ -30,16 +30,15 @@ import (
 	"strings"
 	"time"
 
-	"golang.org/x/oauth2/google"
-
 	"cloud.google.com/go/storage"
-	cloudresourcemanager "google.golang.org/api/cloudresourcemanager/v1"
+	"github.com/minio/cli"
-	"google.golang.org/api/googleapi"
-	"google.golang.org/api/iterator"
-
 	minio "github.com/minio/minio-go"
 	"github.com/minio/minio-go/pkg/policy"
 	"github.com/minio/minio/pkg/hash"
+	"golang.org/x/oauth2/google"
+	cloudresourcemanager "google.golang.org/api/cloudresourcemanager/v1"
+	"google.golang.org/api/googleapi"
+	"google.golang.org/api/iterator"
 )
 
 var (
@@ -78,8 +77,85 @@ const (
 
 	// Project ID key in credentials.json
 	gcsProjectIDKey = "project_id"
+
+	gcsBackend = "gcs"
 )
 
+func init() {
+	const gcsGatewayTemplate = `NAME:
+  {{.HelpName}} - {{.Usage}}
+
+USAGE:
+  {{.HelpName}} {{if .VisibleFlags}}[FLAGS]{{end}} [PROJECTID]
+{{if .VisibleFlags}}
+FLAGS:
+  {{range .VisibleFlags}}{{.}}
+  {{end}}{{end}}
+PROJECTID:
+  GCS project-id should be provided if GOOGLE_APPLICATION_CREDENTIALS environmental variable is not set.
+
+ENVIRONMENT VARIABLES:
+  ACCESS:
+     MINIO_ACCESS_KEY: Username or access key of GCS.
+     MINIO_SECRET_KEY: Password or secret key of GCS.
+
+  BROWSER:
+     MINIO_BROWSER: To disable web browser access, set this value to "off".
+
+  GCS credentials file:
+     GOOGLE_APPLICATION_CREDENTIALS: Path to credentials.json
+
+EXAMPLES:
+  1. Start minio gateway server for GCS backend.
+      $ export GOOGLE_APPLICATION_CREDENTIALS=/path/to/credentials.json
+      (Instructions to generate credentials : https://developers.google.com/identity/protocols/application-default-credentials)
+      $ export MINIO_ACCESS_KEY=accesskey
+      $ export MINIO_SECRET_KEY=secretkey
+      $ {{.HelpName}} mygcsprojectid
+
+`
+
+	MustRegisterGatewayCommand(cli.Command{
+		Name:               gcsBackend,
+		Usage:              "Google Cloud Storage.",
+		Action:             gcsGatewayMain,
+		CustomHelpTemplate: gcsGatewayTemplate,
+		Flags:              append(serverFlags, globalFlags...),
+		HideHelpCommand:    true,
+	})
+}
+
+// Handler for 'minio gateway gcs' command line.
+func gcsGatewayMain(ctx *cli.Context) {
+	projectID := ctx.Args().First()
+	if projectID == "" && os.Getenv("GOOGLE_APPLICATION_CREDENTIALS") == "" {
+		errorIf(errGCSProjectIDNotFound, "project-id should be provided as argument or GOOGLE_APPLICATION_CREDENTIALS should be set with path to credentials.json")
+		cli.ShowCommandHelpAndExit(ctx, "gcs", 1)
+	}
+	if projectID != "" && !isValidGCSProjectIDFormat(projectID) {
+		errorIf(errGCSInvalidProjectID, "Unable to start GCS gateway with %s", ctx.Args().First())
+		cli.ShowCommandHelpAndExit(ctx, "gcs", 1)
+	}
+
+	startGateway(ctx, &GCSGateway{projectID})
+}
+
+// GCSGateway implements Gateway.
+type GCSGateway struct {
+	projectID string
+}
+
+// Name returns the name of gcs gatewaylayer.
+func (g *GCSGateway) Name() string {
+	return gcsBackend
+}
+
+// NewGatewayLayer returns gcs gatewaylayer.
+func (g *GCSGateway) NewGatewayLayer() (GatewayLayer, error) {
+	log.Println(colorYellow("\n               *** Warning: Not Ready for Production ***"))
+	return newGCSGatewayLayer(g.projectID)
+}
+
 // Stored in gcs.json - Contents of this file is not used anywhere. It can be
 // used for debugging purposes.
 type gcsMultipartMetaV1 struct {
@@ -275,8 +351,8 @@ func gcsParseProjectID(credsFile string) (projectID string, err error) {
 	return googleCreds[gcsProjectIDKey], err
 }
 
