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communicator.go
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communicator.go
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package docker
import (
"archive/tar"
"bytes"
"fmt"
"io"
"io/ioutil"
"log"
"os"
"os/exec"
"path/filepath"
"strconv"
"sync"
"syscall"
"time"
"github.com/ActiveState/tail"
"github.com/hashicorp/go-version"
"github.com/mitchellh/packer/packer"
)
type Communicator struct {
ContainerId string
HostDir string
ContainerDir string
Version *version.Version
Config *Config
lock sync.Mutex
}
func (c *Communicator) Start(remote *packer.RemoteCmd) error {
// Create a temporary file to store the output. Because of a bug in
// Docker, sometimes all the output doesn't properly show up. This
// file will capture ALL of the output, and we'll read that.
//
// https://github.com/dotcloud/docker/issues/2625
outputFile, err := ioutil.TempFile(c.HostDir, "cmd")
if err != nil {
return err
}
outputFile.Close()
// This file will store the exit code of the command once it is complete.
exitCodePath := outputFile.Name() + "-exit"
var cmd *exec.Cmd
if c.canExec() {
if c.Config.Pty {
cmd = exec.Command("docker", "exec", "-i", "-t", c.ContainerId, "/bin/sh")
} else {
cmd = exec.Command("docker", "exec", "-i", c.ContainerId, "/bin/sh")
}
} else {
cmd = exec.Command("docker", "attach", c.ContainerId)
}
stdin_w, err := cmd.StdinPipe()
if err != nil {
// We have to do some cleanup since run was never called
os.Remove(outputFile.Name())
os.Remove(exitCodePath)
return err
}
// Run the actual command in a goroutine so that Start doesn't block
go c.run(cmd, remote, stdin_w, outputFile, exitCodePath)
return nil
}
func (c *Communicator) Upload(dst string, src io.Reader, fi *os.FileInfo) error {
// Create a temporary file to store the upload
tempfile, err := ioutil.TempFile(c.HostDir, "upload")
if err != nil {
return err
}
defer os.Remove(tempfile.Name())
// Copy the contents to the temporary file
_, err = io.Copy(tempfile, src)
tempfile.Close()
if err != nil {
return err
}
// Copy the file into place by copying the temporary file we put
// into the shared folder into the proper location in the container
cmd := &packer.RemoteCmd{
Command: fmt.Sprintf("command cp %s/%s %s", c.ContainerDir,
filepath.Base(tempfile.Name()), dst),
}
if err := c.Start(cmd); err != nil {
return err
}
// Wait for the copy to complete
cmd.Wait()
if cmd.ExitStatus != 0 {
return fmt.Errorf("Upload failed with non-zero exit status: %d", cmd.ExitStatus)
}
return nil
}
func (c *Communicator) UploadDir(dst string, src string, exclude []string) error {
// Create the temporary directory that will store the contents of "src"
// for copying into the container.
td, err := ioutil.TempDir(c.HostDir, "dirupload")
if err != nil {
return err
}
defer os.RemoveAll(td)
walkFn := func(path string, info os.FileInfo, err error) error {
if err != nil {
return err
}
relpath, err := filepath.Rel(src, path)
if err != nil {
return err
}
hostpath := filepath.Join(td, relpath)
// If it is a directory, just create it
if info.IsDir() {
return os.MkdirAll(hostpath, info.Mode())
}
if info.Mode()&os.ModeSymlink == os.ModeSymlink {
dest, err := os.Readlink(path)
if err != nil {
return err
}
return os.Symlink(dest, hostpath)
}
// It is a file, copy it over, including mode.
src, err := os.Open(path)
if err != nil {
return err
}
defer src.Close()
dst, err := os.Create(hostpath)
if err != nil {
return err
}
defer dst.Close()
if _, err := io.Copy(dst, src); err != nil {
return err
}
si, err := src.Stat()
if err != nil {
return err
}
return dst.Chmod(si.Mode())
}
// Copy the entire directory tree to the temporary directory
if err := filepath.Walk(src, walkFn); err != nil {
return err
}
// Determine the destination directory
containerSrc := filepath.Join(c.ContainerDir, filepath.Base(td))
containerDst := dst
if src[len(src)-1] != '/' {
containerDst = filepath.Join(dst, filepath.Base(src))
}
// Make the directory, then copy into it
cmd := &packer.RemoteCmd{
Command: fmt.Sprintf("set -e; mkdir -p %s; command cp -R %s/* %s",
containerDst, containerSrc, containerDst),
}
if err := c.Start(cmd); err != nil {
return err
}
// Wait for the copy to complete
cmd.Wait()
if cmd.ExitStatus != 0 {
return fmt.Errorf("Upload failed with non-zero exit status: %d", cmd.ExitStatus)
}
return nil
}
// Download pulls a file out of a container using `docker cp`. We have a source
// path and want to write to an io.Writer, not a file. We use - to make docker
// cp to write to stdout, and then copy the stream to our destination io.Writer.
