Refactor differ into separate package

Add differ options and package with interface.
Update optional values on diff interface to use options.

Signed-off-by: Derek McGowan <derek@mcgstyle.net>

api/next.pb.txt

@@ -1120,6 +1120,34 @@ file {
       type: TYPE_STRING
       json_name: "ref"
     }
+    field {
+      name: "labels"
+      number: 5
+      label: LABEL_REPEATED
+      type: TYPE_MESSAGE
+      type_name: ".containerd.services.diff.v1.DiffRequest.LabelsEntry"
+      json_name: "labels"
+    }
+    nested_type {
+      name: "LabelsEntry"
+      field {
+        name: "key"
+        number: 1
+        label: LABEL_OPTIONAL
+        type: TYPE_STRING
+        json_name: "key"
+      }
+      field {
+        name: "value"
+        number: 2
+        label: LABEL_OPTIONAL
+        type: TYPE_STRING
+        json_name: "value"
+      }
+      options {
+        map_entry: true
+      }
+    }
   }
   message_type {
     name: "DiffResponse"

api/services/diff/v1/diff.pb.go

@@ -30,6 +30,7 @@ import (
 
 import strings "strings"
 import reflect "reflect"
+import github_com_gogo_protobuf_sortkeys "github.com/gogo/protobuf/sortkeys"
 
 import io "io"
 
@@ -78,6 +79,9 @@ type DiffRequest struct {
 	// Ref identifies the pre-commit content store object. This
 	// reference can be used to get the status from the content store.
 	Ref string `protobuf:"bytes,4,opt,name=ref,proto3" json:"ref,omitempty"`
+	// Labels are the labels to apply to the generated content
+	// on content store commit.
+	Labels map[string]string `protobuf:"bytes,5,rep,name=labels" json:"labels,omitempty" protobuf_key:"bytes,1,opt,name=key,proto3" protobuf_val:"bytes,2,opt,name=value,proto3"`
 }
 
 func (m *DiffRequest) Reset()                    { *m = DiffRequest{} }
@@ -334,6 +338,23 @@ func (m *DiffRequest) MarshalTo(dAtA []byte) (int, error) {
 		i = encodeVarintDiff(dAtA, i, uint64(len(m.Ref)))
 		i += copy(dAtA[i:], m.Ref)
 	}
+	if len(m.Labels) > 0 {
+		for k, _ := range m.Labels {
+			dAtA[i] = 0x2a
+			i++
+			v := m.Labels[k]
+			mapSize := 1 + len(k) + sovDiff(uint64(len(k))) + 1 + len(v) + sovDiff(uint64(len(v)))
+			i = encodeVarintDiff(dAtA, i, uint64(mapSize))
+			dAtA[i] = 0xa
+			i++
+			i = encodeVarintDiff(dAtA, i, uint64(len(k)))
+			i += copy(dAtA[i:], k)
+			dAtA[i] = 0x12
+			i++
+			i = encodeVarintDiff(dAtA, i, uint64(len(v)))
+			i += copy(dAtA[i:], v)
+		}
+	}
 	return i, nil
 }
 
@@ -441,6 +462,14 @@ func (m *DiffRequest) Size() (n int) {
 	if l > 0 {
 		n += 1 + l + sovDiff(uint64(l))
 	}
+	if len(m.Labels) > 0 {
+		for k, v := range m.Labels {
+			_ = k
+			_ = v
+			mapEntrySize := 1 + len(k) + sovDiff(uint64(len(k))) + 1 + len(v) + sovDiff(uint64(len(v)))
+			n += mapEntrySize + 1 + sovDiff(uint64(mapEntrySize))
+		}
+	}
 	return n
 }
 
