storj/storagenode/pieces/store.go

// Copyright (C) 2019 Storj Labs, Inc.
// See LICENSE for copying information.

package pieces

import (
	"context"
	"io"
	"os"
	"time"

	"github.com/zeebo/errs"
	"go.uber.org/zap"
	"gopkg.in/spacemonkeygo/monkit.v2"

	"storj.io/storj/pkg/pb"
	"storj.io/storj/pkg/storj"
	"storj.io/storj/private/memory"
	"storj.io/storj/storage"
	"storj.io/storj/storage/filestore"
)

const (
	preallocSize = 4 * memory.MiB
)

var (
	// Error is the default error class.
	Error = errs.Class("pieces error")

	mon = monkit.Package()
)

// Info contains all the information we need to know about a Piece to manage them.
type Info struct {
	SatelliteID storj.NodeID

	PieceID         storj.PieceID
	PieceSize       int64
	PieceCreation   time.Time
	PieceExpiration time.Time

	OrderLimit      *pb.OrderLimit
	UplinkPieceHash *pb.PieceHash
}

// ExpiredInfo is a fully namespaced piece id
type ExpiredInfo struct {
	SatelliteID storj.NodeID
	PieceID     storj.PieceID

	// This can be removed when we no longer need to support the pieceinfo db. Its only purpose
	// is to keep track of whether expired entries came from piece_expirations or pieceinfo.
	InPieceInfo bool
}

// PieceExpirationDB stores information about pieces with expiration dates.
//
// architecture: Database
type PieceExpirationDB interface {
	// GetExpired gets piece IDs that expire or have expired before the given time
	GetExpired(ctx context.Context, expiresBefore time.Time, limit int64) ([]ExpiredInfo, error)
	// SetExpiration sets an expiration time for the given piece ID on the given satellite
	SetExpiration(ctx context.Context, satellite storj.NodeID, pieceID storj.PieceID, expiresAt time.Time) error
	// DeleteExpiration removes an expiration record for the given piece ID on the given satellite
	DeleteExpiration(ctx context.Context, satellite storj.NodeID, pieceID storj.PieceID) (found bool, err error)
	// DeleteFailed marks an expiration record as having experienced a failure in deleting the
	// piece from the disk
	DeleteFailed(ctx context.Context, satelliteID storj.NodeID, pieceID storj.PieceID, failedAt time.Time) error
	// Trash marks a piece as in the trash
	Trash(ctx context.Context, satelliteID storj.NodeID, pieceID storj.PieceID) error
	// RestoreTrash marks all piece as not being in trash
	RestoreTrash(ctx context.Context, satelliteID storj.NodeID) error
}

// V0PieceInfoDB stores meta information about pieces stored with storage format V0 (where
// metadata goes in the "pieceinfo" table in the storagenodedb). The actual pieces are stored
// behind something providing the storage.Blobs interface.
//
// architecture: Database
type V0PieceInfoDB interface {
	// Get returns Info about a piece.
	Get(ctx context.Context, satelliteID storj.NodeID, pieceID storj.PieceID) (*Info, error)
	// Delete deletes Info about a piece.
	Delete(ctx context.Context, satelliteID storj.NodeID, pieceID storj.PieceID) error
	// DeleteFailed marks piece deletion from disk failed
	DeleteFailed(ctx context.Context, satelliteID storj.NodeID, pieceID storj.PieceID, failedAt time.Time) error
	// GetExpired gets piece IDs stored with storage format V0 that expire or have expired
	// before the given time
	GetExpired(ctx context.Context, expiredAt time.Time, limit int64) ([]ExpiredInfo, error)
	// WalkSatelliteV0Pieces executes walkFunc for each locally stored piece, stored
	// with storage format V0 in the namespace of the given satellite. If walkFunc returns a
	// non-nil error, WalkSatelliteV0Pieces will stop iterating and return the error
	// immediately. The ctx parameter is intended specifically to allow canceling iteration
	// early.
	WalkSatelliteV0Pieces(ctx context.Context, blobStore storage.Blobs, satellite storj.NodeID, walkFunc func(StoredPieceAccess) error) error
}

