README
¶
stream
The stream package contains an implementation of
v1.Layer
that supports streaming access, i.e. the layer contents are read once and not
buffered.
Usage
package main
import (
"os"
"github.com/google/go-containerregistry/pkg/name"
"github.com/google/go-containerregistry/pkg/v1/remote"
"github.com/google/go-containerregistry/pkg/v1/stream"
)
// upload the contents of stdin as a layer to a local registry
func main() {
repo, err := name.NewRepository("localhost:5000/stream")
if err != nil {
panic(err)
}
layer := stream.NewLayer(os.Stdin)
if err := remote.WriteLayer(repo, layer); err != nil {
panic(err)
}
}
Structure
This implements the layer portion of an image
upload. We launch a goroutine that
is responsible for hashing the uncompressed contents to compute the DiffID,
gzipping them to produce the Compressed contents, and hashing/counting the
bytes to produce the Digest/Size. This goroutine writes to an
io.PipeWriter, which blocks until Compressed reads the gzipped contents from
the corresponding io.PipeReader.
Caveats
This assumes that you have an uncompressed layer (i.e. a tarball) and would like
to compress it. Calling Uncompressed is always an error. Likewise, other
methods are invalid until the contents of Compressed have been completely
consumed and Closed.
Using a stream.Layer will likely not work without careful consideration. For
example, in the mutate package, we defer computing the manifest and config
file until they are actually called. This allows you to mutate.Append a
streaming layer to an image without accidentally consuming it. Similarly, in
remote.Write, if calling Digest on a layer fails, we attempt to upload the
layer anyway, understanding that we may be dealing with a stream.Layer whose
contents need to be uploaded before we can upload the config file.
Given the structure of how this is implemented, forgetting to
Close a stream.Layer will leak a goroutine.
Documentation
¶
Overview ¶
Package stream implements a single-pass streaming v1.Layer.
Index ¶
Constants ¶
This section is empty.
Variables ¶
var ( // ErrNotComputed is returned when the requested value is not yet // computed because the stream has not been consumed yet. ErrNotComputed = errors.New("value not computed until stream is consumed") // ErrConsumed is returned by Compressed when the underlying stream has // already been consumed and closed. ErrConsumed = errors.New("stream was already consumed") )
Functions ¶
This section is empty.
Types ¶
type Layer ¶
type Layer struct {
// contains filtered or unexported fields
}
Layer is a streaming implementation of v1.Layer.
func NewLayer ¶
func NewLayer(rc io.ReadCloser, opts ...LayerOption) *Layer
NewLayer creates a Layer from an io.ReadCloser.
func (*Layer) Compressed ¶
func (l *Layer) Compressed() (io.ReadCloser, error)
Compressed implements v1.Layer.
func (*Layer) Uncompressed ¶
func (l *Layer) Uncompressed() (io.ReadCloser, error)
Uncompressed implements v1.Layer.
type LayerOption ¶
type LayerOption func(*Layer)
LayerOption applies options to layer
func WithCompressionLevel ¶
func WithCompressionLevel(level int) LayerOption
WithCompressionLevel sets the gzip compression. See `gzip.NewWriterLevel` for possible values.
func WithMediaType ¶
func WithMediaType(mt types.MediaType) LayerOption
WithMediaType is a functional option for overriding the layer's media type.
Source Files