Fix for issue 664: https://github.com/docker/distribution/issues/664

Errors thrown by storage drivers don't have the name of the driver, causing user
confusion about whether the error is coming from Docker or from a storage driver.
This change adds the storage driver name to each error message.

This required changing ErrUnsupportedDriver to a type, leading to code changes
whenever ErrUnsupportedDriver is used.  The tests check whether the driver name
appears in the error message.

Signed-off-by: Amit Shukla <amit.shukla@docker.com>

docs/storage/blobserver.go

@@ -36,16 +36,15 @@ func (bs *blobServer) ServeBlob(ctx context.Context, w http.ResponseWriter, r *h
 
 	redirectURL, err := bs.driver.URLFor(ctx, path, map[string]interface{}{"method": r.Method})
 
-	switch err {
+	if err == nil {
-	case nil:
 		if bs.redirect {
 			// Redirect to storage URL.
 			http.Redirect(w, r, redirectURL, http.StatusTemporaryRedirect)
 			return err
 		}
+	}
 
-		fallthrough
+	if _, ok := err.(*driver.ErrUnsupportedMethod); ok {
-	case driver.ErrUnsupportedMethod:
 		// Fallback to serving the content directly.
 		br, err := newFileReader(ctx, bs.driver, path, desc.Size)
 		if err != nil {

docs/storage/driver/base/base.go

@@ -50,16 +50,40 @@ type Base struct {
 	storagedriver.StorageDriver
 }
 
+// Format errors received from the storage driver
+func (base *Base) setDriverName(e error) error {
+	if e != nil {
+		if actualErr, ok := e.(storagedriver.ErrUnsupportedMethod); ok {
+			actualErr.DriverName = base.StorageDriver.Name()
+			return actualErr
+		}
+		if actualErr, ok := e.(storagedriver.PathNotFoundError); ok {
+			actualErr.DriverName = base.StorageDriver.Name()
+			return actualErr
+		}
+		if actualErr, ok := e.(storagedriver.InvalidPathError); ok {
+			actualErr.DriverName = base.StorageDriver.Name()
+			return actualErr
+		}
+		if actualErr, ok := e.(storagedriver.InvalidOffsetError); ok {
+			actualErr.DriverName = base.StorageDriver.Name()
+			return actualErr
+		}
+	}
+	return e
+}
+
 // GetContent wraps GetContent of underlying storage driver.
 func (base *Base) GetContent(ctx context.Context, path string) ([]byte, error) {
 	ctx, done := context.WithTrace(ctx)
 	defer done("%s.GetContent(%q)", base.Name(), path)
 
 	if !storagedriver.PathRegexp.MatchString(path) {
-		return nil, storagedriver.InvalidPathError{Path: path}
+		return nil, storagedriver.InvalidPathError{Path: path, DriverName: base.StorageDriver.Name()}
 	}
 
-	return base.StorageDriver.GetContent(ctx, path)
+	b, e := base.StorageDriver.GetContent(ctx, path)
+	return b, base.setDriverName(e)
 }
 
 // PutContent wraps PutContent of underlying storage driver.
@@ -68,10 +92,10 @@ func (base *Base) PutContent(ctx context.Context, path string, content []byte) e
 	defer done("%s.PutContent(%q)", base.Name(), path)
 
 	if !storagedriver.PathRegexp.MatchString(path) {
-		return storagedriver.InvalidPathError{Path: path}
+		return storagedriver.InvalidPathError{Path: path, DriverName: base.StorageDriver.Name()}
 	}
 
-	return base.StorageDriver.PutContent(ctx, path, content)
+	return base.setDriverName(base.StorageDriver.PutContent(ctx, path, content))
 }
 
 // ReadStream wraps ReadStream of underlying storage driver.
@@ -80,14 +104,15 @@ func (base *Base) ReadStream(ctx context.Context, path string, offset int64) (io
 	defer done("%s.ReadStream(%q, %d)", base.Name(), path, offset)
 
 	if offset < 0 {
-		return nil, storagedriver.InvalidOffsetError{Path: path, Offset: offset}
+		return nil, storagedriver.InvalidOffsetError{Path: path, Offset: offset, DriverName: base.StorageDriver.Name()}
 	}
 
 	if !storagedriver.PathRegexp.MatchString(path) {
-		return nil, storagedriver.InvalidPathError{Path: path}
+		return nil, storagedriver.InvalidPathError{Path: path, DriverName: base.StorageDriver.Name()}
 	}
 
