Docker attach bug.

DockerRun.go

func DockerRun(c *docker.Client, imageName string) (io.ReadCloser, error) {
	log.Printf("Create container...")
	cont, err := c.CreateContainer(docker.CreateContainerOptions{
		Config: &docker.Config{
			Hostname:     "generateruntimecontext",
			AttachStdout: true,
			AttachStderr: true,
			Image:        imageName,
			Labels: map[string]string{
				"orchestrator": "hanoverd",
				"purpose":      "Generate build context for runtime container",
			},
		},
	})
	if err != nil {
		log.Printf("Create container... failed: %v", err)
		return nil, err
	}

	log.Printf("Start build context emitter")
	err = c.StartContainer(cont.ID, &docker.HostConfig{})
	if err != nil {
		log.Printf("Start container... failed: %v", err)
		return nil, err
	}

	r, w := io.Pipe()

	go func() {
		log.Printf("AttachToContainer")
		err := c.AttachToContainer(docker.AttachToContainerOptions{
			Container:    cont.ID,
			OutputStream: &WriteMonitor{w},
			ErrorStream:  os.Stderr,
			Logs:         true,
			Stdout:       true,
			Stderr:       true,
			Stream:       true,
		})
		log.Printf("~AttachToContainer")
		// io.Pipe hardwired to never return error here.
		_ = w.CloseWithError(err)
	}()

	removeContainer := func() {
		err := c.RemoveContainer(docker.RemoveContainerOptions{
			ID:            cont.ID,
			RemoveVolumes: true,
			Force:         true,
		})
		if err != nil {
			log.Printf("Error removing intermediate container: %v", err)
		}
	}

	log.Printf("DockerRun succeeded")
	return struct {
		io.Reader
		io.Closer
	}{
		Reader: r,
		Closer: CloseFunc(func() error {
			defer removeContainer()
			log.Printf("Wait")
			status, err := c.WaitContainer(cont.ID)
			if err != nil {
				return err
			}
			if status != 0 {
				return fmt.Errorf("non-zero exit status: %v", err)
			}
			return nil
		}),
	}, err
}

type WriteMonitor struct{ io.Writer }

func (w *WriteMonitor) Write(bs []byte) (int, error) {
	n, err := w.Writer.Write(bs)
	log.Printf("Write() (%v, %v)", n, err)
	return n, err
}

type CloseFunc func() error

func (fn CloseFunc) Close() error { return fn() }

Writes during failure

Nov 12 17:11:33 ip-10-1-170-104.eu-west-1.compute.internal hanoverd[5901]: 2015/11/12 17:11:33 Create container...
Nov 12 17:11:33 ip-10-1-170-104.eu-west-1.compute.internal hanoverd[5901]: 2015/11/12 17:11:33 Start build context emitter
Nov 12 17:11:33 ip-10-1-170-104.eu-west-1.compute.internal hanoverd[5901]: 2015/11/12 17:11:33 DockerRun succeeded
Nov 12 17:11:33 ip-10-1-170-104.eu-west-1.compute.internal hanoverd[5901]: 2015/11/12 17:11:33 Building...
Nov 12 17:11:33 ip-10-1-170-104.eu-west-1.compute.internal hanoverd[5901]: 2015/11/12 17:11:33 AttachToContainer
Nov 12 17:11:33 ip-10-1-170-104.eu-west-1.compute.internal hanoverd[5901]: 2015/11/12 17:11:33 Write() (1033, <nil>)
Nov 12 17:11:33 ip-10-1-170-104.eu-west-1.compute.internal hanoverd[5901]: 2015/11/12 17:11:33 Write() (1028, <nil>)
[many of these with different lengths]
Nov 12 17:11:33 ip-10-1-170-104.eu-west-1.compute.internal hanoverd[5901]: 2015/11/12 17:11:33 Write() (124, <nil>)
Nov 12 17:11:33 ip-10-1-170-104.eu-west-1.compute.internal hanoverd[5901]: 2015/11/12 17:11:33 Write() (55, <nil>)
[program hangs]

Writes during success

Nov 12 17:11:58 ip-10-1-170-104.eu-west-1.compute.internal hanoverd[5973]: 2015/11/12 17:11:58 Create container...
Nov 12 17:11:58 ip-10-1-170-104.eu-west-1.compute.internal hanoverd[5973]: 2015/11/12 17:11:58 Start build context emitter
Nov 12 17:11:58 ip-10-1-170-104.eu-west-1.compute.internal hanoverd[5973]: 2015/11/12 17:11:58 DockerRun succeeded
Nov 12 17:11:58 ip-10-1-170-104.eu-west-1.compute.internal hanoverd[5973]: 2015/11/12 17:11:58 Building...
Nov 12 17:11:58 ip-10-1-170-104.eu-west-1.compute.internal hanoverd[5973]: 2015/11/12 17:11:58 AttachToContainer
Nov 12 17:11:58 ip-10-1-170-104.eu-west-1.compute.internal hanoverd[5973]: 2015/11/12 17:11:58 Write() (32768, <nil>)
Nov 12 17:11:58 ip-10-1-170-104.eu-west-1.compute.internal hanoverd[5973]: 2015/11/12 17:11:58 Write() (32768, <nil>)
Nov 12 17:11:58 ip-10-1-170-104.eu-west-1.compute.internal hanoverd[5973]: 2015/11/12 17:11:58 Write() (32768, <nil>)
Nov 12 17:11:58 ip-10-1-170-104.eu-west-1.compute.internal hanoverd[5973]: 2015/11/12 17:11:58 Write() (32768, <nil>)
[snip many of these]
Nov 12 17:11:58 ip-10-1-170-104.eu-west-1.compute.internal hanoverd[5973]: 2015/11/12 17:11:58 Write() (32768, <nil>)
Nov 12 17:11:58 ip-10-1-170-104.eu-west-1.compute.internal hanoverd[5973]: 2015/11/12 17:11:58 Write() (32768, <nil>)
Nov 12 17:11:58 ip-10-1-170-104.eu-west-1.compute.internal hanoverd[5973]: 2015/11/12 17:11:58 Write() (32768, <nil>)
Nov 12 17:11:58 ip-10-1-170-104.eu-west-1.compute.internal hanoverd[5973]: 2015/11/12 17:11:58 Write() (6144, <nil>)
Nov 12 17:11:58 ip-10-1-170-104.eu-west-1.compute.internal hanoverd[5973]: 2015/11/12 17:11:58 ~AttachToContainer