Revert and bring back B2 gateway implementation (#7224)

This PR is simply a revert of 3265112d04
just for B2 gateway.

cmd/gateway/b2/gateway-b2.go

@@ -0,0 +1,850 @@
+/*
+ * Minio Cloud Storage, (C) 2017, 2018 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package b2
+
+import (
+	"context"
+	"crypto/sha1"
+	"fmt"
+	"hash"
+	"io"
+	"io/ioutil"
+	"net/http"
+
+	"strings"
+	"sync"
+	"time"
+
+	b2 "github.com/minio/blazer/base"
+	"github.com/minio/cli"
+	miniogopolicy "github.com/minio/minio-go/pkg/policy"
+	"github.com/minio/minio/cmd/logger"
+	"github.com/minio/minio/pkg/auth"
+	h2 "github.com/minio/minio/pkg/hash"
+	"github.com/minio/minio/pkg/policy"
+	"github.com/minio/minio/pkg/policy/condition"
+
+	minio "github.com/minio/minio/cmd"
+)
+
+// Supported bucket types by B2 backend.
+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".
+
+  DOMAIN:
+     MINIO_DOMAIN: To enable virtual-host-style requests, set this value to Minio host domain name.
+
+  CACHE:
+     MINIO_CACHE_DRIVES: List of mounted drives or directories delimited by ";".
+     MINIO_CACHE_EXCLUDE: List of cache exclusion patterns delimited by ";".
+     MINIO_CACHE_EXPIRY: Cache expiry duration in days.
+     MINIO_CACHE_MAXUSE: Maximum permitted usage of the cache in percentage (0-100).
+
+EXAMPLES:
+  1. Start minio gateway server for B2 backend.
+     $ export MINIO_ACCESS_KEY=accountID
+     $ export MINIO_SECRET_KEY=applicationKey
+     $ {{.HelpName}}
+
+  2. Start minio gateway server for B2 backend with edge caching enabled.
+     $ export MINIO_ACCESS_KEY=accountID
+     $ export MINIO_SECRET_KEY=applicationKey
+     $ export MINIO_CACHE_DRIVES="/mnt/drive1;/mnt/drive2;/mnt/drive3;/mnt/drive4"
+     $ export MINIO_CACHE_EXCLUDE="bucket1/*;*.png"
+     $ export MINIO_CACHE_EXPIRY=40
+     $ export MINIO_CACHE_MAXUSE=80
+     $ {{.HelpName}}
+`
+	minio.RegisterGatewayCommand(cli.Command{
+		Name:               b2Backend,
+		Usage:              "Backblaze B2",
+		Action:             b2GatewayMain,
+		CustomHelpTemplate: b2GatewayTemplate,
+		HideHelpCommand:    true,
+	})
+}
+
+// Handler for 'minio gateway b2' command line.
+func b2GatewayMain(ctx *cli.Context) {
+	minio.StartGateway(ctx, &B2{})
+}
+
+// B2 implements Minio Gateway
+type B2 struct{}
+
+// Name implements Gateway interface.
+func (g *B2) Name() string {
+	return b2Backend
+}
+
+// NewGatewayLayer returns b2 gateway layer, implements ObjectLayer interface to
+// talk to B2 remote backend.
+func (g *B2) NewGatewayLayer(creds auth.Credentials) (minio.ObjectLayer, error) {
+	ctx := context.Background()
+	client, err := b2.AuthorizeAccount(ctx, creds.AccessKey, creds.SecretKey, b2.Transport(minio.NewCustomHTTPTransport()))
+	if err != nil {
+		return nil, err
+	}
+
+	return &b2Objects{
+		creds:    creds,
+		b2Client: client,
+		ctx:      ctx,
+	}, nil
+}
+
+// Production - Ready for production use.
+func (g *B2) Production() bool {
+	return true
+}
+
+// b2Object implements gateway for Minio and BackBlaze B2 compatible object storage servers.
+type b2Objects struct {
+	minio.GatewayUnsupported
+	mu       sync.Mutex
+	creds    auth.Credentials
+	b2Client *b2.B2
+	ctx      context.Context
+}
+
+// Convert B2 errors to minio object layer errors.
+func b2ToObjectError(err error, params ...string) error {
+	if err == nil {
+		return nil
+	}
+	bucket := ""
+	object := ""
+	uploadID := ""
+	if len(params) >= 1 {
+		bucket = params[0]
+	}
+	if len(params) == 2 {
+		object = params[1]
+	}
+	if len(params) == 3 {
+		uploadID = params[2]
+	}
+
+	// Following code is a non-exhaustive check to convert
+	// B2 errors into S3 compatible errors.