-	return base.StorageDriver.ReadStream(ctx, path, offset)
+	rc, e := base.StorageDriver.ReadStream(ctx, path, offset)
+	return rc, base.setDriverName(e)
 }
 
 // WriteStream wraps WriteStream of underlying storage driver.
@@ -96,14 +121,15 @@ func (base *Base) WriteStream(ctx context.Context, path string, offset int64, re
 	defer done("%s.WriteStream(%q, %d)", base.Name(), path, offset)
 
 	if offset < 0 {
-		return 0, storagedriver.InvalidOffsetError{Path: path, Offset: offset}
+		return 0, storagedriver.InvalidOffsetError{Path: path, Offset: offset, DriverName: base.StorageDriver.Name()}
 	}
 
 	if !storagedriver.PathRegexp.MatchString(path) {
-		return 0, storagedriver.InvalidPathError{Path: path}
+		return 0, storagedriver.InvalidPathError{Path: path, DriverName: base.StorageDriver.Name()}
 	}
 
-	return base.StorageDriver.WriteStream(ctx, path, offset, reader)
+	i64, e := base.StorageDriver.WriteStream(ctx, path, offset, reader)
+	return i64, base.setDriverName(e)
 }
 
 // Stat wraps Stat of underlying storage driver.
@@ -112,10 +138,11 @@ func (base *Base) Stat(ctx context.Context, path string) (storagedriver.FileInfo
 	defer done("%s.Stat(%q)", base.Name(), path)
 
 	if !storagedriver.PathRegexp.MatchString(path) {
-		return nil, storagedriver.InvalidPathError{Path: path}
+		return nil, storagedriver.InvalidPathError{Path: path, DriverName: base.StorageDriver.Name()}
 	}
 
-	return base.StorageDriver.Stat(ctx, path)
+	fi, e := base.StorageDriver.Stat(ctx, path)
+	return fi, base.setDriverName(e)
 }
 
 // List wraps List of underlying storage driver.
@@ -124,10 +151,11 @@ func (base *Base) List(ctx context.Context, path string) ([]string, error) {
 	defer done("%s.List(%q)", base.Name(), path)
 
 	if !storagedriver.PathRegexp.MatchString(path) && path != "/" {
-		return nil, storagedriver.InvalidPathError{Path: path}
+		return nil, storagedriver.InvalidPathError{Path: path, DriverName: base.StorageDriver.Name()}
 	}
 
-	return base.StorageDriver.List(ctx, path)
+	str, e := base.StorageDriver.List(ctx, path)
+	return str, base.setDriverName(e)
 }
 
 // Move wraps Move of underlying storage driver.
@@ -136,12 +164,12 @@ func (base *Base) Move(ctx context.Context, sourcePath string, destPath string)
 	defer done("%s.Move(%q, %q", base.Name(), sourcePath, destPath)
 
 	if !storagedriver.PathRegexp.MatchString(sourcePath) {
-		return storagedriver.InvalidPathError{Path: sourcePath}
+		return storagedriver.InvalidPathError{Path: sourcePath, DriverName: base.StorageDriver.Name()}
 	} else if !storagedriver.PathRegexp.MatchString(destPath) {
-		return storagedriver.InvalidPathError{Path: destPath}
+		return storagedriver.InvalidPathError{Path: destPath, DriverName: base.StorageDriver.Name()}
 	}
 
-	return base.StorageDriver.Move(ctx, sourcePath, destPath)
+	return base.setDriverName(base.StorageDriver.Move(ctx, sourcePath, destPath))
 }
 
 // Delete wraps Delete of underlying storage driver.
@@ -150,10 +178,10 @@ func (base *Base) Delete(ctx context.Context, path string) error {
 	defer done("%s.Delete(%q)", base.Name(), path)
 
 	if !storagedriver.PathRegexp.MatchString(path) {
-		return storagedriver.InvalidPathError{Path: path}
+		return storagedriver.InvalidPathError{Path: path, DriverName: base.StorageDriver.Name()}
 	}
 