@@ -492,11 +521,22 @@ func (this *DiffRequest) String() string {
 	if this == nil {
 		return "nil"
 	}
+	keysForLabels := make([]string, 0, len(this.Labels))
+	for k, _ := range this.Labels {
+		keysForLabels = append(keysForLabels, k)
+	}
+	github_com_gogo_protobuf_sortkeys.Strings(keysForLabels)
+	mapStringForLabels := "map[string]string{"
+	for _, k := range keysForLabels {
+		mapStringForLabels += fmt.Sprintf("%v: %v,", k, this.Labels[k])
+	}
+	mapStringForLabels += "}"
 	s := strings.Join([]string{`&DiffRequest{`,
 		`Left:` + strings.Replace(fmt.Sprintf("%v", this.Left), "Mount", "containerd_types.Mount", 1) + `,`,
 		`Right:` + strings.Replace(fmt.Sprintf("%v", this.Right), "Mount", "containerd_types.Mount", 1) + `,`,
 		`MediaType:` + fmt.Sprintf("%v", this.MediaType) + `,`,
 		`Ref:` + fmt.Sprintf("%v", this.Ref) + `,`,
+		`Labels:` + mapStringForLabels + `,`,
 		`}`,
 	}, "")
 	return s
@@ -865,6 +905,122 @@ func (m *DiffRequest) Unmarshal(dAtA []byte) error {
 			}
 			m.Ref = string(dAtA[iNdEx:postIndex])
 			iNdEx = postIndex
+		case 5:
+			if wireType != 2 {
+				return fmt.Errorf("proto: wrong wireType = %d for field Labels", wireType)
+			}
+			var msglen int
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowDiff
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := dAtA[iNdEx]
+				iNdEx++
+				msglen |= (int(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+			if msglen < 0 {
+				return ErrInvalidLengthDiff
+			}
+			postIndex := iNdEx + msglen
+			if postIndex > l {
+				return io.ErrUnexpectedEOF
+			}
+			var keykey uint64
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowDiff
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := dAtA[iNdEx]
+				iNdEx++
+				keykey |= (uint64(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+			var stringLenmapkey uint64
+			for shift := uint(0); ; shift += 7 {
+				if shift >= 64 {
+					return ErrIntOverflowDiff
+				}
+				if iNdEx >= l {
+					return io.ErrUnexpectedEOF
+				}
+				b := dAtA[iNdEx]
+				iNdEx++
+				stringLenmapkey |= (uint64(b) & 0x7F) << shift
+				if b < 0x80 {
+					break
+				}
+			}
+			intStringLenmapkey := int(stringLenmapkey)
+			if intStringLenmapkey < 0 {
+				return ErrInvalidLengthDiff
+			}
+			postStringIndexmapkey := iNdEx + intStringLenmapkey
+			if postStringIndexmapkey > l {
+				return io.ErrUnexpectedEOF
+			}
+			mapkey := string(dAtA[iNdEx:postStringIndexmapkey])
+			iNdEx = postStringIndexmapkey
+			if m.Labels == nil {
+				m.Labels = make(map[string]string)
+			}
+			if iNdEx < postIndex {
+				var valuekey uint64
+				for shift := uint(0); ; shift += 7 {
+					if shift >= 64 {
+						return ErrIntOverflowDiff
+					}
+					if iNdEx >= l {
+						return io.ErrUnexpectedEOF
+					}
+					b := dAtA[iNdEx]
+					iNdEx++
+					valuekey |= (uint64(b) & 0x7F) << shift
+					if b < 0x80 {
+						break
+					}
+				}
+				var stringLenmapvalue uint64
+				for shift := uint(0); ; shift += 7 {
+					if shift >= 64 {
+						return ErrIntOverflowDiff
+					}
+					if iNdEx >= l {
+						return io.ErrUnexpectedEOF
+					}
+					b := dAtA[iNdEx]
+					iNdEx++
+					stringLenmapvalue |= (uint64(b) & 0x7F) << shift
+					if b < 0x80 {
+						break
+					}
+				}
+				intStringLenmapvalue := int(stringLenmapvalue)
+				if intStringLenmapvalue < 0 {
+					return ErrInvalidLengthDiff
+				}
+				postStringIndexmapvalue := iNdEx + intStringLenmapvalue
+				if postStringIndexmapvalue > l {
+					return io.ErrUnexpectedEOF
+				}
+				mapvalue := string(dAtA[iNdEx:postStringIndexmapvalue])
+				iNdEx = postStringIndexmapvalue
+				m.Labels[mapkey] = mapvalue
+			} else {
+				var mapvalue string
+				m.Labels[mapkey] = mapvalue
+			}
+			iNdEx = postIndex
 		default:
 			iNdEx = preIndex
 			skippy, err := skipDiff(dAtA[iNdEx:])
@@ -1079,31 +1235,34 @@ func init() {
 }
 