+	//
+	// For a more complete information - https://www.backblaze.com/b2/docs/
+	statusCode, code, msg := b2.Code(err)
+	if statusCode == 0 {
+		// We don't interpret non B2 errors. B2 errors have statusCode
+		// to help us convert them to S3 object errors.
+		return err
+	}
+
+	switch code {
+	case "duplicate_bucket_name":
+		err = minio.BucketAlreadyOwnedByYou{Bucket: bucket}
+	case "bad_request":
+		if object != "" {
+			err = minio.ObjectNameInvalid{
+				Bucket: bucket,
+				Object: object,
+			}
+		} else if bucket != "" {
+			err = minio.BucketNotFound{Bucket: bucket}
+		}
+	case "bad_json":
+		if object != "" {
+			err = minio.ObjectNameInvalid{
+				Bucket: bucket,
+				Object: object,
+			}
+		} else if bucket != "" {
+			err = minio.BucketNameInvalid{Bucket: bucket}
+		}
+	case "bad_bucket_id":
+		err = minio.BucketNotFound{Bucket: bucket}
+	case "file_not_present", "not_found":
+		err = minio.ObjectNotFound{
+			Bucket: bucket,
+			Object: object,
+		}
+	case "cannot_delete_non_empty_bucket":
+		err = minio.BucketNotEmpty{Bucket: bucket}
+	}
+
+	// Special interpretation like this is required for Multipart sessions.
+	if strings.Contains(msg, "No active upload for") && uploadID != "" {
+		err = minio.InvalidUploadID{UploadID: uploadID}
+	}
+
+	return err
+}
+
+// Shutdown saves any gateway metadata to disk
+// if necessary and reload upon next restart.
+func (l *b2Objects) Shutdown(ctx context.Context) error {
+	// TODO
+	return nil
+}
+
+// StorageInfo is not relevant to B2 backend.
+func (l *b2Objects) StorageInfo(ctx context.Context) (si minio.StorageInfo) {
+	return si
+}
+
+// MakeBucket creates a new container on B2 backend.
+func (l *b2Objects) MakeBucketWithLocation(ctx context.Context, bucket, location string) error {
+	// location is ignored for B2 backend.
+
+	// All buckets are set to private by default.
+	_, err := l.b2Client.CreateBucket(l.ctx, bucket, bucketTypePrivate, nil, nil)
+	logger.LogIf(ctx, err)
+	return b2ToObjectError(err, bucket)
+}
+
+func (l *b2Objects) reAuthorizeAccount(ctx context.Context) error {
+	client, err := b2.AuthorizeAccount(l.ctx, l.creds.AccessKey, l.creds.SecretKey, b2.Transport(minio.NewCustomHTTPTransport()))
+	if err != nil {
+		return err
+	}
+	l.mu.Lock()
+	l.b2Client.Update(client)
+	l.mu.Unlock()
+	return nil
+}
+
+// listBuckets is a wrapper similar to ListBuckets, which re-authorizes
+// the account and updates the B2 client safely. Once successfully
+// authorized performs the call again and returns list of buckets.
+// For any errors which are not actionable we return an error.
+func (l *b2Objects) listBuckets(ctx context.Context, err error) ([]*b2.Bucket, error) {
+	if err != nil {
+		if b2.Action(err) != b2.ReAuthenticate {
+			return nil, err
+		}
+		if rerr := l.reAuthorizeAccount(ctx); rerr != nil {
+			return nil, rerr
+		}
+	}
+	bktList, lerr := l.b2Client.ListBuckets(l.ctx)
+	if lerr != nil {
+		return l.listBuckets(ctx, lerr)
+	}
+	return bktList, nil
+}
+
+// Bucket - is a helper which provides a *Bucket instance
+// for performing an API operation. B2 API doesn't
+// provide a direct way to access the bucket so we need
+// to employ following technique.
+func (l *b2Objects) Bucket(ctx context.Context, bucket string) (*b2.Bucket, error) {
+	bktList, err := l.listBuckets(ctx, nil)
+	if err != nil {
+		logger.LogIf(ctx, err)
+		return nil, b2ToObjectError(err, bucket)
+	}
+	for _, bkt := range bktList {
+		if bkt.Name == bucket {
+			return bkt, nil
+		}
+	}
+	return nil, minio.BucketNotFound{Bucket: bucket}
+}
+
+// GetBucketInfo gets bucket metadata..
