distribution/storagedriver/ipc/client.go

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package ipc
import (
"bytes"
"encoding/json"
"fmt"
"io"
"io/ioutil"
"net"
"os"
"os/exec"
"syscall"
"github.com/docker/docker-registry/storagedriver"
"github.com/docker/libchan"
"github.com/docker/libchan/spdy"
)
// StorageDriverExecutablePrefix is the prefix which the IPC storage driver
// loader expects driver executables to begin with. For example, the s3 driver
// should be named "registry-storagedriver-s3".
const StorageDriverExecutablePrefix = "registry-storagedriver-"
// StorageDriverClient is a storagedriver.StorageDriver implementation using a
// managed child process communicating over IPC using libchan with a unix domain
// socket
type StorageDriverClient struct {
subprocess *exec.Cmd
exitChan chan error
exitErr error
stopChan chan struct{}
socket *os.File
transport *spdy.Transport
sender libchan.Sender
version storagedriver.Version
}
// NewDriverClient constructs a new out-of-process storage driver using the
// driver name and configuration parameters
// A user must call Start on this driver client before remote method calls can
// be made
//
// Looks for drivers in the following locations in order:
// - Storage drivers directory (to be determined, yet not implemented)
// - $GOPATH/bin
// - $PATH
func NewDriverClient(name string, parameters map[string]string) (*StorageDriverClient, error) {
paramsBytes, err := json.Marshal(parameters)
if err != nil {
return nil, err
}
driverExecName := StorageDriverExecutablePrefix + name
driverPath, err := exec.LookPath(driverExecName)
if err != nil {
return nil, err
}
command := exec.Command(driverPath, string(paramsBytes))
return &StorageDriverClient{
subprocess: command,
}, nil
}
// Start starts the designated child process storage driver and binds a socket
// to this process for IPC method calls
func (driver *StorageDriverClient) Start() error {
driver.exitErr = nil
driver.exitChan = make(chan error)
driver.stopChan = make(chan struct{})
fileDescriptors, err := syscall.Socketpair(syscall.AF_LOCAL, syscall.SOCK_STREAM, 0)
if err != nil {
return err
}
childSocket := os.NewFile(uintptr(fileDescriptors[0]), "childSocket")
driver.socket = os.NewFile(uintptr(fileDescriptors[1]), "parentSocket")
driver.subprocess.Stdout = os.Stdout
driver.subprocess.Stderr = os.Stderr
driver.subprocess.ExtraFiles = []*os.File{childSocket}
if err = driver.subprocess.Start(); err != nil {
driver.Stop()
return err
}
go driver.handleSubprocessExit()
if err = childSocket.Close(); err != nil {
driver.Stop()
return err
}
connection, err := net.FileConn(driver.socket)
if err != nil {
driver.Stop()
return err
}
driver.transport, err = spdy.NewClientTransport(connection)
if err != nil {
driver.Stop()
return err
}
driver.sender, err = driver.transport.NewSendChannel()
if err != nil {
driver.Stop()
return err
}
// Check the driver's version to determine compatibility
receiver, remoteSender := libchan.Pipe()
err = driver.sender.Send(&Request{Type: "Version", ResponseChannel: remoteSender})
if err != nil {
driver.Stop()
return err
}
var response VersionResponse
err = receiver.Receive(&response)
if err != nil {
driver.Stop()
return err
}
if response.Error != nil {
return response.Error.Unwrap()
}
driver.version = response.Version
if driver.version.Major() != storagedriver.CurrentVersion.Major() || driver.version.Minor() > storagedriver.CurrentVersion.Minor() {
return IncompatibleVersionError{driver.version}
}
return nil
}
// Stop stops the child process storage driver
// storagedriver.StorageDriver methods called after Stop will fail
func (driver *StorageDriverClient) Stop() error {
var closeSenderErr, closeTransportErr, closeSocketErr, killErr error
if driver.sender != nil {
closeSenderErr = driver.sender.Close()
}
if driver.transport != nil {
closeTransportErr = driver.transport.Close()
}
if driver.socket != nil {
closeSocketErr = driver.socket.Close()
}
if driver.subprocess != nil {
killErr = driver.subprocess.Process.Kill()
}
if driver.stopChan != nil {
driver.stopChan <- struct{}{}
close(driver.stopChan)
}
if closeSenderErr != nil {
return closeSenderErr
} else if closeTransportErr != nil {
return closeTransportErr
} else if closeSocketErr != nil {
return closeSocketErr
}
return killErr
}
// Implement the storagedriver.StorageDriver interface over IPC
// GetContent retrieves the content stored at "path" as a []byte.
