Serialize CommandHooks to state

This is needed to make 'runc delete' correctly run the post-stop hooks.

Signed-off-by: Julian Friedman <julz.friedman@uk.ibm.com>
Signed-off-by: Ed King <eking@pivotal.io>

libcontainer/configs/config.go

@@ -4,6 +4,8 @@ import (
 	"bytes"
 	"encoding/json"
 	"os/exec"
+
+	"github.com/Sirupsen/logrus"
 )
 
 type Rlimit struct {
@@ -175,8 +177,8 @@ type Config struct {
 	NoNewPrivileges bool `json:"no_new_privileges"`
 
 	// Hooks are a collection of actions to perform at various container lifecycle events.
-	// Hooks are not able to be marshaled to json but they are also not needed to.
-	Hooks *Hooks `json:"-"`
+	// CommandHooks are serialized to JSON, but other hooks are not.
+	Hooks *Hooks
 
 	// Version is the version of opencontainer specification that is supported.
 	Version string `json:"version"`
@@ -197,6 +199,52 @@ type Hooks struct {
 	Poststop []Hook
 }
 
+func (hooks *Hooks) UnmarshalJSON(b []byte) error {
+	var state struct {
+		Prestart  []CommandHook
+		Poststart []CommandHook
+		Poststop  []CommandHook
+	}
+
+	if err := json.Unmarshal(b, &state); err != nil {
+		return err
+	}
+
+	deserialize := func(shooks []CommandHook) (hooks []Hook) {
+		for _, shook := range shooks {
+			hooks = append(hooks, shook)
+		}
+
+		return hooks
+	}
+
+	hooks.Prestart = deserialize(state.Prestart)
+	hooks.Poststart = deserialize(state.Poststart)
+	hooks.Poststop = deserialize(state.Poststop)
+	return nil
+}
+
+func (hooks Hooks) MarshalJSON() ([]byte, error) {
+	serialize := func(hooks []Hook) (serializableHooks []CommandHook) {
+		for _, hook := range hooks {
+			switch chook := hook.(type) {
+			case CommandHook:
+				serializableHooks = append(serializableHooks, chook)
+			default:
+				logrus.Warnf("cannot serialize hook of type %T, skipping", hook)
+			}
+		}
+
+		return serializableHooks
+	}
+
+	return json.Marshal(map[string]interface{}{
+		"prestart":  serialize(hooks.Prestart),
+		"poststart": serialize(hooks.Poststart),
+		"poststop":  serialize(hooks.Poststop),
+	})
+}
+
 // HookState is the payload provided to a hook on execution.
 type HookState struct {
 	Version string `json:"version"`

libcontainer/factory_linux_test.go

@@ -6,6 +6,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"reflect"
 	"syscall"
 	"testing"
 
@@ -132,9 +133,22 @@ func TestFactoryLoadContainer(t *testing.T) {
 	defer os.RemoveAll(root)
 	// setup default container config and state for mocking
 	var (
-		id             = "1"
+		id            = "1"
+		expectedHooks = &configs.Hooks{
+			Prestart: []configs.Hook{
+				configs.CommandHook{Command: configs.Command{Path: "prestart-hook"}},
+			},
+			Poststart: []configs.Hook{
+				configs.CommandHook{Command: configs.Command{Path: "poststart-hook"}},
+			},
+			Poststop: []configs.Hook{
+				unserializableHook{},
+				configs.CommandHook{Command: configs.Command{Path: "poststop-hook"}},
+			},
+		}
 		expectedConfig = &configs.Config{
 			Rootfs: "/mycontainer/root",
+			Hooks:  expectedHooks,
 		}
 		expectedState = &State{
 			BaseState: BaseState{
@@ -164,6 +178,10 @@ func TestFactoryLoadContainer(t *testing.T) {
 	if config.Rootfs != expectedConfig.Rootfs {
 		t.Fatalf("expected rootfs %q but received %q", expectedConfig.Rootfs, config.Rootfs)
 	}
+	expectedHooks.Poststop = expectedHooks.Poststop[1:] // expect unserializable hook to be skipped
+	if !reflect.DeepEqual(config.Hooks, expectedHooks) {
+		t.Fatalf("expects hooks %q but received %q", expectedHooks, config.Hooks)
+	}
 	lcontainer, ok := container.(*linuxContainer)
 	if !ok {
 		t.Fatal("expected linux container on linux based systems")
@@ -181,3 +199,9 @@ func marshal(path string, v interface{}) error {
 	defer f.Close()
 	return utils.WriteJSON(f, v)
 }
+
+type unserializableHook struct{}
+
+func (unserializableHook) Run(configs.HookState) error {
+	return nil
+}