-// newGCSGateway returns gcs gatewaylayer
+// newGCSGatewayLayer returns gcs gatewaylayer
-func newGCSGateway(projectID string) (GatewayLayer, error) {
+func newGCSGatewayLayer(projectID string) (GatewayLayer, error) {
 	ctx := context.Background()
 
 	var err error

cmd/gateway-main.go

@@ -31,212 +31,41 @@ import (
 	miniohttp "github.com/minio/minio/pkg/http"
 )
 
-const azureGatewayTemplate = `NAME:
-  {{.HelpName}} - {{.Usage}}
-
-USAGE:
-  {{.HelpName}} {{if .VisibleFlags}}[FLAGS]{{end}} [ENDPOINT]
-{{if .VisibleFlags}}
-FLAGS:
-  {{range .VisibleFlags}}{{.}}
-  {{end}}{{end}}
-ENDPOINT:
-  Azure server endpoint. Default ENDPOINT is https://core.windows.net
-
-ENVIRONMENT VARIABLES:
-  ACCESS:
-     MINIO_ACCESS_KEY: Username or access key of Azure storage.
-     MINIO_SECRET_KEY: Password or secret key of Azure storage.
-
-  BROWSER:
-     MINIO_BROWSER: To disable web browser access, set this value to "off".
-
-EXAMPLES:
-  1. Start minio gateway server for Azure Blob Storage backend.
-      $ export MINIO_ACCESS_KEY=azureaccountname
-      $ export MINIO_SECRET_KEY=azureaccountkey
-      $ {{.HelpName}}
-
-  2. Start minio gateway server for Azure Blob Storage backend on custom endpoint.
-      $ export MINIO_ACCESS_KEY=azureaccountname
-      $ export MINIO_SECRET_KEY=azureaccountkey
-      $ {{.HelpName}} https://azure.example.com
-`
-
-const s3GatewayTemplate = `NAME:
-  {{.HelpName}} - {{.Usage}}
-
-USAGE:
-  {{.HelpName}} {{if .VisibleFlags}}[FLAGS]{{end}} [ENDPOINT]
-{{if .VisibleFlags}}
-FLAGS:
-  {{range .VisibleFlags}}{{.}}
-  {{end}}{{end}}
-ENDPOINT:
-  S3 server endpoint. Default ENDPOINT is https://s3.amazonaws.com
-
-ENVIRONMENT VARIABLES:
-  ACCESS:
-     MINIO_ACCESS_KEY: Username or access key of S3 storage.
-     MINIO_SECRET_KEY: Password or secret key of S3 storage.
-
-  BROWSER:
-     MINIO_BROWSER: To disable web browser access, set this value to "off".
-
-EXAMPLES:
-  1. Start minio gateway server for AWS S3 backend.
-      $ export MINIO_ACCESS_KEY=accesskey
-      $ export MINIO_SECRET_KEY=secretkey
-      $ {{.HelpName}}
-
-  2. Start minio gateway server for S3 backend on custom endpoint.
-      $ export MINIO_ACCESS_KEY=Q3AM3UQ867SPQQA43P2F
-      $ export MINIO_SECRET_KEY=zuf+tfteSlswRu7BJ86wekitnifILbZam1KYY3TG
-      $ {{.HelpName}} https://play.minio.io:9000
-`
-
-const gcsGatewayTemplate = `NAME:
-  {{.HelpName}} - {{.Usage}}
-
-USAGE:
-  {{.HelpName}} {{if .VisibleFlags}}[FLAGS]{{end}} [PROJECTID]
-{{if .VisibleFlags}}
-FLAGS:
-  {{range .VisibleFlags}}{{.}}
-  {{end}}{{end}}
-PROJECTID:
-  GCS project-id should be provided if GOOGLE_APPLICATION_CREDENTIALS environmental variable is not set.
-
-ENVIRONMENT VARIABLES:
-  ACCESS:
-     MINIO_ACCESS_KEY: Username or access key of GCS.
-     MINIO_SECRET_KEY: Password or secret key of GCS.
-
-  BROWSER:
-     MINIO_BROWSER: To disable web browser access, set this value to "off".
-
-  GCS credentials file:
-     GOOGLE_APPLICATION_CREDENTIALS: Path to credentials.json
-
-EXAMPLES:
-  1. Start minio gateway server for GCS backend.
-      $ export GOOGLE_APPLICATION_CREDENTIALS=/path/to/credentials.json
-      (Instructions to generate credentials : https://developers.google.com/identity/protocols/application-default-credentials)
-      $ export MINIO_ACCESS_KEY=accesskey
-      $ export MINIO_SECRET_KEY=secretkey
-      $ {{.HelpName}} mygcsprojectid
-
-`
-
-const b2GatewayTemplate = `NAME:
-  {{.HelpName}} - {{.Usage}}
-
-USAGE:
-  {{.HelpName}} {{if .VisibleFlags}}[FLAGS]{{end}}
-{{if .VisibleFlags}}
-FLAGS:
-  {{range .VisibleFlags}}{{.}}
-  {{end}}{{end}}
-ENVIRONMENT VARIABLES:
-  ACCESS:
-     MINIO_ACCESS_KEY: B2 account id.
-     MINIO_SECRET_KEY: B2 application key.
-
-  BROWSER:
-     MINIO_BROWSER: To disable web browser access, set this value to "off".
-
-EXAMPLES:
-  1. Start minio gateway server for B2 backend.
-      $ export MINIO_ACCESS_KEY=accountID
-      $ export MINIO_SECRET_KEY=applicationKey
-      $ {{.HelpName}}
-
-`
-
 var (
-	azureBackendCmd = cli.Command{
-		Name:               "azure",
-		Usage:              "Microsoft Azure Blob Storage.",
-		Action:             azureGatewayMain,
-		CustomHelpTemplate: azureGatewayTemplate,
-		Flags:              append(serverFlags, globalFlags...),
-		HideHelpCommand:    true,
-	}
-
-	s3BackendCmd = cli.Command{
-		Name:               "s3",
-		Usage:              "Amazon Simple Storage Service (S3).",
-		Action:             s3GatewayMain,
-		CustomHelpTemplate: s3GatewayTemplate,
-		Flags:              append(serverFlags, globalFlags...),
-		HideHelpCommand:    true,
-	}
-
-	gcsBackendCmd = cli.Command{
-		Name:               "gcs",
-		Usage:              "Google Cloud Storage.",
-		Action:             gcsGatewayMain,
-		CustomHelpTemplate: gcsGatewayTemplate,
-		Flags:              append(serverFlags, globalFlags...),
-		HideHelpCommand:    true,
-	}
-
-	b2BackendCmd = cli.Command{
-		Name:               "b2",
-		Usage:              "Backblaze B2.",
-		Action:             b2GatewayMain,
-		CustomHelpTemplate: b2GatewayTemplate,
-		Flags:              append(serverFlags, globalFlags...),
-		HideHelpCommand:    true,
-	}
-
 	gatewayCmd = cli.Command{
 		Name:            "gateway",
 		Usage:           "Start object storage gateway.",
 		Flags:           append(serverFlags, globalFlags...),
 		HideHelpCommand: true,
-		Subcommands:     []cli.Command{azureBackendCmd, s3BackendCmd, gcsBackendCmd, b2BackendCmd},
 	}
 )
 
