attach.go

/*
Copyright 2014 The Kubernetes Authors All rights reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package cmd

import (
	"fmt"
	"io"
	"net/url"

	"github.com/golang/glog"
	"github.com/spf13/cobra"

	"k8s.io/kubernetes/pkg/api"
	"k8s.io/kubernetes/pkg/client/restclient"
	client "k8s.io/kubernetes/pkg/client/unversioned"
	"k8s.io/kubernetes/pkg/client/unversioned/remotecommand"
	cmdutil "k8s.io/kubernetes/pkg/kubectl/cmd/util"
	remotecommandserver "k8s.io/kubernetes/pkg/kubelet/server/remotecommand"
	utilerrors "k8s.io/kubernetes/pkg/util/errors"
	"k8s.io/kubernetes/pkg/util/interrupt"
	"k8s.io/kubernetes/pkg/util/term"
)

const (
	attach_example = `# Get output from running pod 123456-7890, using the first container by default
kubectl attach 123456-7890

# Get output from ruby-container from pod 123456-7890
kubectl attach 123456-7890 -c ruby-container

# Switch to raw terminal mode, sends stdin to 'bash' in ruby-container from pod 123456-7890
# and sends stdout/stderr from 'bash' back to the client
kubectl attach 123456-7890 -c ruby-container -i -t`
)

func NewCmdAttach(f *cmdutil.Factory, cmdIn io.Reader, cmdOut, cmdErr io.Writer) *cobra.Command {
	options := &AttachOptions{
		In:  cmdIn,
		Out: cmdOut,
		Err: cmdErr,

		CommandName: "kubectl attach",

		Attach: &DefaultRemoteAttach{},
	}
	cmd := &cobra.Command{
		Use:     "attach POD -c CONTAINER",
		Short:   "Attach to a running container.",
		Long:    "Attach to a process that is already running inside an existing container.",
		Example: attach_example,
		Run: func(cmd *cobra.Command, args []string) {
			cmdutil.CheckErr(options.Complete(f, cmd, args))
			cmdutil.CheckErr(options.Validate())
			cmdutil.CheckErr(options.Run())
		},
	}
	// TODO support UID
	cmd.Flags().StringVarP(&options.ContainerName, "container", "c", "", "Container name. If omitted, the first container in the pod will be chosen")
	cmd.Flags().BoolVarP(&options.Stdin, "stdin", "i", false, "Pass stdin to the container")
	cmd.Flags().BoolVarP(&options.TTY, "tty", "t", false, "Stdin is a TTY")
	return cmd
}

// RemoteAttach defines the interface accepted by the Attach command - provided for test stubbing
type RemoteAttach interface {
	Attach(method string, url *url.URL, config *restclient.Config, stdin io.Reader, stdout, stderr io.Writer, tty bool) error
}

// DefaultRemoteAttach is the standard implementation of attaching
type DefaultRemoteAttach struct{}

func (*DefaultRemoteAttach) Attach(method string, url *url.URL, config *restclient.Config, stdin io.Reader, stdout, stderr io.Writer, tty bool) error {
	exec, err := remotecommand.NewExecutor(config, method, url)
	if err != nil {
		return err
	}
	return exec.Stream(remotecommandserver.SupportedStreamingProtocols, stdin, stdout, stderr, tty)
}

// AttachOptions declare the arguments accepted by the Exec command
type AttachOptions struct {
	Namespace     string
	PodName       string
	ContainerName string
	Stdin         bool
	TTY           bool
	CommandName   string

	// InterruptParent, if set, is used to handle interrupts while attached
	InterruptParent *interrupt.Handler