+func (l *b2Objects) GetBucketInfo(ctx context.Context, bucket string) (bi minio.BucketInfo, err error) {
+	if _, err = l.Bucket(ctx, bucket); err != nil {
+		return bi, err
+	}
+	return minio.BucketInfo{
+		Name:    bucket,
+		Created: time.Unix(0, 0),
+	}, nil
+}
+
+// ListBuckets lists all B2 buckets
+func (l *b2Objects) ListBuckets(ctx context.Context) ([]minio.BucketInfo, error) {
+	bktList, err := l.listBuckets(ctx, nil)
+	if err != nil {
+		return nil, err
+	}
+	var bktInfo []minio.BucketInfo
+	for _, bkt := range bktList {
+		bktInfo = append(bktInfo, minio.BucketInfo{
+			Name:    bkt.Name,
+			Created: time.Unix(0, 0),
+		})
+	}
+	return bktInfo, nil
+}
+
+// DeleteBucket deletes a bucket on B2
+func (l *b2Objects) DeleteBucket(ctx context.Context, bucket string) error {
+	bkt, err := l.Bucket(ctx, bucket)
+	if err != nil {
+		return err
+	}
+	err = bkt.DeleteBucket(l.ctx)
+	logger.LogIf(ctx, err)
+	return b2ToObjectError(err, bucket)
+}
+
+// ListObjects lists all objects in B2 bucket filtered by prefix, returns upto at max 1000 entries at a time.
+func (l *b2Objects) ListObjects(ctx context.Context, bucket string, prefix string, marker string, delimiter string, maxKeys int) (loi minio.ListObjectsInfo, err error) {
+	bkt, err := l.Bucket(ctx, bucket)
+	if err != nil {
+		return loi, err
+	}
+	files, next, lerr := bkt.ListFileNames(l.ctx, maxKeys, marker, prefix, delimiter)
+	if lerr != nil {
+		logger.LogIf(ctx, lerr)
+		return loi, b2ToObjectError(lerr, bucket)
+	}
+	loi.IsTruncated = next != ""
+	loi.NextMarker = next
+	for _, file := range files {
+		switch file.Status {
+		case "folder":
+			loi.Prefixes = append(loi.Prefixes, file.Name)
+		case "upload":
+			loi.Objects = append(loi.Objects, minio.ObjectInfo{
+				Bucket:      bucket,
+				Name:        file.Name,
+				ModTime:     file.Timestamp,
+				Size:        file.Size,
+				ETag:        minio.ToS3ETag(file.Info.ID),
+				ContentType: file.Info.ContentType,
+				UserDefined: file.Info.Info,
+			})
+		}
+	}
+	return loi, nil
+}
+
+// ListObjectsV2 lists all objects in B2 bucket filtered by prefix, returns upto max 1000 entries at a time.
+func (l *b2Objects) ListObjectsV2(ctx context.Context, bucket, prefix, continuationToken, delimiter string, maxKeys int,
+	fetchOwner bool, startAfter string) (loi minio.ListObjectsV2Info, err error) {
+	// fetchOwner is not supported and unused.
+	marker := continuationToken
+	if marker == "" {
+		// B2's continuation token is an object name to "start at" rather than "start after"
+		// startAfter plus the lowest character B2 supports is used so that the startAfter
+		// object isn't included in the results
+		marker = startAfter + " "
+	}
+
+	bkt, err := l.Bucket(ctx, bucket)
+	if err != nil {
+		return loi, err
+	}
+	files, next, lerr := bkt.ListFileNames(l.ctx, maxKeys, marker, prefix, delimiter)
+	if lerr != nil {
+		logger.LogIf(ctx, lerr)
+		return loi, b2ToObjectError(lerr, bucket)
+	}
+	loi.IsTruncated = next != ""
+	loi.ContinuationToken = continuationToken
+	loi.NextContinuationToken = next
+	for _, file := range files {
+		switch file.Status {
+		case "folder":
+			loi.Prefixes = append(loi.Prefixes, file.Name)
+		case "upload":
+			loi.Objects = append(loi.Objects, minio.ObjectInfo{
+				Bucket:      bucket,
+				Name:        file.Name,
+				ModTime:     file.Timestamp,
+				Size:        file.Size,
+				ETag:        minio.ToS3ETag(file.Info.ID),
+				ContentType: file.Info.ContentType,
+				UserDefined: file.Info.Info,
+			})
+		}
+	}
+	return loi, nil
+}
+
+// GetObjectNInfo - returns object info and locked object ReadCloser
+func (l *b2Objects) GetObjectNInfo(ctx context.Context, bucket, object string, rs *minio.HTTPRangeSpec, h http.Header, lockType minio.LockType, opts minio.ObjectOptions) (gr *minio.GetObjectReader, err error) {
+	var objInfo minio.ObjectInfo
+	objInfo, err = l.GetObjectInfo(ctx, bucket, object, opts)
+	if err != nil {
+		return nil, err
+	}
+
+	var startOffset, length int64
+	startOffset, length, err = rs.GetOffsetLength(objInfo.Size)
+	if err != nil {
+		return nil, err
+	}
+
+	pr, pw := io.Pipe()
+	go func() {
+		err := l.GetObject(ctx, bucket, object, startOffset, length, pw, objInfo.ETag, opts)
+		pw.CloseWithError(err)
+	}()
+	// Setup cleanup function to cause the above go-routine to
+	// exit in case of partial read
+	pipeCloser := func() { pr.Close() }
+	return minio.NewGetObjectReaderFromReader(pr, objInfo, pipeCloser), nil
+}
+
+// GetObject reads an object from B2. Supports additional
+// parameters like offset and length which are synonymous with
+// HTTP Range requests.
