Refactor volume store's error usage

Uses an errors API similar the `net` package.

Signed-off-by: Brian Goff <cpuguy83@gmail.com>

daemon/delete.go

@@ -7,7 +7,7 @@ import (
 
 	"github.com/Sirupsen/logrus"
 	derr "github.com/docker/docker/errors"
-	"github.com/docker/docker/volume/store"
+	volumestore "github.com/docker/docker/volume/store"
 )
 
 // ContainerRmConfig is a holder for passing in runtime config.
@@ -153,7 +153,7 @@ func (daemon *Daemon) VolumeRm(name string) error {
 		return err
 	}
 	if err := daemon.volumes.Remove(v); err != nil {
-		if err == store.ErrVolumeInUse {
+		if volumestore.IsInUse(err) {
 			return derr.ErrorCodeRmVolumeInUse.WithArgs(err)
 		}
 		return derr.ErrorCodeRmVolume.WithArgs(name, err)

daemon/mounts.go

@@ -4,7 +4,7 @@ import (
 	"strings"
 
 	derr "github.com/docker/docker/errors"
-	"github.com/docker/docker/volume/store"
+	volumestore "github.com/docker/docker/volume/store"
 )
 
 func (daemon *Daemon) prepareMountPoints(container *Container) error {
@@ -34,7 +34,7 @@ func (daemon *Daemon) removeMountPoints(container *Container, rm bool) error {
 			// not an error, but an implementation detail.
 			// This prevents docker from logging "ERROR: Volume in use"
 			// where there is another container using the volume.
-			if err != nil && err != store.ErrVolumeInUse {
+			if err != nil && !volumestore.IsInUse(err) {
 				rmErrors = append(rmErrors, err.Error())
 			}
 		}

volume/store/errors.go

@@ -0,0 +1,58 @@
+package store
+
+import "errors"
+
+var (
+	// errVolumeInUse is a typed error returned when trying to remove a volume that is currently in use by a container
+	errVolumeInUse = errors.New("volume is in use")
+	// errNoSuchVolume is a typed error returned if the requested volume doesn't exist in the volume store
+	errNoSuchVolume = errors.New("no such volume")
+	// errInvalidName is a typed error returned when creating a volume with a name that is not valid on the platform
+	errInvalidName = errors.New("volume name is not valid on this platform")
+)
+
+// OpErr is the error type returned by functions in the store package. It describes
+// the operation, volume name, and error.
+type OpErr struct {
+	// Err is the error that occurred during the operation.
+	Err error
+	// Op is the operation which caused the error, such as "create", or "list".
+	Op string
+	// Name is the name of the resource being requested for this op, typically the volume name or the driver name.
+	Name string
+}
+
+// Error satifies the built-in error interface type.
+func (e *OpErr) Error() string {
+	if e == nil {
+		return "<nil>"
+	}
+	s := e.Op
+	if e.Name != "" {
+		s = s + " " + e.Name
+	}
+
+	s = s + ": " + e.Err.Error()
+	return s
+}
+
+// IsInUse returns a boolean indicating whether the error indicates that a
+// volume is in use
+func IsInUse(err error) bool {
+	return isErr(err, errVolumeInUse)
+}
+
+// IsNotExist returns a boolean indicating whether the error indicates that the volume does not exist
+func IsNotExist(err error) bool {
+	return isErr(err, errNoSuchVolume)
+}
+
+func isErr(err error, expected error) bool {
+	switch pe := err.(type) {
+	case nil:
+		return false
+	case *OpErr:
+		err = pe.Err
+	}
+	return err == expected
+}

volume/store/store.go

@@ -1,7 +1,6 @@
 package store
 
 import (
-	"errors"
 	"sync"
 
 	"github.com/Sirupsen/logrus"
@@ -10,15 +9,6 @@ import (
 	"github.com/docker/docker/volume/drivers"
 )
 
-var (
-	// ErrVolumeInUse is a typed error returned when trying to remove a volume that is currently in use by a container
-	ErrVolumeInUse = errors.New("volume is in use")
-	// ErrNoSuchVolume is a typed error returned if the requested volume doesn't exist in the volume store
-	ErrNoSuchVolume = errors.New("no such volume")
-	// ErrInvalidName is a typed error returned when creating a volume with a name that is not valid on the platform
-	ErrInvalidName = errors.New("volume name is not valid on this platform")
-)
-
 // New initializes a VolumeStore to keep
 // reference counting of volumes in the system.
 func New() *VolumeStore {
@@ -81,7 +71,7 @@ func (s *VolumeStore) Create(name, driverName string, opts map[string]string) (v
 
 	vd, err := volumedrivers.GetDriver(driverName)
 	if err != nil {
-		return nil, err
+		return nil, &OpErr{Err: err, Name: driverName, Op: "create"}
 	}
 