// V0PieceInfoDBForTest is like V0PieceInfoDB, but adds on the Add() method so
// that test environments with V0 piece data can be set up.
type V0PieceInfoDBForTest interface {
	V0PieceInfoDB

	// Add inserts Info to the database. This is only a valid thing to do, now,
	// during tests, to replicate the environment of a storage node not yet fully
	// migrated to V1 storage.
	Add(context.Context, *Info) error
}

// PieceSpaceUsedDB stores the most recent totals from the space used cache
//
// architecture: Database
type PieceSpaceUsedDB interface {
	// Init creates the one total record if it doesn't already exist
	Init(ctx context.Context) error
	// GetTotal returns the total space used by all pieces stored on disk
	GetTotal(ctx context.Context) (int64, error)
	// GetTotalsForAllSatellites returns how much total space used by pieces stored on disk for each satelliteID
	GetTotalsForAllSatellites(ctx context.Context) (map[storj.NodeID]int64, error)
	// UpdateTotal updates the record for total spaced used with a new value
	UpdateTotal(ctx context.Context, newTotal int64) error
	// UpdateTotalsForAllSatellites updates each record for total spaced used with a new value for each satelliteID
	UpdateTotalsForAllSatellites(ctx context.Context, newTotalsBySatellites map[storj.NodeID]int64) error
}

// StoredPieceAccess allows inspection and manipulation of a piece during iteration with
// WalkSatellitePieces-type methods.
type StoredPieceAccess interface {
	storage.BlobInfo

	// PieceID gives the pieceID of the piece
	PieceID() storj.PieceID
	// Satellite gives the nodeID of the satellite which owns the piece
	Satellite() (storj.NodeID, error)
	// ContentSize gives the size of the piece content (not including the piece header, if
	// applicable)
	ContentSize(ctx context.Context) (int64, error)
	// CreationTime returns the piece creation time as given in the original PieceHash (which is
	// likely not the same as the file mtime). For non-FormatV0 pieces, this requires opening
	// the file and unmarshaling the piece header. If exact precision is not required, ModTime()
	// may be a better solution.
	CreationTime(ctx context.Context) (time.Time, error)
	// ModTime returns a less-precise piece creation time than CreationTime, but is generally
	// much faster. For non-FormatV0 pieces, this gets the piece creation time from to the
	// filesystem instead of the piece header.
	ModTime(ctx context.Context) (time.Time, error)
}

// Store implements storing pieces onto a blob storage implementation.
//
// architecture: Database
type Store struct {
	log            *zap.Logger
	blobs          storage.Blobs
	v0PieceInfo    V0PieceInfoDB
	expirationInfo PieceExpirationDB
	spaceUsedDB    PieceSpaceUsedDB
}

// StoreForTest is a wrapper around Store to be used only in test scenarios. It enables writing
// pieces with older storage formats
type StoreForTest struct {
	*Store
}

// NewStore creates a new piece store
func NewStore(log *zap.Logger, blobs storage.Blobs, v0PieceInfo V0PieceInfoDB, expirationInfo PieceExpirationDB, pieceSpaceUsedDB PieceSpaceUsedDB) *Store {
	return &Store{
		log:            log,
		blobs:          blobs,
		v0PieceInfo:    v0PieceInfo,
		expirationInfo: expirationInfo,
		spaceUsedDB:    pieceSpaceUsedDB,
	}
}

// Writer returns a new piece writer.
func (store *Store) Writer(ctx context.Context, satellite storj.NodeID, pieceID storj.PieceID) (_ *Writer, err error) {
	defer mon.Task()(&ctx)(&err)
	blobWriter, err := store.blobs.Create(ctx, storage.BlobRef{
		Namespace: satellite.Bytes(),
		Key:       pieceID.Bytes(),
	}, preallocSize.Int64())
	if err != nil {
		return nil, Error.Wrap(err)
	}

	writer, err := NewWriter(blobWriter, store.blobs, satellite)
	return writer, Error.Wrap(err)
}