+//
+// startOffset indicates the starting read location of the object.
+// length indicates the total length of the object.
+func (l *b2Objects) GetObject(ctx context.Context, bucket string, object string, startOffset int64, length int64, writer io.Writer, etag string, opts minio.ObjectOptions) error {
+	bkt, err := l.Bucket(ctx, bucket)
+	if err != nil {
+		return err
+	}
+	reader, err := bkt.DownloadFileByName(l.ctx, object, startOffset, length)
+	if err != nil {
+		logger.LogIf(ctx, err)
+		return b2ToObjectError(err, bucket, object)
+	}
+	defer reader.Close()
+	_, err = io.Copy(writer, reader)
+	logger.LogIf(ctx, err)
+	return b2ToObjectError(err, bucket, object)
+}
+
+// GetObjectInfo reads object info and replies back ObjectInfo
+func (l *b2Objects) GetObjectInfo(ctx context.Context, bucket string, object string, opts minio.ObjectOptions) (objInfo minio.ObjectInfo, err error) {
+	bkt, err := l.Bucket(ctx, bucket)
+	if err != nil {
+		return objInfo, err
+	}
+	f, err := bkt.DownloadFileByName(l.ctx, object, 0, 1)
+	if err != nil {
+		logger.LogIf(ctx, err)
+		return objInfo, b2ToObjectError(err, bucket, object)
+	}
+	f.Close()
+	fi, err := bkt.File(f.ID, object).GetFileInfo(l.ctx)
+	if err != nil {
+		logger.LogIf(ctx, err)
+		return objInfo, b2ToObjectError(err, bucket, object)
+	}
+	return minio.ObjectInfo{
+		Bucket:      bucket,
+		Name:        object,
+		ETag:        minio.ToS3ETag(fi.ID),
+		Size:        fi.Size,
+		ModTime:     fi.Timestamp,
+		ContentType: fi.ContentType,
+		UserDefined: fi.Info,
+	}, nil
+}
+
+// In B2 - You must always include the X-Bz-Content-Sha1 header with
+// your upload request. The value you provide can be:
+// (1) the 40-character hex checksum of the file,
+// (2) the string hex_digits_at_end, or
+// (3) the string do_not_verify.
+// For more reference - https://www.backblaze.com/b2/docs/uploading.html
+//
+// In our case we are going to use (2) option
+const sha1AtEOF = "hex_digits_at_end"
+
+// With the second option mentioned above, you append the 40-character hex sha1
+// to the end of the request body, immediately after the contents of the file
+// being uploaded. Note that the content length is the size of the file plus 40
+// of the original size of the reader.
+//
+// newB2Reader implements a B2 compatible reader by wrapping the hash.Reader into
+// a new io.Reader which will emit out the sha1 hex digits at io.EOF.
+// It also means that your overall content size is now original size + 40 bytes.
+// Additionally this reader also verifies Hash encapsulated inside hash.Reader
+// at io.EOF if the verification failed we return an error and do not send
+// the content to server.
+func newB2Reader(r *h2.Reader, size int64) *Reader {
+	return &Reader{
+		r:        r,
+		size:     size,
+		sha1Hash: sha1.New(),
+	}
+}
+
+// Reader - is a Reader wraps the hash.Reader which will emit out the sha1
+// hex digits at io.EOF. It also means that your overall content size is
+// now original size + 40 bytes. Additionally this reader also verifies
+// Hash encapsulated inside hash.Reader at io.EOF if the verification
+// failed we return an error and do not send the content to server.
