Remove dep on larger packages

This removes most of the deps on the larger packages for the shim and
reduces the binary size and memory footprint from a 7.1mb binary to a
2.6mb binary.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

Makefile

@@ -50,7 +50,7 @@ daemon-static:
 	cd containerd && go build -ldflags "-w -extldflags -static ${LDFLAGS}" -tags "$(BUILDTAGS)" -o ../bin/containerd
 
 shim: bin
-	cd containerd-shim && go build -tags "$(BUILDTAGS)" -o ../bin/containerd-shim
+	cd containerd-shim && go build -tags "$(BUILDTAGS)" -ldflags "-w" -o ../bin/containerd-shim
 
 shim-static:
 	cd containerd-shim && go build -ldflags "-w -extldflags -static ${LDFLAGS}" -tags "$(BUILDTAGS)" -o ../bin/containerd-shim

containerd-shim/console.go

@@ -0,0 +1,54 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"syscall"
+	"unsafe"
+)
+
+// NewConsole returns an initalized console that can be used within a container by copying bytes
+// from the master side to the slave that is attached as the tty for the container's init process.
+func newConsole(uid, gid int) (*os.File, string, error) {
+	master, err := os.OpenFile("/dev/ptmx", syscall.O_RDWR|syscall.O_NOCTTY|syscall.O_CLOEXEC, 0)
+	if err != nil {
+		return nil, "", err
+	}
+	console, err := ptsname(master)
+	if err != nil {
+		return nil, "", err
+	}
+	if err := unlockpt(master); err != nil {
+		return nil, "", err
+	}
+	if err := os.Chmod(console, 0600); err != nil {
+		return nil, "", err
+	}
+	if err := os.Chown(console, uid, gid); err != nil {
+		return nil, "", err
+	}
+	return master, console, nil
+}
+
+func ioctl(fd uintptr, flag, data uintptr) error {
+	if _, _, err := syscall.Syscall(syscall.SYS_IOCTL, fd, flag, data); err != 0 {
+		return err
+	}
+	return nil
+}
+
+// unlockpt unlocks the slave pseudoterminal device corresponding to the master pseudoterminal referred to by f.
+// unlockpt should be called before opening the slave side of a pty.
+func unlockpt(f *os.File) error {
+	var u int32
+	return ioctl(f.Fd(), syscall.TIOCSPTLCK, uintptr(unsafe.Pointer(&u)))
+}
+
+// ptsname retrieves the name of the first available pts for the given master.
+func ptsname(f *os.File) (string, error) {
+	var n int32
+	if err := ioctl(f.Fd(), syscall.TIOCGPTN, uintptr(unsafe.Pointer(&n))); err != nil {
+		return "", err
+	}
+	return fmt.Sprintf("/dev/pts/%d", n), nil
+}

containerd-shim/main.go

@@ -8,11 +8,14 @@ import (
 	"path/filepath"
 	"syscall"
 
-	"github.com/Sirupsen/logrus"
 	"github.com/docker/containerd/osutils"
 	"github.com/docker/docker/pkg/term"
 )
 
+func writeMessage(f *os.File, level string, err error) {
+	fmt.Fprintf(f, `{"level": "%s","msg": "%s"}`, level, err)
+}
+
 // containerd-shim is a small shim that sits in front of a runtime implementation
 // that allows it to be repartented to init and handle reattach from the caller.
 //
@@ -28,9 +31,7 @@ func main() {
 	if err != nil {
 		panic(err)
 	}
-	logrus.SetOutput(f)
-	logrus.SetFormatter(&logrus.JSONFormatter{})
-	if err := start(); err != nil {
+	if err := start(f); err != nil {
 		// this means that the runtime failed starting the container and will have the
 		// proper error messages in the runtime log so we should to treat this as a
 		// shim failure because the sim executed properly
@@ -41,13 +42,13 @@ func main() {
 		// log the error instead of writing to stderr because the shim will have
 		// /dev/null as it's stdio because it is supposed to be reparented to system
 		// init and will not have anyone to read from it
-		logrus.Error(err)
+		writeMessage(f, "error", err)
 		f.Close()
 		os.Exit(1)
 	}
 }
 
-func start() error {
+func start(log *os.File) error {
 	// start handling signals as soon as possible so that things are properly reaped
 	// or if runtime exits before we hit the handler
 	signals := make(chan os.Signal, 2048)
@@ -73,7 +74,7 @@ func start() error {
 	}
 	defer func() {
 		if err := p.Close(); err != nil {
-			logrus.Warn(err)
+			writeMessage(log, "warn", err)
 		}
 	}()
 	if err := p.start(); err != nil {
@@ -84,7 +85,7 @@ func start() error {
 		for {
 			var msg, w, h int
 			if _, err := fmt.Fscanf(control, "%d %d %d\n", &msg, &w, &h); err != nil {
-				logrus.Warn(err)
+				continue
 			}
 			switch msg {
 			case 0:
@@ -108,21 +109,12 @@ func start() error {
 	for s := range signals {
 		switch s {
 		case syscall.SIGCHLD:
-			exits, err := osutils.Reap()
-			if err != nil {
-				logrus.Warn(err)
-			}
+			exits, _ := osutils.Reap()
 			for _, e := range exits {
 				// check to see if runtime is one of the processes that has exited
 				if e.Pid == p.pid() {
 					exitShim = true
-					logrus.WithFields(logrus.Fields{
-						"pid":    e.Pid,
-						"status": e.Status,
-					}).Info("shim: runtime exited")
-					if err := writeInt("exitStatus", e.Status); err != nil {
-						logrus.WithFields(logrus.Fields{"status": e.Status}).Warn(err)
-					}
+					writeInt("exitStatus", e.Status)
 				}
 			}
 		}

containerd-shim/process.go

@@ -12,13 +12,41 @@ import (
 	"strconv"
 	"sync"
 	"syscall"
+	"time"
 