-	return base.StorageDriver.Delete(ctx, path)
+	return base.setDriverName(base.StorageDriver.Delete(ctx, path))
 }
 
 // URLFor wraps URLFor of underlying storage driver.
@@ -162,8 +190,9 @@ func (base *Base) URLFor(ctx context.Context, path string, options map[string]in
 	defer done("%s.URLFor(%q)", base.Name(), path)
 
 	if !storagedriver.PathRegexp.MatchString(path) {
-		return "", storagedriver.InvalidPathError{Path: path}
+		return "", storagedriver.InvalidPathError{Path: path, DriverName: base.StorageDriver.Name()}
 	}
 
-	return base.StorageDriver.URLFor(ctx, path, options)
+	str, e := base.StorageDriver.URLFor(ctx, path, options)
+	return str, base.setDriverName(e)
 }

docs/storage/driver/filesystem/driver.go

@@ -248,7 +248,7 @@ func (d *driver) Delete(ctx context.Context, subPath string) error {
 // URLFor returns a URL which may be used to retrieve the content stored at the given path.
 // May return an UnsupportedMethodErr in certain StorageDriver implementations.
 func (d *driver) URLFor(ctx context.Context, path string, options map[string]interface{}) (string, error) {
-	return "", storagedriver.ErrUnsupportedMethod
+	return "", new(storagedriver.ErrUnsupportedMethod)
 }
 
 // fullPath returns the absolute path of a key within the Driver's storage.

docs/storage/driver/inmemory/driver.go

@@ -258,5 +258,5 @@ func (d *driver) Delete(ctx context.Context, path string) error {
 // URLFor returns a URL which may be used to retrieve the content stored at the given path.
 // May return an UnsupportedMethodErr in certain StorageDriver implementations.
 func (d *driver) URLFor(ctx context.Context, path string, options map[string]interface{}) (string, error) {
-	return "", storagedriver.ErrUnsupportedMethod
+	return "", new(storagedriver.ErrUnsupportedMethod)
 }

docs/storage/driver/oss/oss.go

@@ -748,7 +748,7 @@ func (d *driver) URLFor(ctx context.Context, path string, options map[string]int
 	if ok {
 		methodString, ok = method.(string)
 		if !ok || (methodString != "GET" && methodString != "HEAD") {
-			return "", storagedriver.ErrUnsupportedMethod
+			return "", new(storagedriver.ErrUnsupportedMethod)
 		}
 	}
 

docs/storage/driver/rados/rados.go

@@ -496,7 +496,7 @@ func (d *driver) Delete(ctx context.Context, objectPath string) error {
 // URLFor returns a URL which may be used to retrieve the content stored at the given path.
 // May return an UnsupportedMethodErr in certain StorageDriver implementations.
 func (d *driver) URLFor(ctx context.Context, path string, options map[string]interface{}) (string, error) {
-	return "", storagedriver.ErrUnsupportedMethod
+	return "", new(storagedriver.ErrUnsupportedMethod)
 }
 
 // Generate a blob identifier

docs/storage/driver/s3/s3.go

@@ -759,7 +759,7 @@ func (d *driver) URLFor(ctx context.Context, path string, options map[string]int
 	if ok {
 		methodString, ok = method.(string)
 		if !ok || (methodString != "GET" && methodString != "HEAD") {
-			return "", storagedriver.ErrUnsupportedMethod
+			return "", new(storagedriver.ErrUnsupportedMethod)
 		}
 	}
 

docs/storage/driver/storagedriver.go

@@ -1,7 +1,6 @@
 package driver
 
 import (
-	"errors"
 	"fmt"
 	"io"
 	"regexp"
@@ -93,24 +92,32 @@ type StorageDriver interface {
 var PathRegexp = regexp.MustCompile(`^(/[A-Za-z0-9._-]+)+$`)
 
 // ErrUnsupportedMethod may be returned in the case where a StorageDriver implementation does not support an optional method.
-var ErrUnsupportedMethod = errors.New("unsupported method")
+type ErrUnsupportedMethod struct {
+	DriverName string
+}
+
+func (err ErrUnsupportedMethod) Error() string {
+	return fmt.Sprintf("[%s] unsupported method", err.DriverName)
+}
 