+type Reader struct {
+	r        *h2.Reader
+	size     int64
+	sha1Hash hash.Hash
+
+	isEOF bool
+	buf   *strings.Reader
+}
+
+// Size - Returns the total size of Reader.
+func (nb *Reader) Size() int64 { return nb.size + 40 }
+func (nb *Reader) Read(p []byte) (int, error) {
+	if nb.isEOF {
+		return nb.buf.Read(p)
+	}
+	// Read into hash to update the on going checksum.
+	n, err := io.TeeReader(nb.r, nb.sha1Hash).Read(p)
+	if err == io.EOF {
+		// Stream is not corrupted on this end
+		// now fill in the last 40 bytes of sha1 hex
+		// so that the server can verify the stream on
+		// their end.
+		err = nil
+		nb.isEOF = true
+		nb.buf = strings.NewReader(fmt.Sprintf("%x", nb.sha1Hash.Sum(nil)))
+	}
+	return n, err
+}
+
+// PutObject uploads the single upload to B2 backend by using *b2_upload_file* API, uploads upto 5GiB.
+func (l *b2Objects) PutObject(ctx context.Context, bucket string, object string, r *minio.PutObjReader, opts minio.ObjectOptions) (objInfo minio.ObjectInfo, err error) {
+	data := r.Reader
+
+	bkt, err := l.Bucket(ctx, bucket)
+	if err != nil {
+		return objInfo, err
+	}
+	contentType := opts.UserDefined["content-type"]
+	delete(opts.UserDefined, "content-type")
+
+	var u *b2.URL
+	u, err = bkt.GetUploadURL(l.ctx)
+	if err != nil {
+		logger.LogIf(ctx, err)
+		return objInfo, b2ToObjectError(err, bucket, object)
+	}
+
+	hr := newB2Reader(data, data.Size())
+	var f *b2.File
+	f, err = u.UploadFile(l.ctx, hr, int(hr.Size()), object, contentType, sha1AtEOF, opts.UserDefined)
+	if err != nil {
+		logger.LogIf(ctx, err)
+		return objInfo, b2ToObjectError(err, bucket, object)
+	}
+
+	var fi *b2.FileInfo
+	fi, err = f.GetFileInfo(l.ctx)
+	if err != nil {
+		logger.LogIf(ctx, err)
+		return objInfo, b2ToObjectError(err, bucket, object)
+	}
+
+	return minio.ObjectInfo{
+		Bucket:      bucket,
+		Name:        object,
+		ETag:        minio.ToS3ETag(fi.ID),
+		Size:        fi.Size,
+		ModTime:     fi.Timestamp,
+		ContentType: fi.ContentType,
+		UserDefined: fi.Info,
+	}, nil
+}
+
+// DeleteObject deletes a blob in bucket
+func (l *b2Objects) DeleteObject(ctx context.Context, bucket string, object string) error {
+	bkt, err := l.Bucket(ctx, bucket)
+	if err != nil {
+		return err
+	}
+	reader, err := bkt.DownloadFileByName(l.ctx, object, 0, 1)
+	if err != nil {
+		logger.LogIf(ctx, err)
+		return b2ToObjectError(err, bucket, object)
+	}
+	io.Copy(ioutil.Discard, reader)
+	reader.Close()
+	err = bkt.File(reader.ID, object).DeleteFileVersion(l.ctx)
+	logger.LogIf(ctx, err)
+	return b2ToObjectError(err, bucket, object)
+}
+
+// ListMultipartUploads lists all multipart uploads.
+func (l *b2Objects) ListMultipartUploads(ctx context.Context, bucket string, prefix string, keyMarker string, uploadIDMarker string,
+	delimiter string, maxUploads int) (lmi minio.ListMultipartsInfo, err error) {
+	// keyMarker, prefix, delimiter are all ignored, Backblaze B2 doesn't support any
+	// of these parameters only equivalent parameter is uploadIDMarker.
+	bkt, err := l.Bucket(ctx, bucket)
+	if err != nil {
+		return lmi, err
+	}
+	// The maximum number of files to return from this call.
+	// The default value is 100, and the maximum allowed is 100.
+	if maxUploads > 100 {
+		maxUploads = 100
+	}
+	largeFiles, nextMarker, err := bkt.ListUnfinishedLargeFiles(l.ctx, uploadIDMarker, maxUploads)
+	if err != nil {
+		logger.LogIf(ctx, err)
+		return lmi, b2ToObjectError(err, bucket)
+	}
+	lmi = minio.ListMultipartsInfo{
+		MaxUploads: maxUploads,
+	}
+	if nextMarker != "" {
+		lmi.IsTruncated = true
+		lmi.NextUploadIDMarker = nextMarker
+	}
+	for _, largeFile := range largeFiles {
+		lmi.Uploads = append(lmi.Uploads, minio.MultipartInfo{
+			Object:    largeFile.Name,
+			UploadID:  largeFile.ID,
+			Initiated: largeFile.Timestamp,
+		})
+	}
+	return lmi, nil
+}
+
+// NewMultipartUpload upload object in multiple parts, uses B2's LargeFile upload API.