 var fileDescriptorDiff = []byte{
-	// 401 bytes of a gzipped FileDescriptorProto
+	// 454 bytes of a gzipped FileDescriptorProto
-	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0x9c, 0x93, 0x41, 0x8b, 0xda, 0x40,
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0x9c, 0x53, 0x4f, 0x6f, 0xd3, 0x30,
-	0x14, 0xc7, 0x9d, 0x26, 0x5a, 0x1c, 0x2d, 0x94, 0xa1, 0xd0, 0x90, 0xb6, 0x41, 0x72, 0x8a, 0x2d,
+	0x14, 0x9f, 0xfb, 0x0f, 0xf5, 0x75, 0x48, 0xc8, 0x9a, 0x44, 0x14, 0x20, 0xaa, 0x7a, 0xea, 0x40,
-	0x9d, 0x54, 0x0b, 0x1e, 0xea, 0xc5, 0x16, 0xa1, 0xa7, 0x5e, 0x82, 0xa7, 0x16, 0x5a, 0x62, 0x32,
+	0x38, 0xac, 0xa0, 0x09, 0xb6, 0xcb, 0x40, 0x43, 0x5c, 0xc6, 0x25, 0xda, 0x09, 0x24, 0x50, 0xda,
-	0x89, 0x03, 0x9a, 0x19, 0x33, 0xa3, 0xe0, 0xad, 0x9f, 0x63, 0xbf, 0xce, 0x5e, 0x3c, 0xee, 0x71,
+	0xbc, 0x74, 0x16, 0x69, 0xec, 0xd9, 0x6e, 0xa5, 0xdc, 0xf8, 0x2e, 0x7c, 0x14, 0x2e, 0x3b, 0x72,
-	0x8f, 0x6b, 0x3e, 0xc9, 0x92, 0x49, 0xb2, 0x1b, 0x58, 0x70, 0xb3, 0x7b, 0x9a, 0xc7, 0xbc, 0xdf,
+	0xe4, 0x48, 0xfb, 0x49, 0x90, 0x9d, 0x14, 0x22, 0x21, 0x95, 0xc0, 0x29, 0x2f, 0xcf, 0xbf, 0x7f,
-	0xff, 0xbd, 0xff, 0xbc, 0xbc, 0xc0, 0x59, 0x4c, 0xe5, 0x6a, 0xb7, 0xc4, 0x01, 0xdb, 0xb8, 0x01,
+	0xf6, 0xb3, 0xe1, 0x6c, 0xce, 0xcd, 0xd5, 0x72, 0xca, 0x66, 0x62, 0x11, 0xce, 0x44, 0x6e, 0x62,
-	0x4b, 0xa4, 0x4f, 0x13, 0x92, 0x86, 0xf5, 0xd0, 0xe7, 0xd4, 0x15, 0x24, 0xdd, 0xd3, 0x80, 0x08,
+	0x9e, 0xa3, 0x4a, 0xea, 0x65, 0x2c, 0x79, 0xa8, 0x51, 0xad, 0xf8, 0x0c, 0x75, 0x98, 0xf0, 0x34,
-	0x37, 0xa4, 0x51, 0xe4, 0xee, 0x47, 0xea, 0xc4, 0x3c, 0x65, 0x92, 0xa1, 0x77, 0xf7, 0x2c, 0xae,
+	0x0d, 0x57, 0x47, 0xee, 0xcb, 0xa4, 0x12, 0x46, 0xd0, 0x7b, 0xbf, 0xb1, 0x6c, 0x8b, 0x63, 0x6e,
-	0x38, 0xac, 0xf2, 0xfb, 0x91, 0xf9, 0x26, 0x66, 0x31, 0x53, 0x9c, 0x9b, 0x47, 0x85, 0xc4, 0x9c,
+	0x7d, 0x75, 0xe4, 0x1f, 0xcc, 0xc5, 0x5c, 0x38, 0x5c, 0x68, 0xab, 0x92, 0xe2, 0x1f, 0x37, 0x32,
-	0x34, 0x6a, 0x2a, 0x0f, 0x9c, 0x08, 0x77, 0xc3, 0x76, 0x89, 0x2c, 0x75, 0xd3, 0x27, 0xe8, 0x42,
+	0x35, 0x85, 0x44, 0x1d, 0x2e, 0xc4, 0x32, 0x37, 0x15, 0xef, 0xf4, 0x1f, 0x78, 0x09, 0xea, 0x99,
-	0x22, 0x82, 0x94, 0x72, 0xc9, 0xd2, 0x42, 0x6c, 0x6f, 0x61, 0xff, 0x3b, 0xe7, 0xeb, 0x83, 0x47,
+	0xe2, 0xd2, 0x08, 0x55, 0x92, 0x47, 0xd7, 0xb0, 0xff, 0x52, 0xca, 0xac, 0x88, 0xf0, 0x7a, 0x89,
-	0xb6, 0x3b, 0x22, 0x24, 0xfa, 0x02, 0xf5, 0xdc, 0xa5, 0x01, 0x06, 0xc0, 0xe9, 0x8d, 0xdf, 0xe3,
+	0xda, 0xd0, 0x27, 0xd0, 0xb1, 0x29, 0x3d, 0x32, 0x24, 0xe3, 0xc1, 0xe4, 0x3e, 0xab, 0x6d, 0xc3,
-	0xda, 0x33, 0x54, 0x05, 0x3c, 0xbf, 0xab, 0xe0, 0x29, 0x12, 0xb9, 0xb0, 0xa3, 0xdc, 0x08, 0xe3,
+	0x29, 0xb0, 0xf3, 0x5f, 0x0a, 0x91, 0x43, 0xd2, 0x10, 0x7a, 0x2e, 0x8d, 0xf6, 0x5a, 0xc3, 0xf6,
