centralize harded-code message

Signed-off-by: Fahed Dorgaa <fahed.dorgaa@gmail.com>

client.go

@@ -137,7 +137,7 @@ func New(address string, opts ...ClientOpt) (*Client, error) {
 		c.conn, c.connector = conn, connector
 	}
 	if copts.services == nil && c.conn == nil {
-		return nil, errors.New("no grpc connection or services is available")
+		return nil, errdefs.ErrNoGRPCAndService
 	}
 
 	// check namespace labels for default runtime
@@ -196,7 +196,7 @@ type Client struct {
 // Reconnect re-establishes the GRPC connection to the containerd daemon
 func (c *Client) Reconnect() error {
 	if c.connector == nil {
-		return errors.New("unable to reconnect to containerd, no connector available")
+		return errdefs.ErrReconnectFailed
 	}
 	c.connMu.Lock()
 	defer c.connMu.Unlock()
@@ -219,7 +219,7 @@ func (c *Client) IsServing(ctx context.Context) (bool, error) {
 	c.connMu.Lock()
 	if c.conn == nil {
 		c.connMu.Unlock()
-		return false, errors.New("no grpc connection available")
+		return false, errdefs.ErrNoGRPC
 	}
 	c.connMu.Unlock()
 	r, err := c.HealthService().Check(ctx, &grpc_health_v1.HealthCheckRequest{}, grpc.WaitForReady(true))
@@ -350,7 +350,7 @@ func (c *Client) Fetch(ctx context.Context, ref string, opts ...RemoteOpt) (imag
 	}
 
 	if fetchCtx.Unpack {
-		return images.Image{}, errors.New("unpack on fetch not supported, try pull")
+		return images.Image{}, errdefs.ErrUnpackNotSupported
 	}
 
 	if fetchCtx.PlatformMatcher == nil {
@@ -656,7 +656,7 @@ func (c *Client) Version(ctx context.Context) (Version, error) {
 	c.connMu.Lock()
 	if c.conn == nil {
 		c.connMu.Unlock()
-		return Version{}, errors.New("no grpc connection available")
+		return Version{}, errdefs.ErrNoGRPC
 	}
 	c.connMu.Unlock()
 	response, err := c.VersionService().Version(ctx, &ptypes.Empty{})

cmd/containerd/command/main.go

@@ -27,6 +27,7 @@ import (
 	"runtime"
 	"time"
 
+	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/log"
 	"github.com/containerd/containerd/mount"
 	"github.com/containerd/containerd/services/server"
@@ -152,7 +153,7 @@ func App() *cli.App {
 			ttrpcAddress = fmt.Sprintf("%s.ttrpc", config.GRPC.Address)
 		)
 		if address == "" {
-			return errors.New("grpc address cannot be empty")
+			return errdefs.ErrEmptyGRCPAddress
 		}
 		log.G(ctx).WithFields(logrus.Fields{
 			"version":  version.Version,

cmd/containerd/command/publish.go

@@ -51,7 +51,7 @@ var publishCommand = cli.Command{
 		ctx := namespaces.WithNamespace(gocontext.Background(), context.String("namespace"))
 		topic := context.String("topic")
 		if topic == "" {
-			return errors.New("topic required to publish event")
+			return errdefs.ErrEmptyTopic
 		}
 		payload, err := getEventPayload(os.Stdin)
 		if err != nil {

cmd/containerd/command/service_windows.go

@@ -18,7 +18,6 @@ package command
 
 import (
 	"bytes"
-	"errors"
 	"fmt"
 	"io/ioutil"
 	"log"
@@ -28,6 +27,7 @@ import (
 	"time"
 	"unsafe"
 
+	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/services/server"
 	"github.com/sirupsen/logrus"
 	"github.com/urfave/cli"
@@ -162,7 +162,7 @@ func (h *etwHook) Fire(e *logrus.Entry) error {
 		etype = windows.EVENTLOG_INFORMATION_TYPE
 		eid = eventDebug
 	default:
-		return errors.New("unknown level")
+		return errdefs.ErrUnknownLevel
 	}
 
