kpod attach

Attach to a running container

Signed-off-by: baude <bbaude@redhat.com>

Closes: #95
Approved by: rhatdan

README.md

@@ -34,7 +34,7 @@ libpod is currently in active development.
 | Command                                              | Description                                                               | Demo|
 | ---------------------------------------------------- | --------------------------------------------------------------------------|-----|
 | [kpod(1)](/docs/kpod.1.md)                           | Simple management tool for pods and images                                ||
-| [kpod-attach(1)](/docs/kpod-attach.1.md)             | Instead of providing a `kpod attach` command, the man page `kpod-attach` describes how to use the `kpod logs` and `kpod exec` commands to achieve the same goals as `kpod attach`.||
+| [kpod-attach(1)](/docs/kpod-attach.1.md)             | Attach to a running container.
 | [kpod-cp(1)](/docs/kpod-cp.1.md)                     | Instead of providing a `kpod cp` command, the man page `kpod-cp` describes how to use the `kpod mount` command to have even more flexibility and functionality.||
 | [kpod-diff(1)](/docs/kpod-diff.1.md)                 | Inspect changes on a container or image's filesystem                      |[![...](/docs/play.png)](https://asciinema.org/a/FXfWB9CKYFwYM4EfqW3NSZy1G)|
 | [kpod-export(1)](/docs/kpod-export.1.md)             | Export container's filesystem contents as a tar archive                   |[![...](/docs/play.png)](https://asciinema.org/a/913lBIRAg5hK8asyIhhkQVLtV)|

cmd/kpod/attach.go

@@ -0,0 +1,86 @@
+package main
+
+import (
+	"sync"
+
+	"github.com/pkg/errors"
+	"github.com/projectatomic/libpod/libpod"
+	"github.com/sirupsen/logrus"
+	"github.com/urfave/cli"
+)
+
+var (
+	attachFlags = []cli.Flag{
+		cli.StringFlag{
+			Name:  "detach-keys",
+			Usage: "Override the key sequence for detaching a container. Format is a single character [a-Z] or ctrl-<value> where <value> is one of: a-z, @, ^, [, , or _.",
+		},
+		cli.BoolFlag{
+			Name:  "no-stdin",
+			Usage: "Do not attach STDIN. The default is false.",
+		},
+	}
+	attachDescription = "The kpod attach command allows you to attach to a running container using the container's ID or name, either to view its ongoing output or to control it interactively."
+	attachCommand     = cli.Command{
+		Name:        "attach",
+		Usage:       "Attach to a running container",
+		Description: attachDescription,
+		Flags:       attachFlags,
+		Action:      attachCmd,
+		ArgsUsage:   "",
+	}
+)
+
+func attachCmd(c *cli.Context) error {
+	args := c.Args()
+	if err := validateFlags(c, attachFlags); err != nil {
+		return err
+	}
+
+	if len(c.Args()) < 1 || len(c.Args()) > 1 {
+		return errors.Errorf("attach requires the name or id of one running container")
+	}
+
+	runtime, err := getRuntime(c)
+	if err != nil {
+		return errors.Wrapf(err, "error creating libpod runtime")
+	}
+	defer runtime.Shutdown(false)
+
+	ctr, err := runtime.LookupContainer(args[0])
+
+	if err != nil {
+		return errors.Wrapf(err, "unable to exec into %s", args[0])
+	}
+
+	conState, err := ctr.State()
+	if err != nil {
+		return errors.Wrapf(err, "unable to determine state of %s", args[0])
+	}
+	if conState != libpod.ContainerStateRunning {
+		return errors.Errorf("you can only attach to running containers")
+	}
+	// Create a bool channel to track that the console socket attach
+	// is successful.
+	attached := make(chan bool)
+	// Create a waitgroup so we can sync and wait for all goroutines
+	// to finish before exiting main
+	var wg sync.WaitGroup
+
+	// We increment the wg counter because we need to do the attach
+	wg.Add(1)
+	// Attach to the running container
+	go func() {
+		logrus.Debug("trying to attach to the container %s", ctr.ID())
+		defer wg.Done()
+		if err := ctr.Attach(c.Bool("no-stdin"), c.String("detach-keys"), attached); err != nil {
+			logrus.Errorf("unable to attach to container %s: %q", ctr.ID(), err)
+		}
+	}()
+	if !<-attached {
+		return errors.Errorf("unable to attach to container %s", ctr.ID())
+	}
+	wg.Wait()
+
+	return nil
+}

cmd/kpod/main.go

@@ -34,6 +34,7 @@ func main() {
 	app.Version = v
 
 	app.Commands = []cli.Command{
+		attachCommand,
 		createCommand,
 		diffCommand,
 		exportCommand,

completions/bash/kpod

@@ -653,6 +653,17 @@ __kpod_images() {
 	__kpod_q images $images_args | awk "$awk_script" | grep -v '<none>$'
 }
 