-	0xc5, 0x40, 0x73, 0x7a, 0xe3, 0xb7, 0x0f, 0x35, 0xbf, 0xf2, 0xbc, 0x57, 0x62, 0xf6, 0x4f, 0xf8,
+	0x78, 0x30, 0xb9, 0xfb, 0x27, 0xe7, 0xad, 0x5d, 0x8f, 0x2a, 0xd8, 0xe8, 0x0d, 0xdc, 0xae, 0x2c,
-	0xaa, 0x6c, 0x29, 0x38, 0x4b, 0x04, 0x41, 0x13, 0xf8, 0xd2, 0xe7, 0x7c, 0x4d, 0x49, 0xd8, 0xa8,
+	0xb5, 0x14, 0xb9, 0x46, 0x7a, 0x0c, 0xb7, 0x62, 0x29, 0x33, 0x8e, 0x49, 0x23, 0xdb, 0x2d, 0x78,
-	0x6d, 0x05, 0xdb, 0x17, 0x00, 0xf6, 0xe6, 0x34, 0x8a, 0x2a, 0xef, 0x9f, 0xa0, 0xbe, 0x26, 0x91,
+	0xf4, 0xa5, 0x05, 0x83, 0x73, 0x9e, 0xa6, 0xdb, 0xec, 0x8f, 0xa0, 0x93, 0x61, 0x6a, 0x3c, 0xb2,
-	0x34, 0xc0, 0x79, 0x1f, 0x0a, 0x42, 0x9f, 0x61, 0x3b, 0xa5, 0xf1, 0x4a, 0x3e, 0xe6, 0xba, 0xa0,
+	0x3b, 0x87, 0x03, 0xd1, 0xc7, 0xd0, 0x55, 0x7c, 0x7e, 0x65, 0xfe, 0x96, 0xba, 0x44, 0xd1, 0x07,
-	0xd0, 0x07, 0x08, 0x37, 0x24, 0xa4, 0xfe, 0xbf, 0x3c, 0x67, 0x68, 0x03, 0xe0, 0x74, 0xbd, 0xae,
+	0x00, 0x0b, 0x4c, 0x78, 0xfc, 0xd1, 0xae, 0x79, 0xed, 0x21, 0x19, 0xf7, 0xa3, 0xbe, 0xeb, 0x5c,
-	0xba, 0x59, 0x1c, 0x38, 0x41, 0xaf, 0xa1, 0x96, 0x92, 0xc8, 0xd0, 0xd5, 0x7d, 0x1e, 0xda, 0x33,
+	0x16, 0x12, 0xe9, 0x1d, 0x68, 0x2b, 0x4c, 0xbd, 0x8e, 0xeb, 0xdb, 0x92, 0x5e, 0x40, 0x2f, 0x8b,
-	0xd8, 0x2f, 0xbc, 0x95, 0x8f, 0xac, 0x06, 0xab, 0x35, 0x1d, 0xec, 0xf8, 0x12, 0x40, 0x3d, 0x2f,
+	0xa7, 0x98, 0x69, 0xaf, 0xeb, 0x0c, 0x9e, 0xb1, 0x1d, 0x37, 0x82, 0xd5, 0xb6, 0xc1, 0x2e, 0x1c,
-	0x81, 0xfe, 0xc2, 0xb6, 0x1a, 0x18, 0x1a, 0xe2, 0x33, 0x5b, 0x85, 0xeb, 0xdf, 0xd1, 0xfc, 0xd8,
+	0xed, 0x75, 0x6e, 0x54, 0x11, 0x55, 0x1a, 0xfe, 0x0b, 0x18, 0xd4, 0xda, 0xd6, 0xee, 0x13, 0x16,
-	0x04, 0x2d, 0xad, 0xfd, 0x29, 0xfb, 0x38, 0x67, 0x35, 0xb5, 0x49, 0x9b, 0xc3, 0x06, 0x64, 0x51,
+	0xee, 0xb4, 0xfa, 0x91, 0x2d, 0xe9, 0x01, 0x74, 0x57, 0x71, 0xb6, 0x44, 0xaf, 0xe5, 0x7a, 0xe5,
-	0xfc, 0xc7, 0xe2, 0x78, 0xb2, 0x5a, 0xd7, 0x27, 0xab, 0xf5, 0x3f, 0xb3, 0xc0, 0x31, 0xb3, 0xc0,
+	0xcf, 0x49, 0xeb, 0x39, 0x19, 0x9d, 0xc1, 0x7e, 0xa9, 0x5e, 0x9d, 0xf6, 0x76, 0xc2, 0xed, 0xa6,
-	0x55, 0x66, 0x81, 0x9b, 0xcc, 0x02, 0xbf, 0xbf, 0x3d, 0xeb, 0x27, 0x9b, 0xe6, 0xe7, 0xb2, 0xa3,
+	0x13, 0x9e, 0x7c, 0x25, 0xd0, 0xb1, 0x12, 0xf4, 0x03, 0x74, 0xdd, 0xe4, 0xe8, 0xe1, 0xce, 0xcd,
-	0xb6, 0xf7, 0xeb, 0x6d, 0x00, 0x00, 0x00, 0xff, 0xff, 0x6e, 0x16, 0x1d, 0x04, 0xa9, 0x03, 0x00,
+	0xd4, 0x2f, 0x94, 0xff, 0xb0, 0x09, 0xb4, 0x8a, 0xf6, 0xbe, 0xf2, 0x19, 0x37, 0x3d, 0x2b, 0xff,
-	0x00,
+	0xb0, 0x01, 0xb2, 0x14, 0x7f, 0x75, 0x79, 0xb3, 0x0e, 0xf6, 0xbe, 0xaf, 0x83, 0xbd, 0xcf, 0x9b,
+	0x80, 0xdc, 0x6c, 0x02, 0xf2, 0x6d, 0x13, 0x90, 0x1f, 0x9b, 0x80, 0xbc, 0x3b, 0xf9, 0xaf, 0xd7,
+	0x7e, 0x6a, 0xbf, 0xd3, 0x9e, 0x7b, 0x46, 0x4f, 0x7f, 0x06, 0x00, 0x00, 0xff, 0xff, 0xd6, 0x01,
+	0x51, 0xf0, 0x32, 0x04, 0x00, 0x00,
 }