// WriterForFormatVersion allows opening a piece writer with a specified storage format version.
// This is meant to be used externally only in test situations (thus the StoreForTest receiver
// type).
func (store StoreForTest) WriterForFormatVersion(ctx context.Context, satellite storj.NodeID, pieceID storj.PieceID, formatVersion storage.FormatVersion) (_ *Writer, err error) {
	defer mon.Task()(&ctx)(&err)

	blobRef := storage.BlobRef{
		Namespace: satellite.Bytes(),
		Key:       pieceID.Bytes(),
	}
	var blobWriter storage.BlobWriter
	switch formatVersion {
	case filestore.FormatV0:
		fStore, ok := store.blobs.(interface {
			TestCreateV0(ctx context.Context, ref storage.BlobRef) (_ storage.BlobWriter, err error)
		})
		if !ok {
			return nil, Error.New("can't make a WriterForFormatVersion with this blob store (%T)", store.blobs)
		}
		blobWriter, err = fStore.TestCreateV0(ctx, blobRef)
	case filestore.FormatV1:
		blobWriter, err = store.blobs.Create(ctx, blobRef, preallocSize.Int64())
	default:
		return nil, Error.New("please teach me how to make V%d pieces", formatVersion)
	}
	if err != nil {
		return nil, Error.Wrap(err)
	}
	writer, err := NewWriter(blobWriter, store.blobs, satellite)
	return writer, Error.Wrap(err)
}

// Reader returns a new piece reader.
func (store *Store) Reader(ctx context.Context, satellite storj.NodeID, pieceID storj.PieceID) (_ *Reader, err error) {
	defer mon.Task()(&ctx)(&err)
	blob, err := store.blobs.Open(ctx, storage.BlobRef{
		Namespace: satellite.Bytes(),
		Key:       pieceID.Bytes(),
	})
	if err != nil {
		if os.IsNotExist(err) {
			return nil, err
		}
		return nil, Error.Wrap(err)
	}

	reader, err := NewReader(blob)
	return reader, Error.Wrap(err)
}

// ReaderWithStorageFormat returns a new piece reader for a located piece, which avoids the
// potential need to check multiple storage formats to find the right blob.
func (store *Store) ReaderWithStorageFormat(ctx context.Context, satellite storj.NodeID, pieceID storj.PieceID, formatVersion storage.FormatVersion) (_ *Reader, err error) {
	defer mon.Task()(&ctx)(&err)
	ref := storage.BlobRef{Namespace: satellite.Bytes(), Key: pieceID.Bytes()}
	blob, err := store.blobs.OpenWithStorageFormat(ctx, ref, formatVersion)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, err
		}
		return nil, Error.Wrap(err)
	}

	reader, err := NewReader(blob)
	return reader, Error.Wrap(err)
}

// Delete deletes the specified piece.
func (store *Store) Delete(ctx context.Context, satellite storj.NodeID, pieceID storj.PieceID) (err error) {
	defer mon.Task()(&ctx)(&err)
	err = store.blobs.Delete(ctx, storage.BlobRef{
		Namespace: satellite.Bytes(),
		Key:       pieceID.Bytes(),
	})
	if err != nil {
		return Error.Wrap(err)
	}

	// delete records in both the piece_expirations and pieceinfo DBs, wherever we find it.
	// both of these calls should return no error if the requested record is not found.
	if store.expirationInfo != nil {
		_, err = store.expirationInfo.DeleteExpiration(ctx, satellite, pieceID)
	}
	if store.v0PieceInfo != nil {
		err = errs.Combine(err, store.v0PieceInfo.Delete(ctx, satellite, pieceID))
	}

	return Error.Wrap(err)
}

// Trash moves the specified piece to the blob trash. If necessary, it converts
// the v0 piece to a v1 piece. It also marks the item as "trashed" in the
// pieceExpirationDB.
func (store *Store) Trash(ctx context.Context, satellite storj.NodeID, pieceID storj.PieceID) (err error) {
	defer mon.Task()(&ctx)(&err)