+// Large files can range in size from 5MB to 10TB.
+// Each large file must consist of at least 2 parts, and all of the parts except the
+// last one must be at least 5MB in size. The last part must contain at least one byte.
+// For more information - https://www.backblaze.com/b2/docs/large_files.html
+func (l *b2Objects) NewMultipartUpload(ctx context.Context, bucket string, object string, opts minio.ObjectOptions) (string, error) {
+	var uploadID string
+	bkt, err := l.Bucket(ctx, bucket)
+	if err != nil {
+		return uploadID, err
+	}
+
+	contentType := opts.UserDefined["content-type"]
+	delete(opts.UserDefined, "content-type")
+	lf, err := bkt.StartLargeFile(l.ctx, object, contentType, opts.UserDefined)
+	if err != nil {
+		logger.LogIf(ctx, err)
+		return uploadID, b2ToObjectError(err, bucket, object)
+	}
+
+	return lf.ID, nil
+}
+
+// PutObjectPart puts a part of object in bucket, uses B2's LargeFile upload API.
+func (l *b2Objects) PutObjectPart(ctx context.Context, bucket string, object string, uploadID string, partID int, r *minio.PutObjReader, opts minio.ObjectOptions) (pi minio.PartInfo, err error) {
+	data := r.Reader
+	bkt, err := l.Bucket(ctx, bucket)
+	if err != nil {
+		return pi, err
+	}
+
+	fc, err := bkt.File(uploadID, object).CompileParts(0, nil).GetUploadPartURL(l.ctx)
+	if err != nil {
+		logger.LogIf(ctx, err)
+		return pi, b2ToObjectError(err, bucket, object, uploadID)
+	}
+
+	hr := newB2Reader(data, data.Size())
+	sha1, err := fc.UploadPart(l.ctx, hr, sha1AtEOF, int(hr.Size()), partID)
+	if err != nil {
+		logger.LogIf(ctx, err)
+		return pi, b2ToObjectError(err, bucket, object, uploadID)
+	}
+
+	return minio.PartInfo{
+		PartNumber:   partID,
+		LastModified: minio.UTCNow(),
+		ETag:         minio.ToS3ETag(sha1),
+		Size:         data.Size(),
+	}, nil
+}
+
+// ListObjectParts returns all object parts for specified object in specified bucket, uses B2's LargeFile upload API.
+func (l *b2Objects) ListObjectParts(ctx context.Context, bucket string, object string, uploadID string, partNumberMarker int, maxParts int, opts minio.ObjectOptions) (lpi minio.ListPartsInfo, err error) {
+	bkt, err := l.Bucket(ctx, bucket)
+	if err != nil {
+		return lpi, err
+	}
+	lpi = minio.ListPartsInfo{
+		Bucket:           bucket,
+		Object:           object,
+		UploadID:         uploadID,
+		MaxParts:         maxParts,
+		PartNumberMarker: partNumberMarker,
+	}
+	// startPartNumber must be in the range 1 - 10000 for B2.
+	partNumberMarker++
+	partsList, next, err := bkt.File(uploadID, object).ListParts(l.ctx, partNumberMarker, maxParts)
+	if err != nil {
+		logger.LogIf(ctx, err)
+		return lpi, b2ToObjectError(err, bucket, object, uploadID)
+	}
+	if next != 0 {
+		lpi.IsTruncated = true
+		lpi.NextPartNumberMarker = next
+	}
+	for _, part := range partsList {
+		lpi.Parts = append(lpi.Parts, minio.PartInfo{
+			PartNumber: part.Number,
+			ETag:       minio.ToS3ETag(part.SHA1),
+			Size:       part.Size,
+		})
+	}
+	return lpi, nil
+}
+
+// AbortMultipartUpload aborts a on going multipart upload, uses B2's LargeFile upload API.