api/services/diff/v1/diff.proto

@@ -50,6 +50,10 @@ message DiffRequest {
 	// Ref identifies the pre-commit content store object. This
 	// reference can be used to get the status from the content store.
 	string ref = 4;
+
+	// Labels are the labels to apply to the generated content
+	// on content store commit.
+	map<string, string> labels = 5;
 }
 
 message DiffResponse {

client.go

@@ -22,6 +22,7 @@ import (
 	versionservice "github.com/containerd/containerd/api/services/version/v1"
 	"github.com/containerd/containerd/containers"
 	"github.com/containerd/containerd/content"
+	"github.com/containerd/containerd/diff"
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/images"
 	"github.com/containerd/containerd/platforms"
@@ -31,7 +32,6 @@ import (
 	"github.com/containerd/containerd/remotes/docker"
 	"github.com/containerd/containerd/remotes/docker/schema1"
 	contentservice "github.com/containerd/containerd/services/content"
-	"github.com/containerd/containerd/services/diff"
 	diffservice "github.com/containerd/containerd/services/diff"
 	imagesservice "github.com/containerd/containerd/services/images"
 	snapshotservice "github.com/containerd/containerd/services/snapshot"
@@ -439,8 +439,8 @@ func (c *Client) ImageService() images.Store {
 	return imagesservice.NewStoreFromClient(imagesapi.NewImagesClient(c.conn))
 }
 
-// DiffService returns the underlying DiffService
+// DiffService returns the underlying Differ
-func (c *Client) DiffService() diff.DiffService {
+func (c *Client) DiffService() diff.Differ {
 	return diffservice.NewDiffServiceFromClient(diffapi.NewDiffClient(c.conn))
 }
 

cmd/containerd/builtins.go

@@ -2,7 +2,7 @@ package main
 
 // register containerd builtins here
 import (
-	_ "github.com/containerd/containerd/differ"
+	_ "github.com/containerd/containerd/diff/walking"
 	_ "github.com/containerd/containerd/services/containers"
 	_ "github.com/containerd/containerd/services/content"
 	_ "github.com/containerd/containerd/services/diff"

cmd/ctr/utils.go

@@ -28,6 +28,7 @@ import (
 	"github.com/containerd/containerd/api/services/tasks/v1"
 	versionservice "github.com/containerd/containerd/api/services/version/v1"
 	"github.com/containerd/containerd/content"
+	"github.com/containerd/containerd/diff"
 	"github.com/containerd/containerd/images"
 	"github.com/containerd/containerd/namespaces"
 	"github.com/containerd/containerd/platforms"
@@ -35,7 +36,7 @@ import (
 	"github.com/containerd/containerd/remotes/docker"
 	"github.com/containerd/containerd/rootfs"
 	contentservice "github.com/containerd/containerd/services/content"
-	"github.com/containerd/containerd/services/diff"
+	diffservice "github.com/containerd/containerd/services/diff"
 	imagesservice "github.com/containerd/containerd/services/images"
 	namespacesservice "github.com/containerd/containerd/services/namespaces"
 	snapshotservice "github.com/containerd/containerd/services/snapshot"
@@ -169,12 +170,12 @@ func getImageStore(clicontext *cli.Context) (images.Store, error) {
 	return imagesservice.NewStoreFromClient(imagesapi.NewImagesClient(conn)), nil
 }
 
-func getDiffService(context *cli.Context) (diff.DiffService, error) {
+func getDiffService(context *cli.Context) (diff.Differ, error) {
 	conn, err := getGRPCConnection(context)
 	if err != nil {
 		return nil, err
 	}
-	return diff.NewDiffServiceFromClient(diffapi.NewDiffClient(conn)), nil
+	return diffservice.NewDiffServiceFromClient(diffapi.NewDiffClient(conn)), nil
 }
 
 func getVersionService(context *cli.Context) (versionservice.VersionClient, error) {

diff/diff.go

@@ -0,0 +1,69 @@
+package diff
+
+import (
+	"github.com/containerd/containerd/mount"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+	"golang.org/x/net/context"
+)
+
+// Config is used to hold parameters needed for a diff operation
+type Config struct {
+	// MediaType is the type of diff to generate
+	// Default depends on the differ,
+	// i.e. application/vnd.oci.image.layer.v1.tar+gzip
+	MediaType string
+
+	// Reference is the content upload reference
+	// Default will use a random reference string
+	Reference string
+
+	// Labels are the labels to apply to the generated content
+	Labels map[string]string
+}
+
+// Opt is used to configure a diff operation
+type Opt func(*Config) error
+
+// Differ allows the apply and creation of filesystem diffs between mounts
+type Differ interface {
+	// Apply applies the content referred to by the given descriptor to
+	// the provided mount. The method of applying is based on the
+	// implementation and content descriptor. For example, in the common
+	// case the descriptor is a file system difference in tar format,
+	// that tar would be applied on top of the mounts.
+	Apply(ctx context.Context, desc ocispec.Descriptor, mount []mount.Mount) (ocispec.Descriptor, error)
+
+	// DiffMounts computes the difference between two mounts and returns a
+	// descriptor for the computed diff. The options can provide
+	// a ref which can be used to track the content creation of the diff.
+	// The media type which is used to determine the format of the created
+	// content can also be provided as an option.
+	DiffMounts(ctx context.Context, lower, upper []mount.Mount, opts ...Opt) (ocispec.Descriptor, error)
+}
+
+// WithMediaType sets the media type to use for creating the diff, without
+// specifying the differ will choose a default.
+func WithMediaType(m string) Opt {
+	return func(c *Config) error {
+		c.MediaType = m
+		return nil
+	}
+}
+
+// WithReference is used to set the content upload reference used by
+// the diff operation. This allows the caller to track the upload through
+// the content store.
+func WithReference(ref string) Opt {
+	return func(c *Config) error {
+		c.Reference = ref
+		return nil
+	}
+}
+
+// WithLabels is used to set content labels on the created diff content.
+func WithLabels(labels map[string]string) Opt {
+	return func(c *Config) error {
+		c.Labels = labels
+		return nil
+	}
+}

diff/walking/differ.go

@@ -1,14 +1,19 @@
-package differ
+package walking
 
 import (
+	"crypto/rand"
+	"encoding/base64"
+	"fmt"
 	"io"
 	"io/ioutil"
 	"os"
 	"strings"
+	"time"
 