+_kpod_attach() {
+     local options_with_args="
+     --detach-keys
+     "
+     local boolean_options="
+     --help
+     -h
+     --no-stdin"
+     _complete_ "$options_with_args" "$boolean_options"
+}
+
 _kpod_diff() {
     local options_with_args="
      --format
@@ -1443,6 +1454,7 @@ _kpod_kpod() {
            --version -v
      "
      commands="
+    attach
     create
     diff
     export

docs/kpod-attach.1.md

@@ -1,31 +1,40 @@
 % kpod(1) kpod-attach - See the output of pid 1 of a container or enter the container
 % Dan Walsh
-# kpod-attach "1" "September 2017" "kpod"
+# kpod-attach "1" "December 2017" "kpod"
 
 ## NAME
 kpod-attach - Attach to a running container
 
-## Description
+## SYNOPSIS
+**kpod attach [OPTIONS] CONTAINER**
 
-We chose not to implement the `attach` feature in `kpod` even though the upstream Docker
-project has it. The upstream project has had lots of issues with attaching to running
-processes that we did not want to replicate. The `kpod exec` and `kpod log` commands
-offer you the same functionality far more dependably.
+## DESCRIPTION
+The attach command allows you to attach to a running container using the container's ID
+or name, either to view its ongoing output or to control it interactively.
 
-**Reasons to attach to the primary PID of a container:**
+You can detach from the container (and leave it running) using a configurable key sequence. The default
+sequence is CTRL-p CTRL-q. You configure the key sequence using the --detach-keys option
 
+## OPTIONS
+**--detach-keys**
+Override the key sequence for detaching a container. Format is a single character [a-Z] or
+ctrl-<value> where <value> is one of: a-z, @, ^, [, , or _.
 
-1) Executing commands inside of the container
+**--no-stdin**
+Do not attach STDIN. The default is false.
 
-  We recommend that you use `kpod exec` to execute a command within a container
-
-  `kpod exec CONTAINERID /bin/sh`
-
-2) Viewing the output stream of the primary process in the container
-
-  We recommend that you use `kpod logs` to see the output from the container
-
-  `kpod logs CONTAINERID`
+## EXAMPLES ##
 
+```
+kpod attach foobar
+[root@localhost /]#
+```
+```
+kpod attach 1234
+[root@localhost /]#
+```
+```
+kpod attach --no-stdin foobar
+```
 ## SEE ALSO
-kpod(1), kpod-exec(1), kpod-logs(1)
+kpod(1), kpod-exec(1), kpod-run(1)

docs/kpod.1.md

@@ -52,6 +52,9 @@ has the capability to debug pods/images created by crio.
 
 ## COMMANDS
 
+### attach
+Attach to a running container
+
 ### create
 create a new container
 

test/kpod_attach.bats

@@ -0,0 +1,32 @@
+#!/usr/bin/env bats
+
+load helpers
+
+function teardown() {
+    cleanup_test
+}
+
+function setup() {
+    copy_images
+}
+
+@test "attach to a bogus container" {
+    run bash -c "${KPOD_BINARY} ${KPOD_OPTIONS} attach foobar"
+    echo "$output"
+    [ "$status" -eq 1 ]
+}
+
+@test "attach to non-running container" {
+    ${KPOD_BINARY} ${KPOD_OPTIONS} create --name foobar -d -i ${ALPINE} ls
+    run bash -c "${KPOD_BINARY} ${KPOD_OPTIONS} attach foobar"
+    echo "$output"
+    [ "$status" -eq 1 ]
+}
+
+@test "attach to multiple containers" {
+    ${KPOD_BINARY} ${KPOD_OPTIONS} run --name foobar1 -d -i ${ALPINE} /bin/sh
+    ${KPOD_BINARY} ${KPOD_OPTIONS} run --name foobar2 -d -i ${ALPINE} /bin/sh
+    run bash -c "${KPOD_BINARY} ${KPOD_OPTIONS} attach foobar1 foobar2"
+    echo "$output"
+    [ "$status" -eq 1 ]
+}