 	// Validate the name in a platform-specific manner
@@ -90,12 +80,12 @@ func (s *VolumeStore) Create(name, driverName string, opts map[string]string) (v
 		return nil, err
 	}
 	if !valid {
-		return nil, ErrInvalidName
+		return nil, &OpErr{Err: errInvalidName, Name: name, Op: "create"}
 	}
 
 	v, err := vd.Create(name, opts)
 	if err != nil {
-		return nil, err
+		return nil, &OpErr{Op: "create", Name: name, Err: err}
 	}
 
 	s.set(name, &volumeCounter{v, 0})
@@ -110,7 +100,7 @@ func (s *VolumeStore) Get(name string) (volume.Volume, error) {
 
 	vc, exists := s.get(name)
 	if !exists {
-		return nil, ErrNoSuchVolume
+		return nil, &OpErr{Err: errNoSuchVolume, Name: name, Op: "get"}
 	}
 	return vc.Volume, nil
 }
@@ -124,19 +114,19 @@ func (s *VolumeStore) Remove(v volume.Volume) error {
 	logrus.Debugf("Removing volume reference: driver %s, name %s", v.DriverName(), name)
 	vc, exists := s.get(name)
 	if !exists {
-		return ErrNoSuchVolume
+		return &OpErr{Err: errNoSuchVolume, Name: name, Op: "remove"}
 	}
 
 	if vc.count > 0 {
-		return ErrVolumeInUse
+		return &OpErr{Err: errVolumeInUse, Name: name, Op: "remove"}
 	}
 
 	vd, err := volumedrivers.GetDriver(vc.DriverName())
 	if err != nil {
-		return err
+		return &OpErr{Err: err, Name: vc.DriverName(), Op: "remove"}
 	}
 	if err := vd.Remove(vc.Volume); err != nil {
-		return err
+		return &OpErr{Err: err, Name: name, Op: "remove"}
 	}
 
 	s.remove(name)

volume/store/store_test.go

@@ -1,6 +1,7 @@
 package store
 
 import (
+	"errors"
 	"testing"
 
 	"github.com/docker/docker/volume"
@@ -30,8 +31,8 @@ func TestGet(t *testing.T) {
 		t.Fatalf("Expected fake1 volume, got %v", v)
 	}
 
-	if _, err := s.Get("fake4"); err != ErrNoSuchVolume {
-		t.Fatalf("Expected ErrNoSuchVolume error, got %v", err)
+	if _, err := s.Get("fake4"); !IsNotExist(err) {
+		t.Fatalf("Expected IsNotExist error, got %v", err)
 	}
 }
 
@@ -54,24 +55,25 @@ func TestCreate(t *testing.T) {
 	}
 
 	_, err = s.Create("fakeError", "fake", map[string]string{"error": "create error"})
-	if err == nil || err.Error() != "create error" {
-		t.Fatalf("Expected create error, got %v", err)
+	expected := &OpErr{Op: "create", Name: "fakeError", Err: errors.New("create error")}
+	if err != nil && err.Error() != expected.Error() {
+		t.Fatalf("Expected create fakeError: create error, got %v", err)
 	}
 }
 
 func TestRemove(t *testing.T) {
 	volumedrivers.Register(vt.FakeDriver{}, "fake")
 	s := New()
-	if err := s.Remove(vt.NoopVolume{}); err != ErrNoSuchVolume {
-		t.Fatalf("Expected ErrNoSuchVolume error, got %v", err)
+	if err := s.Remove(vt.NoopVolume{}); !IsNotExist(err) {
+		t.Fatalf("Expected IsNotExist error, got %v", err)
 	}
 	v, err := s.Create("fake1", "fake", nil)
 	if err != nil {
 		t.Fatal(err)
 	}
 	s.Increment(v)
-	if err := s.Remove(v); err != ErrVolumeInUse {
-		t.Fatalf("Expected ErrVolumeInUse error, got %v", err)
+	if err := s.Remove(v); !IsInUse(err) {
+		t.Fatalf("Expected IsInUse error, got %v", err)
 	}
 	s.Decrement(v)
 	if err := s.Remove(v); err != nil {