 	"github.com/containerd/containerd/archive"
 	"github.com/containerd/containerd/archive/compression"
 	"github.com/containerd/containerd/content"
+	"github.com/containerd/containerd/diff"
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/images"
 	"github.com/containerd/containerd/metadata"
@@ -46,9 +51,9 @@ type walkingDiff struct {
 
 var emptyDesc = ocispec.Descriptor{}
 
-// NewWalkingDiff is a generic implementation of plugin.Differ.
+// NewWalkingDiff is a generic implementation of diff.Differ.
 // NewWalkingDiff is expected to work with any filesystem.
-func NewWalkingDiff(store content.Store) (plugin.Differ, error) {
+func NewWalkingDiff(store content.Store) (diff.Differ, error) {
 	return &walkingDiff{
 		store: store,
 	}, nil
@@ -122,17 +127,25 @@ func (s *walkingDiff) Apply(ctx context.Context, desc ocispec.Descriptor, mounts
 
 // DiffMounts creates a diff between the given mounts and uploads the result
 // to the content store.
-func (s *walkingDiff) DiffMounts(ctx context.Context, lower, upper []mount.Mount, media, ref string) (ocispec.Descriptor, error) {
+func (s *walkingDiff) DiffMounts(ctx context.Context, lower, upper []mount.Mount, opts ...diff.Opt) (ocispec.Descriptor, error) {
+	var config diff.Config
+	for _, opt := range opts {
+		if err := opt(&config); err != nil {
+			return emptyDesc, err
+		}
+	}
+
+	if config.MediaType == "" {
+		config.MediaType = ocispec.MediaTypeImageLayerGzip
+	}
+
 	var isCompressed bool
-	switch media {
+	switch config.MediaType {
 	case ocispec.MediaTypeImageLayer:
 	case ocispec.MediaTypeImageLayerGzip:
 		isCompressed = true
-	case "":
-		media = ocispec.MediaTypeImageLayerGzip
-		isCompressed = true
 	default:
-		return emptyDesc, errors.Wrapf(errdefs.ErrNotImplemented, "unsupported diff media type: %v", media)
+		return emptyDesc, errors.Wrapf(errdefs.ErrNotImplemented, "unsupported diff media type: %v", config.MediaType)
 	}
 	aDir, err := ioutil.TempDir("", "left-")
 	if err != nil {
@@ -156,34 +169,47 @@ func (s *walkingDiff) DiffMounts(ctx context.Context, lower, upper []mount.Mount
 	}
 	defer mount.Unmount(bDir, 0)
 
-	cw, err := s.store.Writer(ctx, ref, 0, "")
+	if config.Reference == "" {
+		config.Reference = uniqueRef()
+	}
+
+	cw, err := s.store.Writer(ctx, config.Reference, 0, "")
 	if err != nil {
 		return emptyDesc, errors.Wrap(err, "failed to open writer")
 	}
 
-	var opts []content.Opt
 	if isCompressed {
 		dgstr := digest.SHA256.Digester()
 		compressed, err := compression.CompressStream(cw, compression.Gzip)
 		if err != nil {
+			cw.Close()
 			return emptyDesc, errors.Wrap(err, "failed to get compressed stream")
 		}
 		err = archive.WriteDiff(ctx, io.MultiWriter(compressed, dgstr.Hash()), aDir, bDir)
 		compressed.Close()
 		if err != nil {
+			cw.Close()
 			return emptyDesc, errors.Wrap(err, "failed to write compressed diff")
 		}
-		opts = append(opts, content.WithLabels(map[string]string{
+
-			"containerd.io/uncompressed": dgstr.Digest().String(),
+		if config.Labels == nil {
-		}))
+			config.Labels = map[string]string{}
+		}
+		config.Labels["containerd.io/uncompressed"] = dgstr.Digest().String()
 	} else {
 		if err = archive.WriteDiff(ctx, cw, aDir, bDir); err != nil {
+			cw.Close()
 			return emptyDesc, errors.Wrap(err, "failed to write diff")
 		}
 	}
 
+	var commitopts []content.Opt
+	if config.Labels != nil {
+		commitopts = append(commitopts, content.WithLabels(config.Labels))
+	}
+
 	dgst := cw.Digest()
-	if err := cw.Commit(ctx, 0, dgst, opts...); err != nil {
+	if err := cw.Commit(ctx, 0, dgst, commitopts...); err != nil {
 		return emptyDesc, errors.Wrap(err, "failed to commit")
 	}
 
