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stream.go
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stream.go
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package s3
import (
"bytes"
"encoding/hex"
"errors"
"fmt"
"io"
"time"
"github.com/treeverse/lakefs/pkg/logging"
v4 "github.com/aws/aws-sdk-go/aws/signer/v4"
)
const (
StreamingSha256 = "STREAMING-AWS4-HMAC-SHA256-PAYLOAD"
StreamingContentEncoding = "aws-chunked"
)
type StreamingReader struct {
Reader io.Reader
Size int64
StreamSigner *v4.StreamSigner
Time time.Time
ChunkSize int
ChunkTimeout time.Duration
currentChunk io.Reader
totalRead int64
eof bool
}
func chunkBoundary(signature []byte, length int) []byte {
return []byte(fmt.Sprintf("%x;chunk-signature=%s\r\n", length, hex.EncodeToString(signature)))
}
func isEOF(err error) bool {
return err == io.EOF || errors.Is(err, io.ErrUnexpectedEOF)
}
func (s *StreamingReader) GetLastChunk() []byte {
res := make([]byte, 0)
sig, _ := s.StreamSigner.GetSignature([]byte{}, []byte{}, s.Time)
lastBoundary := chunkBoundary(sig, 0)
res = append(res, lastBoundary...)
res = append(res, '\r', '\n') // additional \r\n after the last boundary
return res
}
// ReadAllWithTimeout is taken from io.ReadAtLeast and adapted to support a timeout and a minimum read size
func ReadAllWithTimeout(r io.Reader, buf []byte, timeout time.Duration, minSize int) (n int, err error) {
desired := len(buf)
lg := logging.Default().WithFields(logging.Fields{
"timeout": timeout,
"desired_size": desired,
})
start := time.Now()
timedOut := false
for n < desired && err == nil {
var nn int
nn, err = r.Read(buf[n:])
n += nn
if time.Since(start) > timeout && n >= minChunkSize {
timedOut = true
break
}
}
if n >= desired {
err = nil
} else if n > 0 && err == io.EOF {
err = io.ErrUnexpectedEOF
}
if err == nil && timedOut {
err = ErrReaderTimeout
lg.WithField("n", n).Warn("duration passed, reader timed out")
}
return
}
var ErrReaderTimeout = errors.New("reader timeout")
func (s *StreamingReader) readNextChunk() error {
buf := make([]byte, s.ChunkSize)
n, err := ReadAllWithTimeout(s.Reader, buf, s.ChunkTimeout, minChunkSize)
s.totalRead += int64(n)
buf = buf[:n]
if err != nil && !isEOF(err) && !errors.Is(err, ErrReaderTimeout) {
// actual error happened
return err
}
if n == 0 {
if s.currentChunk == nil {
s.currentChunk = bytes.NewBuffer(s.GetLastChunk())
}
return io.EOF
}
sig, sigErr := s.StreamSigner.GetSignature([]byte{}, buf, s.Time)
if sigErr != nil {
return sigErr
}
buf = append(buf, '\r', '\n') // additional \r\n after the content
boundary := chunkBoundary(sig, n)
if isEOF(err) || s.totalRead == s.Size {
// we're done with the upstream Reader, let's write one last chunk boundary.
buf = append(buf, s.GetLastChunk()...)
}
buf = append(boundary, buf...)
s.currentChunk = bytes.NewBuffer(buf)
if s.totalRead == s.Size {
err = io.EOF
}
if errors.Is(err, ErrReaderTimeout) {
return nil // a slow reader shouldn't fail.
}
return err
}
func (s *StreamingReader) Read(p []byte) (int, error) {
if s.eof {
return 0, io.EOF
}
var nerr error
var currentN int
if s.currentChunk == nil {
nerr = s.readNextChunk()
if nerr != nil && !isEOF(nerr) {
return currentN, nerr
}
}
for currentN < len(p) {
n, err := s.currentChunk.Read(p[currentN:])
currentN += n
if err != nil && !isEOF(err) {
return currentN, err
}
if isEOF(err) { // we drained the current chunk
if isEOF(nerr) { // no more chunks to read
s.eof = true
return currentN, io.EOF
}
// otherwise, we read the entire chunk, let's fill it back up (if n < size of p)
nerr = s.readNextChunk()
if nerr != nil && !isEOF(nerr) {
return currentN, nerr // something bad happened when reading the next chunk
}
}
}
return currentN, nil
}