 // PathNotFoundError is returned when operating on a nonexistent path.
 type PathNotFoundError struct {
 	Path       string
+	DriverName string
 }
 
 func (err PathNotFoundError) Error() string {
-	return fmt.Sprintf("Path not found: %s", err.Path)
+	return fmt.Sprintf("[%s] Path not found: %s", err.DriverName, err.Path)
 }
 
 // InvalidPathError is returned when the provided path is malformed.
 type InvalidPathError struct {
 	Path       string
+	DriverName string
 }
 
 func (err InvalidPathError) Error() string {
-	return fmt.Sprintf("Invalid path: %s", err.Path)
+	return fmt.Sprintf("[%s] Invalid path: %s", err.DriverName, err.Path)
 }
 
 // InvalidOffsetError is returned when attempting to read or write from an
@@ -118,8 +125,9 @@ func (err InvalidPathError) Error() string {
 type InvalidOffsetError struct {
 	Path       string
 	Offset     int64
+	DriverName string
 }
 
 func (err InvalidOffsetError) Error() string {
-	return fmt.Sprintf("Invalid offset: %d for path: %s", err.Offset, err.Path)
+	return fmt.Sprintf("[%s] Invalid offset: %d for path: %s", err.DriverName, err.Offset, err.Path)
 }

docs/storage/driver/swift/swift.go

@@ -658,14 +658,14 @@ func (d *driver) Delete(ctx context.Context, path string) error {
 // URLFor returns a URL which may be used to retrieve the content stored at the given path.
 func (d *driver) URLFor(ctx context.Context, path string, options map[string]interface{}) (string, error) {
 	if d.SecretKey == "" {
-		return "", storagedriver.ErrUnsupportedMethod
+		return "", storagedriver.ErrUnsupportedMethod{}
 	}
 
 	methodString := "GET"
 	method, ok := options["method"]
 	if ok {
 		if methodString, ok = method.(string); !ok {
-			return "", storagedriver.ErrUnsupportedMethod
+			return "", storagedriver.ErrUnsupportedMethod{}
 		}
 	}
 
@@ -684,7 +684,7 @@ func (d *driver) URLFor(ctx context.Context, path string, options map[string]int
 	}
 
 	if !supported {
-		return "", storagedriver.ErrUnsupportedMethod
+		return "", storagedriver.ErrUnsupportedMethod{}
 	}
 
 	expiresTime := time.Now().Add(20 * time.Minute)

docs/storage/driver/testsuites/testsuites.go

@@ -10,6 +10,7 @@ import (
 	"os"
 	"path"
 	"sort"
+	"strings"
 	"sync"
 	"testing"
 	"time"
@@ -145,10 +146,12 @@ func (suite *DriverSuite) TestInvalidPaths(c *check.C) {
 		defer suite.StorageDriver.Delete(suite.ctx, firstPart(filename))
 		c.Assert(err, check.NotNil)
 		c.Assert(err, check.FitsTypeOf, storagedriver.InvalidPathError{})
+		c.Assert(strings.Contains(err.Error(), suite.Name()), check.Equals, true)
 
 		_, err = suite.StorageDriver.GetContent(suite.ctx, filename)
 		c.Assert(err, check.NotNil)
 		c.Assert(err, check.FitsTypeOf, storagedriver.InvalidPathError{})
+		c.Assert(strings.Contains(err.Error(), suite.Name()), check.Equals, true)
 	}
 }
 
@@ -205,6 +208,7 @@ func (suite *DriverSuite) TestReadNonexistent(c *check.C) {
 	_, err := suite.StorageDriver.GetContent(suite.ctx, filename)
 	c.Assert(err, check.NotNil)
 	c.Assert(err, check.FitsTypeOf, storagedriver.PathNotFoundError{})
+	c.Assert(strings.Contains(err.Error(), suite.Name()), check.Equals, true)
 }
 