+func (l *b2Objects) AbortMultipartUpload(ctx context.Context, bucket string, object string, uploadID string) error {
+	bkt, err := l.Bucket(ctx, bucket)
+	if err != nil {
+		return err
+	}
+	err = bkt.File(uploadID, object).CompileParts(0, nil).CancelLargeFile(l.ctx)
+	logger.LogIf(ctx, err)
+	return b2ToObjectError(err, bucket, object, uploadID)
+}
+
+// CompleteMultipartUpload completes ongoing multipart upload and finalizes object, uses B2's LargeFile upload API.
+func (l *b2Objects) CompleteMultipartUpload(ctx context.Context, bucket string, object string, uploadID string, uploadedParts []minio.CompletePart, opts minio.ObjectOptions) (oi minio.ObjectInfo, err error) {
+	bkt, err := l.Bucket(ctx, bucket)
+	if err != nil {
+		return oi, err
+	}
+	hashes := make(map[int]string)
+	for i, uploadedPart := range uploadedParts {
+		// B2 requires contigous part numbers starting with 1, they do not support
+		// hand picking part numbers, we return an S3 compatible error instead.
+		if i+1 != uploadedPart.PartNumber {
+			logger.LogIf(ctx, minio.InvalidPart{})
+			return oi, b2ToObjectError(minio.InvalidPart{}, bucket, object, uploadID)
+		}
+
+		// Trim "-1" suffix in ETag as PutObjectPart() treats B2 returned SHA1 as ETag.
+		hashes[uploadedPart.PartNumber] = strings.TrimSuffix(uploadedPart.ETag, "-1")
+	}
+
+	if _, err = bkt.File(uploadID, object).CompileParts(0, hashes).FinishLargeFile(l.ctx); err != nil {
+		logger.LogIf(ctx, err)
+		return oi, b2ToObjectError(err, bucket, object, uploadID)
+	}
+
+	return l.GetObjectInfo(ctx, bucket, object, minio.ObjectOptions{})
+}
+
+// SetBucketPolicy - B2 supports 2 types of bucket policies:
+// bucketType.AllPublic - bucketTypeReadOnly means that anybody can download the files is the bucket;
+// bucketType.AllPrivate - bucketTypePrivate means that you need an authorization token to download them.
+// Default is AllPrivate for all buckets.
+func (l *b2Objects) SetBucketPolicy(ctx context.Context, bucket string, bucketPolicy *policy.Policy) error {
+	policyInfo, err := minio.PolicyToBucketAccessPolicy(bucketPolicy)
+	if err != nil {
+		// This should not happen.
+		return b2ToObjectError(err, bucket)
+	}
+
+	var policies []minio.BucketAccessPolicy
+	for prefix, policy := range miniogopolicy.GetPolicies(policyInfo.Statements, bucket, "") {
+		policies = append(policies, minio.BucketAccessPolicy{
+			Prefix: prefix,
+			Policy: policy,
+		})
+	}
+	prefix := bucket + "/*" // For all objects inside the bucket.
+	if len(policies) != 1 {
+		logger.LogIf(ctx, minio.NotImplemented{})
+		return minio.NotImplemented{}
+	}
+	if policies[0].Prefix != prefix {
+		logger.LogIf(ctx, minio.NotImplemented{})
+		return minio.NotImplemented{}
+	}
+	if policies[0].Policy != miniogopolicy.BucketPolicyReadOnly {
+		logger.LogIf(ctx, minio.NotImplemented{})
+		return minio.NotImplemented{}
+	}
+	bkt, err := l.Bucket(ctx, bucket)
+	if err != nil {
+		return err
+	}
+	bkt.Type = bucketTypeReadOnly
+	_, err = bkt.Update(l.ctx)
+	logger.LogIf(ctx, err)
+	return b2ToObjectError(err)
+}
+
+// GetBucketPolicy, returns the current bucketType from B2 backend and convert
+// it into S3 compatible bucket policy info.
+func (l *b2Objects) GetBucketPolicy(ctx context.Context, bucket string) (*policy.Policy, error) {
+	bkt, err := l.Bucket(ctx, bucket)
+	if err != nil {
+		return nil, err
+	}
+
+	// bkt.Type can also be snapshot, but it is only allowed through B2 browser console,
+	// just return back as policy not found for all cases.
+	// CreateBucket always sets the value to allPrivate by default.
+	if bkt.Type != bucketTypeReadOnly {
+		return nil, minio.BucketPolicyNotFound{Bucket: bucket}
+	}
+
+	return &policy.Policy{
+		Version: policy.DefaultVersion,
+		Statements: []policy.Statement{
+			policy.NewStatement(
+				policy.Allow,
+				policy.NewPrincipal("*"),
+				policy.NewActionSet(
+					policy.GetBucketLocationAction,
+					policy.ListBucketAction,
+					policy.GetObjectAction,
+				),
+				policy.NewResourceSet(
+					policy.NewResource(bucket, ""),
+					policy.NewResource(bucket, "*"),
+				),
+				condition.NewFunctions(),
+			),
+		},
+	}, nil
+}
+
+// DeleteBucketPolicy - resets the bucketType of bucket on B2 to 'allPrivate'.