-	"github.com/docker/containerd/runtime"
-	"github.com/opencontainers/runc/libcontainer"
+	"github.com/docker/containerd/specs"
 )
 
 var errRuntime = errors.New("shim: runtime execution error")
 
+type checkpoint struct {
+	// Timestamp is the time that checkpoint happened
+	Created time.Time `json:"created"`
+	// Name is the name of the checkpoint
+	Name string `json:"name"`
+	// Tcp checkpoints open tcp connections
+	Tcp bool `json:"tcp"`
+	// UnixSockets persists unix sockets in the checkpoint
+	UnixSockets bool `json:"unixSockets"`
+	// Shell persists tty sessions in the checkpoint
+	Shell bool `json:"shell"`
+	// Exit exits the container after the checkpoint is finished
+	Exit bool `json:"exit"`
+}
+
+type processState struct {
+	specs.ProcessSpec
+	Exec        bool     `json:"exec"`
+	Stdin       string   `json:"containerdStdin"`
+	Stdout      string   `json:"containerdStdout"`
+	Stderr      string   `json:"containerdStderr"`
+	RuntimeArgs []string `json:"runtimeArgs"`
+	NoPivotRoot bool     `json:"noPivotRoot"`
+	Checkpoint  string   `json:"checkpoint"`
+	RootUID     int      `json:"rootUID"`
+	RootGID     int      `json:"rootGID"`
+}
+
 type process struct {
 	sync.WaitGroup
 	id           string
@@ -26,12 +54,12 @@ type process struct {
 	stdio        *stdio
 	exec         bool
 	containerPid int
-	checkpoint   *runtime.Checkpoint
+	checkpoint   *checkpoint
 	shimIO       *IO
 	stdinCloser  io.Closer
-	console      libcontainer.Console
+	console      *os.File
 	consolePath  string
-	state        *runtime.ProcessState
+	state        *processState
 	runtime      string
 }
 
@@ -59,26 +87,26 @@ func newProcess(id, bundle, runtimeName string) (*process, error) {
 	return p, nil
 }
 
-func loadProcess() (*runtime.ProcessState, error) {
+func loadProcess() (*processState, error) {
 	f, err := os.Open("process.json")
 	if err != nil {
 		return nil, err
 	}
 	defer f.Close()
-	var s runtime.ProcessState
+	var s processState
 	if err := json.NewDecoder(f).Decode(&s); err != nil {
 		return nil, err
 	}
 	return &s, nil
 }
 
-func loadCheckpoint(bundle, name string) (*runtime.Checkpoint, error) {
+func loadCheckpoint(bundle, name string) (*checkpoint, error) {
 	f, err := os.Open(filepath.Join(bundle, "checkpoints", name, "config.json"))
 	if err != nil {
 		return nil, err
 	}
 	defer f.Close()
-	var cpt runtime.Checkpoint
+	var cpt checkpoint
 	if err := json.NewDecoder(f).Decode(&cpt); err != nil {
 		return nil, err
 	}
@@ -200,25 +228,25 @@ func (p *process) openIO() error {
 	}()
 
 	if p.state.Terminal {
-		console, err := libcontainer.NewConsole(uid, gid)
+		master, console, err := newConsole(uid, gid)
 		if err != nil {
 			return err
 		}
-		p.console = console
-		p.consolePath = console.Path()
+		p.console = master
+		p.consolePath = console
 		stdin, err := os.OpenFile(p.state.Stdin, syscall.O_RDONLY, 0)
 		if err != nil {
 			return err
 		}
-		go io.Copy(console, stdin)
+		go io.Copy(master, stdin)
 		stdout, err := os.OpenFile(p.state.Stdout, syscall.O_RDWR, 0)
 		if err != nil {
 			return err
 		}
 		p.Add(1)
 		go func() {
-			io.Copy(stdout, console)
-			console.Close()
+			io.Copy(stdout, master)
+			master.Close()
 			p.Done()
 		}()
 		return nil

osutils/reaper.go

@@ -2,11 +2,7 @@
 
 package osutils
 
-import (
-	"syscall"
-
-	"github.com/opencontainers/runc/libcontainer/utils"
-)
+import "syscall"
 
 // Exit is the wait4 information from an exited process
 type Exit struct {
@@ -34,7 +30,18 @@ func Reap() (exits []Exit, err error) {
 		}
 		exits = append(exits, Exit{
 			Pid:    pid,
-			Status: utils.ExitStatus(ws),
+			Status: exitStatus(ws),
 		})
 	}
 }
+
+const exitSignalOffset = 128
+
+// exitStatus returns the correct exit status for a process based on if it
+// was signaled or exited cleanly
+func exitStatus(status syscall.WaitStatus) int {
+	if status.Signaled() {
+		return exitSignalOffset + int(status.Signal())
+	}
+	return status.ExitStatus()
+}