 // TestWriteReadStreams1 tests a simple write-read streaming workflow.
@@ -321,6 +325,7 @@ func (suite *DriverSuite) TestReadStreamWithOffset(c *check.C) {
 	c.Assert(err.(storagedriver.InvalidOffsetError).Offset, check.Equals, int64(-1))
 	c.Assert(err.(storagedriver.InvalidOffsetError).Path, check.Equals, filename)
 	c.Assert(reader, check.IsNil)
+	c.Assert(strings.Contains(err.Error(), suite.Name()), check.Equals, true)
 
 	// Read past the end of the content and make sure we get a reader that
 	// returns 0 bytes and io.EOF
@@ -443,6 +448,7 @@ func (suite *DriverSuite) testContinueStreamAppend(c *check.C, chunkSize int64)
 	c.Assert(err, check.FitsTypeOf, storagedriver.InvalidOffsetError{})
 	c.Assert(err.(storagedriver.InvalidOffsetError).Path, check.Equals, filename)
 	c.Assert(err.(storagedriver.InvalidOffsetError).Offset, check.Equals, int64(-1))
+	c.Assert(strings.Contains(err.Error(), suite.Name()), check.Equals, true)
 }
 
 // TestReadNonexistentStream tests that reading a stream for a nonexistent path
@@ -453,10 +459,12 @@ func (suite *DriverSuite) TestReadNonexistentStream(c *check.C) {
 	_, err := suite.StorageDriver.ReadStream(suite.ctx, filename, 0)
 	c.Assert(err, check.NotNil)
 	c.Assert(err, check.FitsTypeOf, storagedriver.PathNotFoundError{})
+	c.Assert(strings.Contains(err.Error(), suite.Name()), check.Equals, true)
 
 	_, err = suite.StorageDriver.ReadStream(suite.ctx, filename, 64)
 	c.Assert(err, check.NotNil)
 	c.Assert(err, check.FitsTypeOf, storagedriver.PathNotFoundError{})
+	c.Assert(strings.Contains(err.Error(), suite.Name()), check.Equals, true)
 }
 
 // TestList checks the returned list of keys after populating a directory tree.
@@ -517,6 +525,7 @@ func (suite *DriverSuite) TestMove(c *check.C) {
 	_, err = suite.StorageDriver.GetContent(suite.ctx, sourcePath)
 	c.Assert(err, check.NotNil)
 	c.Assert(err, check.FitsTypeOf, storagedriver.PathNotFoundError{})
+	c.Assert(strings.Contains(err.Error(), suite.Name()), check.Equals, true)
 }
 
 // TestMoveOverwrite checks that a moved object no longer exists at the source
@@ -546,6 +555,7 @@ func (suite *DriverSuite) TestMoveOverwrite(c *check.C) {
 	_, err = suite.StorageDriver.GetContent(suite.ctx, sourcePath)
 	c.Assert(err, check.NotNil)
 	c.Assert(err, check.FitsTypeOf, storagedriver.PathNotFoundError{})
+	c.Assert(strings.Contains(err.Error(), suite.Name()), check.Equals, true)
 }
 
 // TestMoveNonexistent checks that moving a nonexistent key fails and does not
@@ -563,6 +573,7 @@ func (suite *DriverSuite) TestMoveNonexistent(c *check.C) {
 	err = suite.StorageDriver.Move(suite.ctx, sourcePath, destPath)
 	c.Assert(err, check.NotNil)
 	c.Assert(err, check.FitsTypeOf, storagedriver.PathNotFoundError{})
+	c.Assert(strings.Contains(err.Error(), suite.Name()), check.Equals, true)
 
 	received, err := suite.StorageDriver.GetContent(suite.ctx, destPath)
 	c.Assert(err, check.IsNil)
@@ -600,6 +611,7 @@ func (suite *DriverSuite) TestDelete(c *check.C) {
 	_, err = suite.StorageDriver.GetContent(suite.ctx, filename)
 	c.Assert(err, check.NotNil)
 	c.Assert(err, check.FitsTypeOf, storagedriver.PathNotFoundError{})
+	c.Assert(strings.Contains(err.Error(), suite.Name()), check.Equals, true)
 }
 