-// Represents the type of the gateway backend.
+// Gateway represents a gateway backend.
-type gatewayBackend string
+type Gateway interface {
-
+	// Name returns the unique name of the gateway.
-const (
+	Name() string
-	azureBackend gatewayBackend = "azure"
+	// NewGatewayLayer returns a new gateway layer.
-	s3Backend    gatewayBackend = "s3"
+	NewGatewayLayer() (GatewayLayer, error)
-	gcsBackend   gatewayBackend = "gcs"
-	b2Backend    gatewayBackend = "b2"
-	// Add more backends here.
-)
-
-// Initialize gateway layer depending on the backend type.
-// Supported backend types are
-//
-// - Azure Blob Storage.
-// - AWS S3.
-// - Google Cloud Storage.
-// - Backblaze B2.
-// - Add your favorite backend here.
-func newGatewayLayer(backendType gatewayBackend, arg string) (GatewayLayer, error) {
-	switch backendType {
-	case azureBackend:
-		return newAzureLayer(arg)
-	case s3Backend:
-		return newS3Gateway(arg)
-	case gcsBackend:
-		// FIXME: The following print command is temporary and
-		// will be removed when gcs is ready for production use.
-		log.Println(colorYellow("\n               *** Warning: Not Ready for Production ***"))
-		return newGCSGateway(arg)
-	case b2Backend:
-		// FIXME: The following print command is temporary and
-		// will be removed when B2 is ready for production use.
-		log.Println(colorYellow("\n               *** Warning: Not Ready for Production ***"))
-		return newB2Gateway()
 }
 