	// Check if the MaxFormatVersionSupported piece exists. If not, we assume
	// this is an old piece version and attempt to migrate it.
	_, err = store.blobs.StatWithStorageFormat(ctx, storage.BlobRef{
		Namespace: satellite.Bytes(),
		Key:       pieceID.Bytes(),
	}, filestore.MaxFormatVersionSupported)
	if err != nil && !errs.IsFunc(err, os.IsNotExist) {
		return Error.Wrap(err)
	}

	if errs.IsFunc(err, os.IsNotExist) {
		// MaxFormatVersionSupported does not exist, migrate.
		err = store.MigrateV0ToV1(ctx, satellite, pieceID)
		if err != nil {
			return Error.Wrap(err)
		}
	}

	err = store.expirationInfo.Trash(ctx, satellite, pieceID)
	err = errs.Combine(err, store.blobs.Trash(ctx, storage.BlobRef{
		Namespace: satellite.Bytes(),
		Key:       pieceID.Bytes(),
	}))

	return Error.Wrap(err)
}

// EmptyTrash deletes pieces in the trash that have been in there longer than trashExpiryInterval
func (store *Store) EmptyTrash(ctx context.Context, satelliteID storj.NodeID, trashedBefore time.Time) (err error) {
	defer mon.Task()(&ctx)(&err)

	deletedIDs, err := store.blobs.EmptyTrash(ctx, satelliteID[:], trashedBefore)
	if err != nil {
		return Error.Wrap(err)
	}

	for _, deletedID := range deletedIDs {
		pieceID, pieceIDErr := storj.PieceIDFromBytes(deletedID)
		if pieceIDErr != nil {
			return Error.Wrap(pieceIDErr)
		}
		_, deleteErr := store.expirationInfo.DeleteExpiration(ctx, satelliteID, pieceID)
		err = errs.Combine(err, deleteErr)
	}
	return Error.Wrap(err)
}

// RestoreTrash restores all pieces in the trash
func (store *Store) RestoreTrash(ctx context.Context, satelliteID storj.NodeID) (err error) {
	defer mon.Task()(&ctx)(&err)

	err = store.blobs.RestoreTrash(ctx, satelliteID.Bytes())
	if err != nil {
		return Error.Wrap(err)
	}
	return Error.Wrap(store.expirationInfo.RestoreTrash(ctx, satelliteID))
}

// MigrateV0ToV1 will migrate a piece stored with storage format v0 to storage
// format v1. If the piece is not stored as a v0 piece it will return an error.
// The follow failures are possible:
// - Fail to open or read v0 piece. In this case no artifacts remain.
// - Fail to Write or Commit v1 piece. In this case no artifacts remain.
// - Fail to Delete v0 piece. In this case v0 piece may remain, but v1 piece
//   will exist and be preferred in future calls.
func (store *Store) MigrateV0ToV1(ctx context.Context, satelliteID storj.NodeID, pieceID storj.PieceID) (err error) {
	defer mon.Task()(&ctx)(&err)

	info, err := store.v0PieceInfo.Get(ctx, satelliteID, pieceID)
	if err != nil {
		return Error.Wrap(err)
	}

	err = func() (err error) {
		r, err := store.Reader(ctx, satelliteID, pieceID)
		if err != nil {
			return err
		}
		defer func() { err = errs.Combine(err, r.Close()) }()

		w, err := store.Writer(ctx, satelliteID, pieceID)
		if err != nil {
			return err
		}

		_, err = io.Copy(w, r)
		if err != nil {
			return errs.Combine(err, w.Cancel(ctx))
		}

		header := &pb.PieceHeader{
			Hash:         w.Hash(),
			CreationTime: info.PieceCreation,
			Signature:    info.UplinkPieceHash.GetSignature(),
			OrderLimit:   *info.OrderLimit,
		}

		return w.Commit(ctx, header)
	}()
	if err != nil {
		return Error.Wrap(err)
	}

	err = store.blobs.DeleteWithStorageFormat(ctx, storage.BlobRef{
		Namespace: satelliteID.Bytes(),
		Key:       pieceID.Bytes(),
	}, filestore.FormatV0)

	if store.v0PieceInfo != nil {
		err = errs.Combine(err, store.v0PieceInfo.Delete(ctx, satelliteID, pieceID))
	}

	return Error.Wrap(err)
}

// GetV0PieceInfoDBForTest returns this piece-store's reference to the V0 piece info DB (or nil,
// if this piece-store does not have one). This is ONLY intended for use with testing
// functionality.
func (store StoreForTest) GetV0PieceInfoDBForTest() V0PieceInfoDBForTest {
	if store.v0PieceInfo == nil {
		return nil
	}
	return store.v0PieceInfo.(V0PieceInfoDBForTest)
}

