storj/uplink/piecestore/download.go

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// Copyright (C) 2019 Storj Labs, Inc.
// See LICENSE for copying information.
package piecestore
import (
"context"
"io"
"github.com/zeebo/errs"
"storj.io/storj/pkg/auth/signing"
"storj.io/storj/pkg/identity"
"storj.io/storj/pkg/pb"
)
// Downloader is interface that can be used for downloading content.
// It matches signature of `io.ReadCloser`.
type Downloader interface {
Read([]byte) (int, error)
Close() error
}
// Download implements downloading from a piecestore.
type Download struct {
client *Client
limit *pb.OrderLimit2
peer *identity.PeerIdentity
stream pb.Piecestore_DownloadClient
read int64 // how much data we have read so far
allocated int64 // how far have we sent orders
downloaded int64 // how much data have we downloaded
downloadSize int64 // how much do we want to download
// what is the step we consider to upload
allocationStep int64
unread ReadBuffer
}
// Download starts a new download using the specified order limit at the specified offset and size.
func (client *Client) Download(ctx context.Context, limit *pb.OrderLimit2, offset, size int64) (Downloader, error) {
stream, err := client.client.Download(ctx)
if err != nil {
return nil, err
}
peer, err := identity.PeerIdentityFromContext(stream.Context())
if err != nil {
closeErr := stream.CloseSend()
_, recvErr := stream.Recv()
return nil, ErrInternal.Wrap(errs.Combine(err, ignoreEOF(closeErr), ignoreEOF(recvErr)))
}
err = stream.Send(&pb.PieceDownloadRequest{
Limit: limit,
Chunk: &pb.PieceDownloadRequest_Chunk{
Offset: offset,
ChunkSize: size,
},
})
if err != nil {
_, recvErr := stream.Recv()
return nil, ErrProtocol.Wrap(errs.Combine(err, recvErr))
}
download := &Download{
client: client,
limit: limit,
peer: peer,
stream: stream,
read: 0,
allocated: 0,
downloaded: 0,
downloadSize: size,
allocationStep: client.config.InitialStep,
}
if client.config.DownloadBufferSize <= 0 {
return &LockingDownload{download: download}, nil
}
return &LockingDownload{
download: NewBufferedDownload(download, int(client.config.DownloadBufferSize)),
}, nil
}
// Read downloads data from the storage node allocating as necessary.
func (client *Download) Read(data []byte) (read int, _ error) {
for client.read < client.downloadSize {
// read from buffer
n, err := client.unread.Read(data)
client.read += int64(n)
read += n
// if we have an error or are pending for an error, avoid further communication
// however we should still finish reading the unread data.
if err != nil || client.unread.Errored() {
return read, err
}
// do we need to send a new order to storagenode
if client.allocated-client.downloaded < client.allocationStep {
newAllocation := client.allocationStep
// have we downloaded more than we have allocated due to a generous storagenode?
if client.allocated-client.downloaded < 0 {
newAllocation += client.downloaded - client.allocated
}
// ensure we don't allocate more than we intend to read
if client.allocated+newAllocation > client.downloadSize {
newAllocation = client.downloadSize - client.allocated
}
// send an order
if newAllocation > 0 {
// sign the order
order, err := signing.SignOrder(client.client.signer, &pb.Order2{
SerialNumber: client.limit.SerialNumber,
Amount: newAllocation,
})
// something went wrong with signing
if err != nil {
client.unread.IncludeError(err)
return read, nil
}
err = client.stream.Send(&pb.PieceDownloadRequest{
Order: order,
})
if err != nil {
// other side doesn't want to talk to us anymore,
// or network went down
client.unread.IncludeError(err)
return read, nil
}
// update our allocation step
client.allocationStep = client.client.nextAllocationStep(client.allocationStep)
}
} // if end allocation sending
// we have data, no need to wait for a chunk
if read > 0 {
return read, nil
}
// we don't have data, wait for a chunk from storage node
response, err := client.stream.Recv()
if response != nil && response.Chunk != nil {
client.downloaded += int64(len(response.Chunk.Data))
client.unread.Fill(response.Chunk.Data)
}
// we still need to continue until we have actually handled all of the errors
client.unread.IncludeError(err)
}
// all downloaded
if read == 0 {
return 0, io.EOF
}
return read, nil
}
// Close closes the downloading.
func (client *Download) Close() error {
alldone := client.read == client.downloadSize
// close our sending end
closeErr := client.stream.CloseSend()
// try to read any pending error message
_, recvErr := client.stream.Recv()
if alldone {
// if we are all done, then we expecte io.EOF, but don't care about them
return Error.Wrap(errs.Combine(ignoreEOF(closeErr), ignoreEOF(recvErr)))
}
if client.unread.Errored() {
// something went wrong and we didn't manage to download all the content
return Error.Wrap(errs.Combine(client.unread.Error(), closeErr, recvErr))
}
// we probably closed download early, so we can ignore io.EOF-s
return Error.Wrap(errs.Combine(ignoreEOF(closeErr), ignoreEOF(recvErr)))
}
// ReadBuffer implements buffered reading with an error.
type ReadBuffer struct {
data []byte
err error
}
// Error returns an error if it was encountered.
func (buffer *ReadBuffer) Error() error { return buffer.err }
// Errored returns whether the buffer contains an error.
func (buffer *ReadBuffer) Errored() bool { return buffer.err != nil }
// Empty checks whether buffer needs to be filled.
func (buffer *ReadBuffer) Empty() bool {
return len(buffer.data) == 0 && buffer.err == nil
}
// IncludeError adds error at the end of the buffer.
func (buffer *ReadBuffer) IncludeError(err error) {
buffer.err = errs.Combine(buffer.err, err)
}
// Fill fills the buffer with the specified bytes.
func (buffer *ReadBuffer) Fill(data []byte) {
buffer.data = data
}
// Read reads from the buffer.
func (buffer *ReadBuffer) Read(data []byte) (n int, err error) {
if len(buffer.data) > 0 {
n = copy(data, buffer.data)
buffer.data = buffer.data[n:]
return n, nil
}
if buffer.err != nil {
return 0, buffer.err
}
return 0, nil
}