func (c *Communicator) Download(src string, dst io.Writer) error {
log.Printf("Downloading file from container: %s:%s", c.ContainerId, src)
localCmd := exec.Command("docker", "cp", fmt.Sprintf("%s:%s", c.ContainerId, src), "-")
pipe, err := localCmd.StdoutPipe()
if err != nil {
return fmt.Errorf("Failed to open pipe: %s", err)
}
if err = localCmd.Start(); err != nil {
return fmt.Errorf("Failed to start download: %s", err)
}
// When you use - to send docker cp to stdout it is streamed as a tar; this
// enables it to work with directories. We don't actually support
// directories in Download() but we still need to handle the tar format.
archive := tar.NewReader(pipe)
_, err = archive.Next()
if err != nil {
return fmt.Errorf("Failed to read header from tar stream: %s", err)
}
numBytes, err := io.Copy(dst, archive)
if err != nil {
return fmt.Errorf("Failed to pipe download: %s", err)
}
log.Printf("Copied %d bytes for %s", numBytes, src)
if err = localCmd.Wait(); err != nil {
return fmt.Errorf("Failed to download '%s' from container: %s", src, err)
}
return nil
}
// canExec tells us whether `docker exec` is supported
func (c *Communicator) canExec() bool {
execConstraint, err := version.NewConstraint(">= 1.4.0")
if err != nil {
panic(err)
}
return execConstraint.Check(c.Version)
}
// Runs the given command and blocks until completion
func (c *Communicator) run(cmd *exec.Cmd, remote *packer.RemoteCmd, stdin_w io.WriteCloser, outputFile *os.File, exitCodePath string) {
// For Docker, remote communication must be serialized since it
// only supports single execution.
c.lock.Lock()
defer c.lock.Unlock()
// Clean up after ourselves by removing our temporary files
defer os.Remove(outputFile.Name())
defer os.Remove(exitCodePath)
// Tail the output file and send the data to the stdout listener
tail, err := tail.TailFile(outputFile.Name(), tail.Config{
Poll: true,
ReOpen: true,
Follow: true,
})
if err != nil {
log.Printf("Error tailing output file: %s", err)
remote.SetExited(254)
return
}
defer tail.Stop()
// Modify the remote command so that all the output of the commands
// go to a single file and so that the exit code is redirected to
// a single file. This lets us determine both when the command
// is truly complete (because the file will have data), what the
// exit status is (because Docker loses it because of the pty, not
// Docker's fault), and get the output (Docker bug).
remoteCmd := fmt.Sprintf("(%s) >%s 2>&1; echo $? >%s",
remote.Command,
filepath.Join(c.ContainerDir, filepath.Base(outputFile.Name())),
filepath.Join(c.ContainerDir, filepath.Base(exitCodePath)))
// Start the command
log.Printf("Executing in container %s: %#v", c.ContainerId, remoteCmd)
if err := cmd.Start(); err != nil {
log.Printf("Error executing: %s", err)
remote.SetExited(254)
return
}
go func() {
defer stdin_w.Close()
// This sleep needs to be here because of the issue linked to below.
// Basically, without it, Docker will hang on reading stdin forever,
// and won't see what we write, for some reason.
//
// https://github.com/dotcloud/docker/issues/2628
time.Sleep(2 * time.Second)
stdin_w.Write([]byte(remoteCmd + "\n"))
}()
// Start a goroutine to read all the lines out of the logs. These channels
// allow us to stop the go-routine and wait for it to be stopped.
stopTailCh := make(chan struct{})
doneCh := make(chan struct{})
go func() {
defer close(doneCh)
for {
select {
case <-tail.Dead():
return
case line := <-tail.Lines:
if remote.Stdout != nil {
remote.Stdout.Write([]byte(line.Text + "\n"))
} else {
log.Printf("Command stdout: %#v", line.Text)
}
case <-time.After(2 * time.Second):
// If we're done, then return. Otherwise, keep grabbing
// data. This gives us a chance to flush all the lines
// out of the tailed file.
select {
case <-stopTailCh:
return
default:
}
}
}
}()
var exitRaw []byte
var exitStatus int
var exitStatusRaw int64
err = cmd.Wait()
if exitErr, ok := err.(*exec.ExitError); ok {
exitStatus = 1
// There is no process-independent way to get the REAL
// exit status so we just try to go deeper.
if status, ok := exitErr.Sys().(syscall.WaitStatus); ok {
exitStatus = status.ExitStatus()
}
// Say that we ended, since if Docker itself failed, then
// the command must've not run, or so we assume
goto REMOTE_EXIT
}
// Wait for the exit code to appear in our file...
log.Println("Waiting for exit code to appear for remote command...")
for {
fi, err := os.Stat(exitCodePath)
if err == nil && fi.Size() > 0 {
break
}
time.Sleep(1 * time.Second)
}
// Read the exit code
exitRaw, err = ioutil.ReadFile(exitCodePath)
if err != nil {
log.Printf("Error executing: %s", err)
exitStatus = 254
goto REMOTE_EXIT
}
exitStatusRaw, err = strconv.ParseInt(string(bytes.TrimSpace(exitRaw)), 10, 0)
if err != nil {
log.Printf("Error executing: %s", err)
exitStatus = 254
goto REMOTE_EXIT
}
exitStatus = int(exitStatusRaw)
log.Printf("Executed command exit status: %d", exitStatus)
REMOTE_EXIT:
// Wait for the tail to finish
close(stopTailCh)
<-doneCh
// Set the exit status which triggers waiters
remote.SetExited(exitStatus)
}