// GetHashAndLimit returns the PieceHash and OrderLimit associated with the specified piece. The
// piece must already have been opened for reading, and the associated *Reader passed in.
//
// Once we have migrated everything off of V0 storage and no longer need to support it, this can
// cleanly become a method directly on *Reader and will need only the 'pieceID' parameter.
func (store *Store) GetHashAndLimit(ctx context.Context, satellite storj.NodeID, pieceID storj.PieceID, reader *Reader) (pb.PieceHash, pb.OrderLimit, error) {
	if reader.StorageFormatVersion() == filestore.FormatV0 {
		info, err := store.GetV0PieceInfo(ctx, satellite, pieceID)
		if err != nil {
			return pb.PieceHash{}, pb.OrderLimit{}, err // err is already wrapped as a storagenodedb.ErrPieceInfo
		}
		return *info.UplinkPieceHash, *info.OrderLimit, nil
	}
	header, err := reader.GetPieceHeader()
	if err != nil {
		return pb.PieceHash{}, pb.OrderLimit{}, Error.Wrap(err)
	}
	pieceHash := pb.PieceHash{
		PieceId:   pieceID,
		Hash:      header.GetHash(),
		PieceSize: reader.Size(),
		Timestamp: header.GetCreationTime(),
		Signature: header.GetSignature(),
	}
	return pieceHash, header.OrderLimit, nil
}

// WalkSatellitePieces executes walkFunc for each locally stored piece in the namespace of the
// given satellite. If walkFunc returns a non-nil error, WalkSatellitePieces will stop iterating
// and return the error immediately. The ctx parameter is intended specifically to allow canceling
// iteration early.
//
// Note that this method includes all locally stored pieces, both V0 and higher.
func (store *Store) WalkSatellitePieces(ctx context.Context, satellite storj.NodeID, walkFunc func(StoredPieceAccess) error) (err error) {
	defer mon.Task()(&ctx)(&err)
	// first iterate over all in V1 storage, then all in V0
	err = store.blobs.WalkNamespace(ctx, satellite.Bytes(), func(blobInfo storage.BlobInfo) error {
		if blobInfo.StorageFormatVersion() < filestore.FormatV1 {
			// we'll address this piece while iterating over the V0 pieces below.
			return nil
		}
		pieceAccess, err := newStoredPieceAccess(store, blobInfo)
		if err != nil {
			// this is not a real piece blob. the blob store can't distinguish between actual piece
			// blobs and stray files whose names happen to decode as valid base32. skip this
			// "blob".
			return nil
		}
		return walkFunc(pieceAccess)
	})
	if err == nil && store.v0PieceInfo != nil {
		err = store.v0PieceInfo.WalkSatelliteV0Pieces(ctx, store.blobs, satellite, walkFunc)
	}
	return err
}

// GetExpired gets piece IDs that are expired and were created before the given time
func (store *Store) GetExpired(ctx context.Context, expiredAt time.Time, limit int64) (_ []ExpiredInfo, err error) {
	defer mon.Task()(&ctx)(&err)

	expired, err := store.expirationInfo.GetExpired(ctx, expiredAt, limit)
	if err != nil {
		return nil, err
	}
	if int64(len(expired)) < limit && store.v0PieceInfo != nil {
		v0Expired, err := store.v0PieceInfo.GetExpired(ctx, expiredAt, limit-int64(len(expired)))
		if err != nil {
			return nil, err
		}
		expired = append(expired, v0Expired...)
	}
	return expired, nil
}