-	return nil, fmt.Errorf("Unrecognized backend type %s", backendType)
+// RegisterGatewayCommand registers a new command for gateway.
+func RegisterGatewayCommand(cmd cli.Command) error {
+	// We should not have multiple subcommands with same name.
+	for _, c := range gatewayCmd.Subcommands {
+		if c.Name == cmd.Name {
+			return fmt.Errorf("duplicate gateway: %s", cmd.Name)
+		}
+	}
+
+	gatewayCmd.Subcommands = append(gatewayCmd.Subcommands, cmd)
+	return nil
+}
+
+// MustRegisterGatewayCommand is like RegisterGatewayCommand but panics instead of returning error.
+func MustRegisterGatewayCommand(cmd cli.Command) {
+	if err := RegisterGatewayCommand(cmd); err != nil {
+		panic(err)
+	}
 }
 
 // Return endpoint.
@@ -292,62 +121,8 @@ func validateGatewayArguments(serverAddr, endpointAddr string) error {
 	return nil
 }
 
-// Handler for 'minio gateway azure' command line.
+// Handler for 'minio gateway <name>'.
-func azureGatewayMain(ctx *cli.Context) {
+func startGateway(ctx *cli.Context, gw Gateway) {
-	if ctx.Args().Present() && ctx.Args().First() == "help" {
-		cli.ShowCommandHelpAndExit(ctx, "azure", 1)
-	}
-
-	// Validate gateway arguments.
-	fatalIf(validateGatewayArguments(ctx.GlobalString("address"), ctx.Args().First()), "Invalid argument")
-
-	gatewayMain(ctx, azureBackend)
-}
-
-// Handler for 'minio gateway s3' command line.
-func s3GatewayMain(ctx *cli.Context) {
-	if ctx.Args().Present() && ctx.Args().First() == "help" {
-		cli.ShowCommandHelpAndExit(ctx, "s3", 1)
-	}
-
-	// Validate gateway arguments.
-	fatalIf(validateGatewayArguments(ctx.GlobalString("address"), ctx.Args().First()), "Invalid argument")
-
-	gatewayMain(ctx, s3Backend)
-}
-
-// Handler for 'minio gateway gcs' command line
-func gcsGatewayMain(ctx *cli.Context) {
-	if ctx.Args().Present() && ctx.Args().First() == "help" {
-		cli.ShowCommandHelpAndExit(ctx, "gcs", 1)
-	}
-
-	projectID := ctx.Args().First()
-	if projectID == "" && os.Getenv("GOOGLE_APPLICATION_CREDENTIALS") == "" {
-		errorIf(errGCSProjectIDNotFound, "project-id should be provided as argument or GOOGLE_APPLICATION_CREDENTIALS should be set with path to credentials.json")
-		cli.ShowCommandHelpAndExit(ctx, "gcs", 1)
-	}
-	if projectID != "" && !isValidGCSProjectIDFormat(projectID) {
-		errorIf(errGCSInvalidProjectID, "Unable to start GCS gateway with %s", ctx.Args().First())
-		cli.ShowCommandHelpAndExit(ctx, "gcs", 1)
-	}
-
-	gatewayMain(ctx, gcsBackend)
-}
-
-func b2GatewayMain(ctx *cli.Context) {
-	if ctx.Args().Present() && ctx.Args().First() == "help" {
-		cli.ShowCommandHelpAndExit(ctx, "b2", 1)
-	}
-
-	// Validate gateway arguments.
-	fatalIf(validateGatewayArguments(ctx.GlobalString("address"), ctx.Args().First()), "Invalid argument")
-
-	gatewayMain(ctx, b2Backend)
-}
-
-// Handler for 'minio gateway'.
-func gatewayMain(ctx *cli.Context, backendType gatewayBackend) {
 	// Get quiet flag from command line argument.
 	quietFlag := ctx.Bool("quiet") || ctx.GlobalBool("quiet")
 	if quietFlag {
@@ -367,8 +142,9 @@ func gatewayMain(ctx *cli.Context, backendType gatewayBackend) {
 	handleCommonEnvVars()
 
 	// Validate if we have access, secret set through environment.
+	gatewayName := gw.Name()
 	if !globalIsEnvCreds {
-		fatalIf(fmt.Errorf("Access and Secret keys should be set through ENVs for backend [%s]", backendType), "")
+		fatalIf(fmt.Errorf("Access and Secret keys should be set through ENVs for backend [%s]", gatewayName), "")
 	}
 
 	// Create certs path.
@@ -390,7 +166,11 @@ func gatewayMain(ctx *cli.Context, backendType gatewayBackend) {
 
 	initNSLock(false) // Enable local namespace lock.
 