 	// If there is additional data, include it as a second string.
@@ -311,7 +311,7 @@ func registerUnregisterService(root string) (bool, error) {
 
 	if unregisterServiceFlag {
 		if registerServiceFlag {
-			return true, errors.New("--register-service and --unregister-service cannot be used together")
+			return true, errdefs.ErrRegisterAndUnregisterService
 		}
 		return true, unregisterService()
 	}

cmd/ctr/commands/containers/containers.go

@@ -28,9 +28,9 @@ import (
 	"github.com/containerd/containerd/cmd/ctr/commands"
 	"github.com/containerd/containerd/cmd/ctr/commands/run"
 	"github.com/containerd/containerd/containers"
+	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/log"
 	"github.com/containerd/typeurl"
-	"github.com/pkg/errors"
 	"github.com/urfave/cli"
 )
 
@@ -65,17 +65,17 @@ var createCommand = cli.Command{
 		if config {
 			id = context.Args().First()
 			if context.NArg() > 1 {
-				return errors.New("with spec config file, only container id should be provided")
+				return errdefs.ErrArgConfigFile
 			}
 		} else {
 			id = context.Args().Get(1)
 			ref = context.Args().First()
 			if ref == "" {
-				return errors.New("image ref must be provided")
+				return errdefs.ErrUnprovidedImageRef
 			}
 		}
 		if id == "" {
-			return errors.New("container id must be provided")
+			return errdefs.ErrEmptyContainerId
 		}
 		client, ctx, cancel, err := commands.NewClient(context)
 		if err != nil {
@@ -168,7 +168,7 @@ var deleteCommand = cli.Command{
 		}
 
 		if context.NArg() == 0 {
-			return errors.New("must specify at least one container to delete")
+			return errdefs.ErrDeleteNoneContainer
 		}
 		for _, arg := range context.Args() {
 			if err := deleteContainer(ctx, client, arg, deleteOpts...); err != nil {
@@ -214,7 +214,7 @@ var setLabelsCommand = cli.Command{
 	Action: func(context *cli.Context) error {
 		containerID, labels := commands.ObjectWithLabelArgs(context)
 		if containerID == "" {
-			return errors.New("container id must be provided")
+			return errdefs.ErrEmptyContainerId
 		}
 		client, ctx, cancel, err := commands.NewClient(context)
 		if err != nil {
@@ -250,7 +250,7 @@ var infoCommand = cli.Command{
 	Action: func(context *cli.Context) error {
 		id := context.Args().First()
 		if id == "" {
-			return errors.New("container id must be provided")
+			return errdefs.ErrEmptyContainerId
 		}
 		client, ctx, cancel, err := commands.NewClient(context)
 		if err != nil {

errdefs/errors.go

@@ -47,6 +47,18 @@ var (
 	ErrFailedPrecondition           = errors.New("failed precondition")
 	ErrUnavailable                  = errors.New("unavailable")
 	ErrNotImplemented               = errors.New("not implemented") // represents not supported and unimplemented
+	ErrNoGRPCAndService             = errors.New("no grpc connection and services is available")
+	ErrNoGRPC                       = errors.New("no grpc connection available")
+	ErrReconnectFailed              = errors.New("unable to reconnect to containerd, no connector available")
+	ErrUnpackNotSupported           = errors.New("unpack on fetch not supported, try pull")
+	ErrEmptyGRCPAddress             = errors.New("grpc address cannot be empty")
+	ErrEmptyTopic                   = errors.New("topic required to publish event")
+	ErrUnknownLevel                 = errors.New("unknown level")
+	ErrRegisterAndUnregisterService = errors.New("--register-service and --unregister-service cannot be used together")
+	ErrArgConfigFile                = errors.New("with spec config file, only container id should be provided")
+	ErrUnprovidedImageRef           = errors.New("image ref must be provided")
+	ErrEmptyContainerId             = errors.New("container id must be provided")
+	ErrDeleteNoneContainer          = errors.New("must specify at least one container to delete")
 )
 
 // IsInvalidArgument returns true if the error is due to an invalid argument