 // TestURLFor checks that the URLFor method functions properly, but only if it
@@ -614,7 +626,7 @@ func (suite *DriverSuite) TestURLFor(c *check.C) {
 	c.Assert(err, check.IsNil)
 
 	url, err := suite.StorageDriver.URLFor(suite.ctx, filename, nil)
-	if err == storagedriver.ErrUnsupportedMethod {
+	if _, ok := err.(*storagedriver.ErrUnsupportedMethod); ok {
 		return
 	}
 	c.Assert(err, check.IsNil)
@@ -628,7 +640,7 @@ func (suite *DriverSuite) TestURLFor(c *check.C) {
 	c.Assert(read, check.DeepEquals, contents)
 
 	url, err = suite.StorageDriver.URLFor(suite.ctx, filename, map[string]interface{}{"method": "HEAD"})
-	if err == storagedriver.ErrUnsupportedMethod {
+	if _, ok := err.(*storagedriver.ErrUnsupportedMethod); ok {
 		return
 	}
 	c.Assert(err, check.IsNil)
@@ -644,6 +656,7 @@ func (suite *DriverSuite) TestDeleteNonexistent(c *check.C) {
 	err := suite.StorageDriver.Delete(suite.ctx, filename)
 	c.Assert(err, check.NotNil)
 	c.Assert(err, check.FitsTypeOf, storagedriver.PathNotFoundError{})
+	c.Assert(strings.Contains(err.Error(), suite.Name()), check.Equals, true)
 }
 
 // TestDeleteFolder checks that deleting a folder removes all child elements.
@@ -671,6 +684,7 @@ func (suite *DriverSuite) TestDeleteFolder(c *check.C) {
 	_, err = suite.StorageDriver.GetContent(suite.ctx, path.Join(dirname, filename1))
 	c.Assert(err, check.NotNil)
 	c.Assert(err, check.FitsTypeOf, storagedriver.PathNotFoundError{})
+	c.Assert(strings.Contains(err.Error(), suite.Name()), check.Equals, true)
 
 	_, err = suite.StorageDriver.GetContent(suite.ctx, path.Join(dirname, filename2))
 	c.Assert(err, check.IsNil)
@@ -684,14 +698,17 @@ func (suite *DriverSuite) TestDeleteFolder(c *check.C) {
 	_, err = suite.StorageDriver.GetContent(suite.ctx, path.Join(dirname, filename1))
 	c.Assert(err, check.NotNil)
 	c.Assert(err, check.FitsTypeOf, storagedriver.PathNotFoundError{})
+	c.Assert(strings.Contains(err.Error(), suite.Name()), check.Equals, true)
 
 	_, err = suite.StorageDriver.GetContent(suite.ctx, path.Join(dirname, filename2))
 	c.Assert(err, check.NotNil)
 	c.Assert(err, check.FitsTypeOf, storagedriver.PathNotFoundError{})
+	c.Assert(strings.Contains(err.Error(), suite.Name()), check.Equals, true)
 
 	_, err = suite.StorageDriver.GetContent(suite.ctx, path.Join(dirname, filename3))
 	c.Assert(err, check.NotNil)
 	c.Assert(err, check.FitsTypeOf, storagedriver.PathNotFoundError{})
+	c.Assert(strings.Contains(err.Error(), suite.Name()), check.Equals, true)
 }
 
 // TestStatCall runs verifies the implementation of the storagedriver's Stat call.
@@ -707,11 +724,13 @@ func (suite *DriverSuite) TestStatCall(c *check.C) {
 	fi, err := suite.StorageDriver.Stat(suite.ctx, dirPath)
 	c.Assert(err, check.NotNil)
 	c.Assert(err, check.FitsTypeOf, storagedriver.PathNotFoundError{})
+	c.Assert(strings.Contains(err.Error(), suite.Name()), check.Equals, true)
 	c.Assert(fi, check.IsNil)
 
 	fi, err = suite.StorageDriver.Stat(suite.ctx, filePath)
 	c.Assert(err, check.NotNil)
 	c.Assert(err, check.FitsTypeOf, storagedriver.PathNotFoundError{})
+	c.Assert(strings.Contains(err.Error(), suite.Name()), check.Equals, true)
 	c.Assert(fi, check.IsNil)
 
 	err = suite.StorageDriver.PutContent(suite.ctx, filePath, content)