-	newObject, err := newGatewayLayer(backendType, ctx.Args().First())
+	if ctx.Args().First() == "help" {
+		cli.ShowCommandHelpAndExit(ctx, gatewayName, 1)
+	}
+
+	newObject, err := gw.NewGatewayLayer()
 	fatalIf(err, "Unable to initialize gateway layer")
 
 	router := mux.NewRouter().SkipClean(true)
@@ -445,23 +225,12 @@ func gatewayMain(ctx *cli.Context, backendType gatewayBackend) {
 
 	// Prints the formatted startup message once object layer is initialized.
 	if !quietFlag {
-		mode := ""
+		mode := globalMinioModeGatewayPrefix + gatewayName
-		switch gatewayBackend(backendType) {
-		case azureBackend:
-			mode = globalMinioModeGatewayAzure
-		case gcsBackend:
-			mode = globalMinioModeGatewayGCS
-		case s3Backend:
-			mode = globalMinioModeGatewayS3
-		case b2Backend:
-			mode = globalMinioModeGatewayB2
-		}
-
 		// Check update mode.
 		checkUpdate(mode)
 
 		// Print gateway startup message.
-		printGatewayStartupMessage(getAPIEndpoints(gatewayAddr), backendType)
+		printGatewayStartupMessage(getAPIEndpoints(gatewayAddr), gatewayName)
 	}
 
 	handleSignals()

cmd/gateway-main_test.go

@@ -19,8 +19,31 @@ package cmd
 import (
 	"strings"
 	"testing"
+
+	"github.com/minio/cli"
 )
 
+// Test RegisterGatewayCommand
+func TestRegisterGatewayCommand(t *testing.T) {
+	var err error
+
+	cmd := cli.Command{Name: "test"}
+	err = RegisterGatewayCommand(cmd)
+	if err != nil {
+		t.Errorf("RegisterGatewayCommand got unexpected error: %s", err)
+	}
+
+	// Should returns 'duplicated' error
+	err = RegisterGatewayCommand(cmd)
+	if err == nil {
+		t.Errorf("RegisterGatewayCommand twice with same name should return error")
+	} else {
+		if err.Error() != "duplicate gateway: test" {
+			t.Errorf("RegisterGatewayCommand got unexpected error: %s", err)
+		}
+	}
+}
+
 // Test parseGatewayEndpoint
 func TestParseGatewayEndpoint(t *testing.T) {
 	testCases := []struct {

cmd/gateway-s3.go

@@ -20,12 +20,85 @@ import (
 	"io"
 	"net/http"
 
+	"github.com/minio/cli"
 	minio "github.com/minio/minio-go"
 	"github.com/minio/minio-go/pkg/policy"
 	"github.com/minio/minio-go/pkg/s3utils"
 	"github.com/minio/minio/pkg/hash"
 )
 