+func (l *b2Objects) DeleteBucketPolicy(ctx context.Context, bucket string) error {
+	bkt, err := l.Bucket(ctx, bucket)
+	if err != nil {
+		return err
+	}
+	bkt.Type = bucketTypePrivate
+	_, err = bkt.Update(l.ctx)
+	logger.LogIf(ctx, err)
+	return b2ToObjectError(err)
+}
+
+// IsCompressionSupported returns whether compression is applicable for this layer.
+func (l *b2Objects) IsCompressionSupported() bool {
+	return false
+}

cmd/gateway/b2/gateway-b2_test.go

@@ -0,0 +1,119 @@
+/*
+ * Minio Cloud Storage, (C) 2017 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package b2
+
+import (
+	"fmt"
+	"testing"
+
+	b2 "github.com/minio/blazer/base"
+
+	minio "github.com/minio/minio/cmd"
+)
+
+// Test b2 object error.
+func TestB2ObjectError(t *testing.T) {
+	testCases := []struct {
+		params      []string
+		b2Err       error
+		expectedErr error
+	}{
+		{
+			[]string{}, nil, nil,
+		},
+		{
+			[]string{}, fmt.Errorf("Not *Error"), fmt.Errorf("Not *Error"),
+		},
+		{
+			[]string{}, fmt.Errorf("Non B2 Error"), fmt.Errorf("Non B2 Error"),
+		},
+		{
+			[]string{"bucket"}, b2.Error{
+				StatusCode: 1,
+				Code:       "duplicate_bucket_name",
+			}, minio.BucketAlreadyOwnedByYou{
+				Bucket: "bucket",
+			},
+		},
+		{
+			[]string{"bucket"}, b2.Error{
+				StatusCode: 1,
+				Code:       "bad_request",
+			}, minio.BucketNotFound{
+				Bucket: "bucket",
+			},
+		},
+		{
+			[]string{"bucket", "object"}, b2.Error{
+				StatusCode: 1,
+				Code:       "bad_request",
+			}, minio.ObjectNameInvalid{
+				Bucket: "bucket",
+				Object: "object",
+			},
+		},
+		{
+			[]string{"bucket"}, b2.Error{
+				StatusCode: 1,
+				Code:       "bad_bucket_id",
+			}, minio.BucketNotFound{Bucket: "bucket"},
+		},
+		{
+			[]string{"bucket", "object"}, b2.Error{
+				StatusCode: 1,
+				Code:       "file_not_present",
+			}, minio.ObjectNotFound{
+				Bucket: "bucket",
+				Object: "object",
+			},
+		},
+		{
+			[]string{"bucket", "object"}, b2.Error{
+				StatusCode: 1,
+				Code:       "not_found",
+			}, minio.ObjectNotFound{
+				Bucket: "bucket",
+				Object: "object",
+			},
+		},
+		{
+			[]string{"bucket"}, b2.Error{
+				StatusCode: 1,
+				Code:       "cannot_delete_non_empty_bucket",
+			}, minio.BucketNotEmpty{
+				Bucket: "bucket",
+			},
+		},
+		{
+			[]string{"bucket", "object", "uploadID"}, b2.Error{
+				StatusCode: 1,
+				Message:    "No active upload for",
+			}, minio.InvalidUploadID{
+				UploadID: "uploadID",
+			},
+		},
+	}
+
+	for i, testCase := range testCases {
+		actualErr := b2ToObjectError(testCase.b2Err, testCase.params...)
+		if actualErr != nil {
+			if actualErr.Error() != testCase.expectedErr.Error() {
+				t.Errorf("Test %d: Expected %s, got %s", i+1, testCase.expectedErr, actualErr)
+			}
+		}
+	}
+}

cmd/gateway/gateway.go

@@ -23,5 +23,9 @@ import (
 	_ "github.com/minio/minio/cmd/gateway/nas"
 	_ "github.com/minio/minio/cmd/gateway/oss"
 	_ "github.com/minio/minio/cmd/gateway/s3"
+
+	// B2 is specifically kept here to avoid re-ordering by goimports,
+	// please ask on github.com/minio/minio/issues before changing this.
+	_ "github.com/minio/minio/cmd/gateway/b2"
 	// Add your gateway here.
 )