@@ -193,7 +219,7 @@ func (s *walkingDiff) DiffMounts(ctx context.Context, lower, upper []mount.Mount
 	}
 
 	return ocispec.Descriptor{
-		MediaType: media,
+		MediaType: config.MediaType,
 		Size:      info.Size,
 		Digest:    info.Digest,
 	}, nil
@@ -209,3 +235,11 @@ func (rc *readCounter) Read(p []byte) (n int, err error) {
 	rc.c += int64(n)
 	return
 }
+
+func uniqueRef() string {
+	t := time.Now()
+	var b [3]byte
+	// Ignore read failures, just decreases uniqueness
+	rand.Read(b[:])
+	return fmt.Sprintf("%d-%s", t.UnixNano(), base64.URLEncoding.EncodeToString(b[:]))
+}

plugin/differ.go

@@ -1,13 +0,0 @@
-package plugin
-
-import (
-	"github.com/containerd/containerd/mount"
-	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
-	"golang.org/x/net/context"
-)
-
-// Differ allows the apply and creation of filesystem diffs between mounts
-type Differ interface {
-	Apply(ctx context.Context, desc ocispec.Descriptor, mount []mount.Mount) (ocispec.Descriptor, error)
-	DiffMounts(ctx context.Context, lower, upper []mount.Mount, media, ref string) (ocispec.Descriptor, error)
-}

rootfs/apply.go

@@ -6,9 +6,9 @@ import (
 	"fmt"
 	"time"
 
+	"github.com/containerd/containerd/diff"
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/log"
-	"github.com/containerd/containerd/mount"
 	"github.com/containerd/containerd/snapshot"
 	"github.com/opencontainers/go-digest"
 	"github.com/opencontainers/image-spec/identity"
@@ -17,11 +17,6 @@ import (
 	"golang.org/x/net/context"
 )
 
-// Applier is used to apply a descriptor of a layer diff on top of mounts.
-type Applier interface {
-	Apply(context.Context, ocispec.Descriptor, []mount.Mount) (ocispec.Descriptor, error)
-}
-
 // Layer represents the descriptors for a layer diff. These descriptions
 // include the descriptor for the uncompressed tar diff as well as a blob
 // used to transport that tar. The blob descriptor may or may not describe
@@ -35,7 +30,7 @@ type Layer struct {
 // The returned result is a chain id digest representing all the applied layers.
 // Layers are applied in order they are given, making the first layer the
 // bottom-most layer in the layer chain.
-func ApplyLayers(ctx context.Context, layers []Layer, sn snapshot.Snapshotter, a Applier) (digest.Digest, error) {
+func ApplyLayers(ctx context.Context, layers []Layer, sn snapshot.Snapshotter, a diff.Differ) (digest.Digest, error) {
 	var chain []digest.Digest
 	for _, layer := range layers {
 		if _, err := ApplyLayer(ctx, layer, chain, sn, a); err != nil {
@@ -51,7 +46,7 @@ func ApplyLayers(ctx context.Context, layers []Layer, sn snapshot.Snapshotter, a
 // ApplyLayer applies a single layer on top of the given provided layer chain,
 // using the provided snapshotter and applier. If the layer was unpacked true
 // is returned, if the layer already exists false is returned.
-func ApplyLayer(ctx context.Context, layer Layer, chain []digest.Digest, sn snapshot.Snapshotter, a Applier) (bool, error) {
+func ApplyLayer(ctx context.Context, layer Layer, chain []digest.Digest, sn snapshot.Snapshotter, a diff.Differ, opts ...snapshot.Opt) (bool, error) {
 	var (
 		parent  = identity.ChainID(chain)
 		chainID = identity.ChainID(append(chain, layer.Diff.Digest))

rootfs/diff.go

@@ -3,25 +3,18 @@ package rootfs
 import (
 	"fmt"
 
+	"github.com/containerd/containerd/diff"
 	"github.com/containerd/containerd/mount"
 	"github.com/containerd/containerd/snapshot"
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"golang.org/x/net/context"
 )
 
-// MountDiffer computes the difference between two mounts and returns a
-// descriptor for the computed diff. The provided ref can be used to track
-// the content creation of the diff and media type is used to determine the
-// format of the created content.
-type MountDiffer interface {
-	DiffMounts(ctx context.Context, lower, upper []mount.Mount, media, ref string) (ocispec.Descriptor, error)
-}
-
 // Diff creates a layer diff for the given snapshot identifier from the parent
 // of the snapshot. A content ref is provided to track the progress of the
 // content creation and the provided snapshotter and mount differ are used
 // for calculating the diff. The descriptor for the layer diff is returned.
-func Diff(ctx context.Context, snapshotID, contentRef string, sn snapshot.Snapshotter, md MountDiffer) (ocispec.Descriptor, error) {
+func Diff(ctx context.Context, snapshotID string, sn snapshot.Snapshotter, d diff.Differ, opts ...diff.Opt) (ocispec.Descriptor, error) {
 	info, err := sn.Stat(ctx, snapshotID)
 	if err != nil {
 		return ocispec.Descriptor{}, err
@@ -49,5 +42,5 @@ func Diff(ctx context.Context, snapshotID, contentRef string, sn snapshot.Snapsh
 		defer sn.Remove(ctx, lowerKey)
 	}
 