+const (
+	s3Backend = "s3"
+)
+
+func init() {
+	const s3GatewayTemplate = `NAME:
+  {{.HelpName}} - {{.Usage}}
+
+USAGE:
+  {{.HelpName}} {{if .VisibleFlags}}[FLAGS]{{end}} [ENDPOINT]
+{{if .VisibleFlags}}
+FLAGS:
+  {{range .VisibleFlags}}{{.}}
+  {{end}}{{end}}
+ENDPOINT:
+  S3 server endpoint. Default ENDPOINT is https://s3.amazonaws.com
+
+ENVIRONMENT VARIABLES:
+  ACCESS:
+     MINIO_ACCESS_KEY: Username or access key of S3 storage.
+     MINIO_SECRET_KEY: Password or secret key of S3 storage.
+
+  BROWSER:
+     MINIO_BROWSER: To disable web browser access, set this value to "off".
+
+EXAMPLES:
+  1. Start minio gateway server for AWS S3 backend.
+      $ export MINIO_ACCESS_KEY=accesskey
+      $ export MINIO_SECRET_KEY=secretkey
+      $ {{.HelpName}}
+
+  2. Start minio gateway server for S3 backend on custom endpoint.
+      $ export MINIO_ACCESS_KEY=Q3AM3UQ867SPQQA43P2F
+      $ export MINIO_SECRET_KEY=zuf+tfteSlswRu7BJ86wekitnifILbZam1KYY3TG
+      $ {{.HelpName}} https://play.minio.io:9000
+`
+
+	MustRegisterGatewayCommand(cli.Command{
+		Name:               s3Backend,
+		Usage:              "Amazon Simple Storage Service (S3).",
+		Action:             s3GatewayMain,
+		CustomHelpTemplate: s3GatewayTemplate,
+		Flags:              append(serverFlags, globalFlags...),
+		HideHelpCommand:    true,
+	})
+}
+
+// Handler for 'minio gateway s3' command line.
+func s3GatewayMain(ctx *cli.Context) {
+	// Validate gateway arguments.
+	host := ctx.Args().First()
+	// Validate gateway arguments.
+	fatalIf(validateGatewayArguments(ctx.GlobalString("address"), host), "Invalid argument")
+
+	startGateway(ctx, &S3Gateway{host})
+}
+
+// S3Gateway implements Gateway.
+type S3Gateway struct {
+	host string
+}
+
+// Name implements Gateway interface.
+func (g *S3Gateway) Name() string {
+	return s3Backend
+}
+
+// NewGatewayLayer returns s3 gatewaylayer.
+func (g *S3Gateway) NewGatewayLayer() (GatewayLayer, error) {
+	return newS3GatewayLayer(g.host)
+}
+
 // s3ToObjectError converts Minio errors to minio object layer errors.
 func s3ToObjectError(err error, params ...string) error {
 	if err == nil {
@@ -101,8 +174,8 @@ type s3Objects struct {
 	anonClient *minio.Core
 }
 
-// newS3Gateway returns s3 gatewaylayer
+// newS3GatewayLayer returns s3 gatewaylayer
-func newS3Gateway(host string) (GatewayLayer, error) {
+func newS3GatewayLayer(host string) (GatewayLayer, error) {
 	var err error
 	var endpoint string
 	var secure = true

cmd/gateway-startup-msg.go

@@ -22,7 +22,7 @@ import (
 )
 
 // Prints the formatted startup message.
-func printGatewayStartupMessage(apiEndPoints []string, backendType gatewayBackend) {
+func printGatewayStartupMessage(apiEndPoints []string, backendType string) {
 	strippedAPIEndpoints := stripStandardPorts(apiEndPoints)
 
 	// Prints credential.

cmd/globals.go

@@ -50,10 +50,7 @@ const (
 	globalMinioModeFS              = "mode-server-fs"
 	globalMinioModeXL              = "mode-server-xl"
 	globalMinioModeDistXL          = "mode-server-distributed-xl"
-	globalMinioModeGatewayAzure    = "mode-gateway-azure"
+	globalMinioModeGatewayPrefix   = "mode-gateway-"
-	globalMinioModeGatewayS3       = "mode-gateway-s3"
-	globalMinioModeGatewayGCS      = "mode-gateway-gcs"
-	globalMinioModeGatewayB2       = "mode-gateway-b2"
 
 	// globalMinioSysTmp prefix is used in Azure/GCS gateway for save metadata sent by Initialize Multipart Upload API.
 	globalMinioSysTmp = "minio.sys.tmp/"

cmd/web-handlers.go

@@ -728,20 +728,10 @@ func readBucketAccessPolicy(objAPI ObjectLayer, bucketName string) (policy.Bucke
 
 func getBucketAccessPolicy(objAPI ObjectLayer, bucketName string) (policy.BucketAccessPolicy, error) {
 	// FIXME: remove this code when S3 layer for gateway and server is unified.
-	var policyInfo policy.BucketAccessPolicy
+	if layer, ok := objAPI.(GatewayLayer); ok {
-	var err error
+		return layer.GetBucketPolicies(bucketName)
-
-	switch layer := objAPI.(type) {
-	case *s3Objects:
-		policyInfo, err = layer.GetBucketPolicies(bucketName)
-	case *azureObjects:
-		policyInfo, err = layer.GetBucketPolicies(bucketName)
-	case *gcsGateway:
-		policyInfo, err = layer.GetBucketPolicies(bucketName)
-	default:
-		policyInfo, err = readBucketAccessPolicy(objAPI, bucketName)
 	}
-	return policyInfo, err
+	return readBucketAccessPolicy(objAPI, bucketName)
 }
 
 // GetBucketPolicy - get bucket policy for the requested prefix.