// SetExpiration records an expiration time for the specified piece ID owned by the specified satellite
func (store *Store) SetExpiration(ctx context.Context, satellite storj.NodeID, pieceID storj.PieceID, expiresAt time.Time) (err error) {
	return store.expirationInfo.SetExpiration(ctx, satellite, pieceID, expiresAt)
}

// DeleteFailed marks piece as a failed deletion.
func (store *Store) DeleteFailed(ctx context.Context, expired ExpiredInfo, when time.Time) (err error) {
	defer mon.Task()(&ctx)(&err)

	if expired.InPieceInfo {
		return store.v0PieceInfo.DeleteFailed(ctx, expired.SatelliteID, expired.PieceID, when)
	}
	return store.expirationInfo.DeleteFailed(ctx, expired.SatelliteID, expired.PieceID, when)
}

// SpaceUsedForPieces returns *an approximation of* the disk space used by all local pieces (both
// V0 and later). This is an approximation because changes may be being applied to the filestore as
// this information is collected, and because it is possible that various errors in directory
// traversal could cause this count to be undersized.
//
// Important note: this metric does not include space used by piece headers, whereas
// storj/filestore/store.(*Store).SpaceUsed() *does* include all space used by the blobs.
func (store *Store) SpaceUsedForPieces(ctx context.Context) (int64, error) {
	if cache, ok := store.blobs.(*BlobsUsageCache); ok {
		return cache.SpaceUsedForPieces(ctx)
	}
	satellites, err := store.getAllStoringSatellites(ctx)
	if err != nil {
		return 0, err
	}
	var total int64
	for _, satellite := range satellites {
		spaceUsed, err := store.SpaceUsedBySatellite(ctx, satellite)
		if err != nil {
			return 0, err
		}
		total += spaceUsed
	}
	return total, nil
}

func (store *Store) getAllStoringSatellites(ctx context.Context) ([]storj.NodeID, error) {
	namespaces, err := store.blobs.ListNamespaces(ctx)
	if err != nil {
		return nil, err
	}
	satellites := make([]storj.NodeID, len(namespaces))
	for i, namespace := range namespaces {
		satellites[i], err = storj.NodeIDFromBytes(namespace)
		if err != nil {
			return nil, err
		}
	}
	return satellites, nil
}

// SpaceUsedBySatellite calculates *an approximation of* how much disk space is used for local
// piece storage in the given satellite's namespace. This is an approximation because changes may
// be being applied to the filestore as this information is collected, and because it is possible
// that various errors in directory traversal could cause this count to be undersized.
//
// Important note: this metric does not include space used by piece headers, whereas
// storj/filestore/store.(*Store).SpaceUsedInNamespace() *does* include all space used by the
// blobs.
func (store *Store) SpaceUsedBySatellite(ctx context.Context, satelliteID storj.NodeID) (int64, error) {
	if cache, ok := store.blobs.(*BlobsUsageCache); ok {
		return cache.SpaceUsedBySatellite(ctx, satelliteID)
	}

	var totalUsed int64
	err := store.WalkSatellitePieces(ctx, satelliteID, func(access StoredPieceAccess) error {
		contentSize, statErr := access.ContentSize(ctx)
		if statErr != nil {
			store.log.Error("failed to stat", zap.Error(statErr), zap.Stringer("Piece ID", access.PieceID()), zap.Stringer("Satellite ID", satelliteID))
			// keep iterating; we want a best effort total here.
			return nil
		}
		totalUsed += contentSize
		return nil
	})
	if err != nil {
		return 0, err
	}
	return totalUsed, nil
}