func (driver *StorageDriverClient) GetContent(path string) ([]byte, error) {
if err := driver.exited(); err != nil {
return nil, err
}
receiver, remoteSender := libchan.Pipe()
params := map[string]interface{}{"Path": path}
err := driver.sender.Send(&Request{Type: "GetContent", Parameters: params, ResponseChannel: remoteSender})
if err != nil {
return nil, err
}
response := new(ReadStreamResponse)
err = driver.receiveResponse(receiver, response)
if err != nil {
return nil, err
}
if response.Error != nil {
return nil, response.Error.Unwrap()
}
defer response.Reader.Close()
contents, err := ioutil.ReadAll(response.Reader)
if err != nil {
return nil, err
}
return contents, nil
}
// PutContent stores the []byte content at a location designated by "path".
func (driver *StorageDriverClient) PutContent(path string, contents []byte) error {
if err := driver.exited(); err != nil {
return err
}
receiver, remoteSender := libchan.Pipe()
params := map[string]interface{}{"Path": path, "Reader": ioutil.NopCloser(bytes.NewReader(contents))}
err := driver.sender.Send(&Request{Type: "PutContent", Parameters: params, ResponseChannel: remoteSender})
if err != nil {
return err
}
response := new(WriteStreamResponse)
err = driver.receiveResponse(receiver, response)
if err != nil {
return err
}
if response.Error != nil {
return response.Error.Unwrap()
}
return nil
}
// ReadStream retrieves an io.ReadCloser for the content stored at "path" with a
// given byte offset.
func (driver *StorageDriverClient) ReadStream(path string, offset uint64) (io.ReadCloser, error) {
if err := driver.exited(); err != nil {
return nil, err
}
receiver, remoteSender := libchan.Pipe()
params := map[string]interface{}{"Path": path, "Offset": offset}
err := driver.sender.Send(&Request{Type: "ReadStream", Parameters: params, ResponseChannel: remoteSender})
if err != nil {
return nil, err
}
response := new(ReadStreamResponse)
err = driver.receiveResponse(receiver, response)
if err != nil {
return nil, err
}
if response.Error != nil {
return nil, response.Error.Unwrap()
}
return response.Reader, nil
}
// WriteStream stores the contents of the provided io.ReadCloser at a location
// designated by the given path.
func (driver *StorageDriverClient) WriteStream(path string, offset, size uint64, reader io.ReadCloser) error {
if err := driver.exited(); err != nil {
return err
}
receiver, remoteSender := libchan.Pipe()
params := map[string]interface{}{"Path": path, "Offset": offset, "Size": size, "Reader": reader}
err := driver.sender.Send(&Request{Type: "WriteStream", Parameters: params, ResponseChannel: remoteSender})
if err != nil {
return err
}
response := new(WriteStreamResponse)
err = driver.receiveResponse(receiver, response)
if err != nil {
return err
}
if response.Error != nil {
return response.Error.Unwrap()
}
return nil
}
// CurrentSize retrieves the curernt size in bytes of the object at the given
// path.