-	return md.DiffMounts(ctx, lower, upper, ocispec.MediaTypeImageLayerGzip, contentRef)
+	return d.DiffMounts(ctx, lower, upper, opts...)
 }

services/diff/client.go

@@ -3,20 +3,15 @@ package diff
 import (
 	diffapi "github.com/containerd/containerd/api/services/diff/v1"
 	"github.com/containerd/containerd/api/types"
+	"github.com/containerd/containerd/diff"
 	"github.com/containerd/containerd/mount"
-	"github.com/containerd/containerd/rootfs"
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"golang.org/x/net/context"
 )
 
-type DiffService interface {
-	rootfs.Applier
-	rootfs.MountDiffer
-}
-
 // NewApplierFromClient returns a new Applier which communicates
 // over a GRPC connection.
-func NewDiffServiceFromClient(client diffapi.DiffClient) DiffService {
+func NewDiffServiceFromClient(client diffapi.DiffClient) diff.Differ {
 	return &remote{
 		client: client,
 	}
@@ -38,12 +33,19 @@ func (r *remote) Apply(ctx context.Context, diff ocispec.Descriptor, mounts []mo
 	return toDescriptor(resp.Applied), nil
 }
 
-func (r *remote) DiffMounts(ctx context.Context, a, b []mount.Mount, media, ref string) (ocispec.Descriptor, error) {
+func (r *remote) DiffMounts(ctx context.Context, a, b []mount.Mount, opts ...diff.Opt) (ocispec.Descriptor, error) {
+	var config diff.Config
+	for _, opt := range opts {
+		if err := opt(&config); err != nil {
+			return ocispec.Descriptor{}, err
+		}
+	}
 	req := &diffapi.DiffRequest{
 		Left:      fromMounts(a),
 		Right:     fromMounts(b),
-		MediaType: media,
+		MediaType: config.MediaType,
-		Ref:       ref,
+		Ref:       config.Reference,
+		Labels:    config.Labels,
 	}
 	resp, err := r.client.Diff(ctx, req)
 	if err != nil {

services/diff/service.go

@@ -3,6 +3,7 @@ package diff
 import (
 	diffapi "github.com/containerd/containerd/api/services/diff/v1"
 	"github.com/containerd/containerd/api/types"
+	"github.com/containerd/containerd/diff"
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/mount"
 	"github.com/containerd/containerd/plugin"
@@ -39,7 +40,7 @@ func init() {
 			}
 
 			orderedNames := ic.Config.(*config).Order
-			ordered := make([]plugin.Differ, len(orderedNames))
+			ordered := make([]diff.Differ, len(orderedNames))
 			for i, n := range orderedNames {
 				differp, ok := differs[n]
 				if !ok {
@@ -50,7 +51,7 @@ func init() {
 					return nil, errors.Wrapf(err, "could not load required differ due plugin init error: %s", n)
 				}
 
-				ordered[i] = differ.(plugin.Differ)
+				ordered[i] = differ.(diff.Differ)
 			}
 
 			return &service{
@@ -61,7 +62,7 @@ func init() {
 }
 
 type service struct {
-	differs []plugin.Differ
+	differs []diff.Differ
 }
 
 func (s *service) Register(gs *grpc.Server) error {
@@ -102,8 +103,19 @@ func (s *service) Diff(ctx context.Context, dr *diffapi.DiffRequest) (*diffapi.D
 		bMounts = toMounts(dr.Right)
 	)
 
+	var opts []diff.Opt
+	if dr.MediaType != "" {
+		opts = append(opts, diff.WithMediaType(dr.MediaType))
+	}
+	if dr.Ref != "" {
+		opts = append(opts, diff.WithReference(dr.Ref))
+	}
+	if dr.Labels != nil {
+		opts = append(opts, diff.WithLabels(dr.Labels))
+	}
+
 	for _, differ := range s.differs {
-		ocidesc, err = differ.DiffMounts(ctx, aMounts, bMounts, dr.MediaType, dr.Ref)
+		ocidesc, err = differ.DiffMounts(ctx, aMounts, bMounts, opts...)
 		if !errdefs.IsNotImplemented(err) {
 			break
 		}

task.go

@@ -15,6 +15,7 @@ import (
 	"github.com/containerd/containerd/api/services/tasks/v1"
 	"github.com/containerd/containerd/api/types"
 	"github.com/containerd/containerd/content"
+	"github.com/containerd/containerd/diff"
 	"github.com/containerd/containerd/errdefs"
 	"github.com/containerd/containerd/mount"
 	"github.com/containerd/containerd/plugin"
@@ -482,7 +483,7 @@ func (t *task) checkpointTask(ctx context.Context, index *v1.Index, request *tas
 }
 
 func (t *task) checkpointRWSnapshot(ctx context.Context, index *v1.Index, snapshotterName string, id string) error {
-	rw, err := rootfs.Diff(ctx, id, fmt.Sprintf("checkpoint-rw-%s", id), t.client.SnapshotService(snapshotterName), t.client.DiffService())
+	rw, err := rootfs.Diff(ctx, id, t.client.SnapshotService(snapshotterName), t.client.DiffService(), diff.WithReference(fmt.Sprintf("checkpoint-rw-%s", id)))
 	if err != nil {
 		return err
 	}