Implement ListMultipartUploads, ListObjectParts for GCS gateway (#6377)

ListMultipartUploads implementation is meant for docker-registry
use-case only. It lists only the first upload with a prefix matching
the object being uploaded.

cmd/gateway/gcs/gateway-gcs.go

@@ -20,11 +20,15 @@ import (
 	"context"
 	"encoding/base64"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
 	"math"
 	"net/http"
+	"path"
+	"strconv"
+
 	"os"
 	"regexp"
 	"strings"
@@ -936,14 +940,84 @@ func (l *gcsGateway) NewMultipartUpload(ctx context.Context, bucket string, key
 	return uploadID, nil
 }
 
-// ListMultipartUploads - lists all multipart uploads.
+// ListMultipartUploads - lists the (first) multipart upload for an object
+// matched _exactly_ by the prefix
 func (l *gcsGateway) ListMultipartUploads(ctx context.Context, bucket string, prefix string, keyMarker string, uploadIDMarker string, delimiter string, maxUploads int) (minio.ListMultipartsInfo, error) {
+	// List objects under <bucket>/gcsMinioMultipartPathV1
+	it := l.client.Bucket(bucket).Objects(ctx, &storage.Query{
+		Prefix: gcsMinioMultipartPathV1,
+	})
+
+	var uploads []minio.MultipartInfo
+
+	for {
+		attrs, err := it.Next()
+		if err == iterator.Done {
+			break
+		}
+
+		if err != nil {
+			logger.LogIf(ctx, err)
 			return minio.ListMultipartsInfo{
 				KeyMarker:      keyMarker,
 				UploadIDMarker: uploadIDMarker,
 				MaxUploads:     maxUploads,
 				Prefix:         prefix,
 				Delimiter:      delimiter,
+			}, gcsToObjectError(err)
+		}
+
+		// Skip entries other than gcs.json
+		if !strings.HasSuffix(attrs.Name, gcsMinioMultipartMeta) {
+			continue
+		}
+
+		// Extract multipart upload information from gcs.json
+		obj := l.client.Bucket(bucket).Object(attrs.Name)
+		objReader, rErr := obj.NewReader(ctx)
+		if rErr != nil {
+			logger.LogIf(ctx, rErr)
+			return minio.ListMultipartsInfo{}, rErr
+		}
+		defer objReader.Close()
+
+		var mpMeta gcsMultipartMetaV1
+		dec := json.NewDecoder(objReader)
+		decErr := dec.Decode(&mpMeta)
+		if decErr != nil {
+			logger.LogIf(ctx, decErr)
+			return minio.ListMultipartsInfo{}, decErr
+		}
+
+		if prefix == mpMeta.Object {
+			// Extract uploadId
+			// E.g minio.sys.tmp/multipart/v1/d063ad89-fdc4-4ea3-a99e-22dba98151f5/gcs.json
+			components := strings.SplitN(attrs.Name, "/", 5)
+			if len(components) != 5 {
+				compErr := errors.New("Invalid multipart upload format")
+				logger.LogIf(ctx, compErr)
+				return minio.ListMultipartsInfo{}, compErr
+			}
+			upload := minio.MultipartInfo{
+				Object:    mpMeta.Object,
+				UploadID:  components[3],
+				Initiated: attrs.Created,
+			}
+			uploads = []minio.MultipartInfo{upload}
+			break
+		}
+	}
+
+	return minio.ListMultipartsInfo{
+		KeyMarker:          keyMarker,
+		UploadIDMarker:     uploadIDMarker,
+		MaxUploads:         maxUploads,
+		Prefix:             prefix,
+		Delimiter:          delimiter,
+		Uploads:            uploads,
+		NextKeyMarker:      "",
+		NextUploadIDMarker: "",
+		IsTruncated:        false,
 	}, nil
 }
 
@@ -987,9 +1061,91 @@ func (l *gcsGateway) PutObjectPart(ctx context.Context, bucket string, key strin
 
 }
 
+// gcsGetPartInfo returns PartInfo of a given object part
+func gcsGetPartInfo(ctx context.Context, attrs *storage.ObjectAttrs) (minio.PartInfo, error) {
+	components := strings.SplitN(attrs.Name, "/", 5)
+	if len(components) != 5 {
+		logger.LogIf(ctx, errors.New("Invalid multipart upload format"))
+		return minio.PartInfo{}, errors.New("Invalid multipart upload format")
+	}
+
+	partComps := strings.SplitN(components[4], ".", 2)
+	if len(partComps) != 2 {
+		logger.LogIf(ctx, errors.New("Invalid multipart part format"))
+		return minio.PartInfo{}, errors.New("Invalid multipart part format")
+	}
+
+	partNum, pErr := strconv.Atoi(partComps[0])
+	if pErr != nil {
+		logger.LogIf(ctx, pErr)
+		return minio.PartInfo{}, errors.New("Invalid part number")
+	}
+
+	return minio.PartInfo{
+		PartNumber:   partNum,
+		LastModified: attrs.Updated,
+		Size:         attrs.Size,
+		ETag:         partComps[1],
+	}, nil
+}
+
 //  ListObjectParts returns all object parts for specified object in specified bucket
 func (l *gcsGateway) ListObjectParts(ctx context.Context, bucket string, key string, uploadID string, partNumberMarker int, maxParts int) (minio.ListPartsInfo, error) {
-	return minio.ListPartsInfo{}, l.checkUploadIDExists(ctx, bucket, key, uploadID)
+	it := l.client.Bucket(bucket).Objects(ctx, &storage.Query{
+		Prefix: path.Join(gcsMinioMultipartPathV1, uploadID),
+	})
+
+	var (
+		count     int
+		partInfos []minio.PartInfo
+	)
+
+	isTruncated := true
+	for count < maxParts {
+		attrs, err := it.Next()
+		if err == iterator.Done {
+			isTruncated = false
+			break
+		}
+
+		if err != nil {
+			logger.LogIf(ctx, err)
+			return minio.ListPartsInfo{}, gcsToObjectError(err)
+		}
+
+		if strings.HasSuffix(attrs.Name, gcsMinioMultipartMeta) {
+			continue
+		}
+
+		partInfo, pErr := gcsGetPartInfo(ctx, attrs)
+		if pErr != nil {
+			logger.LogIf(ctx, pErr)
+			return minio.ListPartsInfo{}, pErr
+		}
+
+		if partInfo.PartNumber <= partNumberMarker {
+			continue
+		}
+
+		partInfos = append(partInfos, partInfo)
+		count++
+	}
+
+	nextPartNumberMarker := 0
+	if isTruncated {
+		nextPartNumberMarker = partInfos[maxParts-1].PartNumber
+	}
+
+	return minio.ListPartsInfo{
+		Bucket:               bucket,
+		Object:               key,
+		UploadID:             uploadID,
+		PartNumberMarker:     partNumberMarker,
+		NextPartNumberMarker: nextPartNumberMarker,
+		MaxParts:             maxParts,
+		Parts:                partInfos,
+		IsTruncated:          isTruncated,
+	}, nil
 }
 
 // Called by AbortMultipartUpload and CompleteMultipartUpload for cleaning up.