func (driver *StorageDriverClient) CurrentSize(path string) (uint64, error) {
if err := driver.exited(); err != nil {
return 0, err
}
receiver, remoteSender := libchan.Pipe()
params := map[string]interface{}{"Path": path}
err := driver.sender.Send(&Request{Type: "CurrentSize", Parameters: params, ResponseChannel: remoteSender})
if err != nil {
return 0, err
}
response := new(CurrentSizeResponse)
err = driver.receiveResponse(receiver, response)
if err != nil {
return 0, err
}
if response.Error != nil {
return 0, response.Error.Unwrap()
}
return response.Position, nil
}
// List returns a list of the objects that are direct descendants of the given
// path.
func (driver *StorageDriverClient) List(path string) ([]string, error) {
if err := driver.exited(); err != nil {
return nil, err
}
receiver, remoteSender := libchan.Pipe()
params := map[string]interface{}{"Path": path}
err := driver.sender.Send(&Request{Type: "List", Parameters: params, ResponseChannel: remoteSender})
if err != nil {
return nil, err
}
response := new(ListResponse)
err = driver.receiveResponse(receiver, response)
if err != nil {
return nil, err
}
if response.Error != nil {
return nil, response.Error.Unwrap()
}
return response.Keys, nil
}
// Move moves an object stored at sourcePath to destPath, removing the original
// object.
func (driver *StorageDriverClient) Move(sourcePath string, destPath string) error {
if err := driver.exited(); err != nil {
return err
}
receiver, remoteSender := libchan.Pipe()
params := map[string]interface{}{"SourcePath": sourcePath, "DestPath": destPath}
err := driver.sender.Send(&Request{Type: "Move", Parameters: params, ResponseChannel: remoteSender})
if err != nil {
return err
}
response := new(MoveResponse)
err = driver.receiveResponse(receiver, response)
if err != nil {
return err
}
if response.Error != nil {
return response.Error.Unwrap()
}
return nil
}
// Delete recursively deletes all objects stored at "path" and its subpaths.
func (driver *StorageDriverClient) Delete(path string) error {
if err := driver.exited(); err != nil {
return err
}
receiver, remoteSender := libchan.Pipe()
params := map[string]interface{}{"Path": path}
err := driver.sender.Send(&Request{Type: "Delete", Parameters: params, ResponseChannel: remoteSender})
if err != nil {
return err
}
response := new(DeleteResponse)
err = driver.receiveResponse(receiver, response)
if err != nil {
return err
}
if response.Error != nil {
return response.Error.Unwrap()
}
return nil
}
// handleSubprocessExit populates the exit channel until we have explicitly
// stopped the storage driver subprocess
// Requests can select on driver.exitChan and response receiving and not hang if
// the process exits
func (driver *StorageDriverClient) handleSubprocessExit() {
exitErr := driver.subprocess.Wait()
if exitErr == nil {
exitErr = fmt.Errorf("Storage driver subprocess already exited cleanly")
} else {
exitErr = fmt.Errorf("Storage driver subprocess exited with error: %s", exitErr)
}
driver.exitErr = exitErr
for {
select {
case driver.exitChan <- exitErr:
case <-driver.stopChan:
close(driver.exitChan)
return
}
}
}
// receiveResponse populates the response value with the next result from the
// given receiver, or returns an error if receiving failed or the driver has
// stopped
func (driver *StorageDriverClient) receiveResponse(receiver libchan.Receiver, response interface{}) error {
receiveChan := make(chan error, 1)
go func(receiver libchan.Receiver, receiveChan chan<- error) {
receiveChan <- receiver.Receive(response)
}(receiver, receiveChan)
var err error
var ok bool
select {
case err = <-receiveChan:
case err, ok = <-driver.exitChan:
if !ok {
err = driver.exitErr
}
}
return err
}
// exited returns an exit error if the driver has exited or nil otherwise
func (driver *StorageDriverClient) exited() error {
select {
case err, ok := <-driver.exitChan:
if !ok {
return driver.exitErr
}
return err
default:
return nil
}
}