// SpaceUsedTotalAndBySatellite adds up the space used by and for all satellites for blob storage
func (store *Store) SpaceUsedTotalAndBySatellite(ctx context.Context) (total int64, totalBySatellite map[storj.NodeID]int64, err error) {
	defer mon.Task()(&ctx)(&err)

	satelliteIDs, err := store.getAllStoringSatellites(ctx)
	if err != nil {
		return total, totalBySatellite, Error.New("failed to enumerate satellites: %v", err)
	}

	totalBySatellite = map[storj.NodeID]int64{}
	for _, satelliteID := range satelliteIDs {
		var totalUsed int64

		err := store.WalkSatellitePieces(ctx, satelliteID, func(access StoredPieceAccess) error {
			contentSize, err := access.ContentSize(ctx)
			if err != nil {
				return err
			}
			totalUsed += contentSize
			return nil
		})
		if err != nil {
			return total, totalBySatellite, err
		}

		total += totalUsed
		totalBySatellite[satelliteID] = totalUsed
	}
	return total, totalBySatellite, nil
}

// GetV0PieceInfo fetches the Info record from the V0 piece info database. Obviously,
// of no use when a piece does not have filestore.FormatV0 storage.
func (store *Store) GetV0PieceInfo(ctx context.Context, satellite storj.NodeID, pieceID storj.PieceID) (*Info, error) {
	return store.v0PieceInfo.Get(ctx, satellite, pieceID)
}

// StorageStatus contains information about the disk store is using.
type StorageStatus struct {
	DiskUsed int64
	DiskFree int64
}

// StorageStatus returns information about the disk.
func (store *Store) StorageStatus(ctx context.Context) (_ StorageStatus, err error) {
	defer mon.Task()(&ctx)(&err)
	diskFree, err := store.blobs.FreeSpace()
	if err != nil {
		return StorageStatus{}, err
	}
	return StorageStatus{
		DiskUsed: -1, // TODO set value
		DiskFree: diskFree,
	}, nil
}

type storedPieceAccess struct {
	storage.BlobInfo
	store   *Store
	pieceID storj.PieceID
}

func newStoredPieceAccess(store *Store, blobInfo storage.BlobInfo) (storedPieceAccess, error) {
	pieceID, err := storj.PieceIDFromBytes(blobInfo.BlobRef().Key)
	if err != nil {
		return storedPieceAccess{}, err
	}
	return storedPieceAccess{
		BlobInfo: blobInfo,
		store:    store,
		pieceID:  pieceID,
	}, nil
}

// PieceID returns the piece ID of the piece
func (access storedPieceAccess) PieceID() storj.PieceID {
	return access.pieceID
}

// Satellite returns the satellite ID that owns the piece
func (access storedPieceAccess) Satellite() (storj.NodeID, error) {
	return storj.NodeIDFromBytes(access.BlobRef().Namespace)
}

// ContentSize gives the size of the piece content (not including the piece header, if applicable)
func (access storedPieceAccess) ContentSize(ctx context.Context) (size int64, err error) {
	defer mon.Task()(&ctx)(&err)
	stat, err := access.Stat(ctx)
	if err != nil {
		return 0, err
	}
	size = stat.Size()
	if access.StorageFormatVersion() >= filestore.FormatV1 {
		size -= V1PieceHeaderReservedArea
	}
	return size, nil
}

// CreationTime returns the piece creation time as given in the original PieceHash (which is likely
// not the same as the file mtime). This requires opening the file and unmarshaling the piece
// header. If exact precision is not required, ModTime() may be a better solution.
func (access storedPieceAccess) CreationTime(ctx context.Context) (cTime time.Time, err error) {
	defer mon.Task()(&ctx)(&err)
	satellite, err := access.Satellite()
	if err != nil {
		return time.Time{}, err
	}
	reader, err := access.store.ReaderWithStorageFormat(ctx, satellite, access.PieceID(), access.StorageFormatVersion())
	if err != nil {
		return time.Time{}, err
	}
	header, err := reader.GetPieceHeader()
	if err != nil {
		return time.Time{}, err
	}
	return header.CreationTime, nil
}

// ModTime returns a less-precise piece creation time than CreationTime, but is generally
// much faster. This gets the piece creation time from to the filesystem instead of the
// piece header.
func (access storedPieceAccess) ModTime(ctx context.Context) (mTime time.Time, err error) {
	defer mon.Task()(&ctx)(&err)
	stat, err := access.Stat(ctx)
	if err != nil {
		return time.Time{}, err
	}

	return stat.ModTime(), nil
}