	In  io.Reader
	Out io.Writer
	Err io.Writer

	Pod *api.Pod

	Attach RemoteAttach
	Client *client.Client
	Config *restclient.Config
}

// Complete verifies command line arguments and loads data from the command environment
func (p *AttachOptions) Complete(f *cmdutil.Factory, cmd *cobra.Command, argsIn []string) error {
	if len(argsIn) == 0 {
		return cmdutil.UsageError(cmd, "POD is required for attach")
	}
	if len(argsIn) > 1 {
		return cmdutil.UsageError(cmd, fmt.Sprintf("expected a single argument: POD, saw %d: %s", len(argsIn), argsIn))
	}
	p.PodName = argsIn[0]

	namespace, _, err := f.DefaultNamespace()
	if err != nil {
		return err
	}
	p.Namespace = namespace

	config, err := f.ClientConfig()
	if err != nil {
		return err
	}
	p.Config = config

	client, err := f.Client()
	if err != nil {
		return err
	}
	p.Client = client

	return nil
}

// Validate checks that the provided attach options are specified.
func (p *AttachOptions) Validate() error {
	allErrs := []error{}
	if len(p.PodName) == 0 {
		allErrs = append(allErrs, fmt.Errorf("pod name must be specified"))
	}
	if p.Out == nil || p.Err == nil {
		allErrs = append(allErrs, fmt.Errorf("both output and error output must be provided"))
	}
	if p.Attach == nil || p.Client == nil || p.Config == nil {
		allErrs = append(allErrs, fmt.Errorf("client, client config, and attach must be provided"))
	}
	return utilerrors.NewAggregate(allErrs)
}

// Run executes a validated remote execution against a pod.
func (p *AttachOptions) Run() error {
	if p.Pod == nil {
		pod, err := p.Client.Pods(p.Namespace).Get(p.PodName)
		if err != nil {
			return err
		}
		if pod.Status.Phase != api.PodRunning {
			return fmt.Errorf("pod %s is not running and cannot be attached to; current phase is %s", p.PodName, pod.Status.Phase)
		}
		p.Pod = pod
		// TODO: convert this to a clean "wait" behavior
	}
	pod := p.Pod

	// ensure we can recover the terminal while attached
	t := term.TTY{Parent: p.InterruptParent}

	// check for TTY
	tty := p.TTY
	containerToAttach := p.GetContainer(pod)
	if tty && !containerToAttach.TTY {
		tty = false
		fmt.Fprintf(p.Err, "Unable to use a TTY - container %s did not allocate one\n", containerToAttach.Name)
	}
	if p.Stdin {
		t.In = p.In
		if tty && !t.IsTerminal() {
			tty = false
			fmt.Fprintln(p.Err, "Unable to use a TTY - input is not a terminal or the right kind of file")
		}
	}
	t.Raw = tty

	fn := func() error {
		if tty {
			fmt.Fprintln(p.Out, "\nHit enter for command prompt")
		}
		// TODO: consider abstracting into a client invocation or client helper
		req := p.Client.RESTClient.Post().
			Resource("pods").
			Name(pod.Name).
			Namespace(pod.Namespace).
			SubResource("attach")
		req.VersionedParams(&api.PodAttachOptions{
			Container: containerToAttach.Name,
			Stdin:     p.In != nil,
			Stdout:    p.Out != nil,
			Stderr:    p.Err != nil,
			TTY:       tty,
		}, api.ParameterCodec)

		return p.Attach.Attach("POST", req.URL(), p.Config, p.In, p.Out, p.Err, tty)
	}

	if err := t.Safe(fn); err != nil {
		return err
	}

	if p.Stdin && tty && pod.Spec.RestartPolicy == api.RestartPolicyAlways {
		fmt.Fprintf(p.Out, "Session ended, resume using '%s %s -c %s -i -t' command when the pod is running\n", p.CommandName, pod.Name, containerToAttach.Name)
	}
	return nil
}

// GetContainer returns the container to attach to, with a fallback.
func (p *AttachOptions) GetContainer(pod *api.Pod) api.Container {
	if len(p.ContainerName) > 0 {
		for _, container := range pod.Spec.Containers {
			if container.Name == p.ContainerName {
				return container
			}
		}
	}

	glog.V(4).Infof("defaulting container name to %s", pod.Spec.Containers[0].Name)
	return pod.Spec.Containers[0]
}

// GetContainerName returns the name of the container to attach to, with a fallback.
func (p *AttachOptions) GetContainerName(pod *api.Pod) string {
	return p.GetContainer(pod).Name
}