MM-10702 Moving plugins to use hashicorp go-plugin. (#8978)

* Moving plugins to use hashicorp go-plugin.

* Tweaks from feedback.

plugin/supervisor.go

@@ -1,13 +1,99 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
-// See License.txt for license information.
+// See LICENSE.txt for license information.
 
 package plugin
 
-// Supervisor provides the interface for an object that controls the execution of a plugin. This
-// type is only relevant to the server, and isn't used by the plugins themselves.
-type Supervisor interface {
-	Start(API) error
-	Wait() error
-	Stop() error
-	Hooks() Hooks
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"github.com/hashicorp/go-plugin"
+	"github.com/mattermost/mattermost-server/mlog"
+	"github.com/mattermost/mattermost-server/model"
+)
+
+type Supervisor struct {
+	pluginId    string
+	client      *plugin.Client
+	hooks       Hooks
+	implemented [TotalHooksId]bool
+}
+
+func NewSupervisor(pluginInfo *model.BundleInfo, parentLogger *mlog.Logger, apiImpl API) (*Supervisor, error) {
+	supervisor := Supervisor{}
+
+	wrappedLogger := pluginInfo.WrapLogger(parentLogger)
+
+	hclogAdaptedLogger := &HclogAdapter{
+		wrappedLogger: wrappedLogger,
+		extrasKey:     "wrapped_extras",
+	}
+
+	pluginMap := map[string]plugin.Plugin{
+		"hooks": &HooksPlugin{
+			log:     wrappedLogger,
+			apiImpl: apiImpl,
+		},
+	}
+
+	executable := filepath.Clean(filepath.Join(".", pluginInfo.Manifest.Backend.Executable))
+	if strings.HasPrefix(executable, "..") {
+		return nil, fmt.Errorf("invalid backend executable")
+	}
+	executable = filepath.Join(pluginInfo.Path, executable)
+
+	supervisor.client = plugin.NewClient(&plugin.ClientConfig{
+		HandshakeConfig: Handshake,
+		Plugins:         pluginMap,
+		Cmd:             exec.Command(executable),
+		SyncStdout:      os.Stdout,
+		SyncStderr:      os.Stdout,
+		Logger:          hclogAdaptedLogger,
+		StartTimeout:    time.Second * 3,
+	})
+
+	rpcClient, err := supervisor.client.Client()
+	if err != nil {
+		return nil, err
+	}
+
+	raw, err := rpcClient.Dispense("hooks")
+	if err != nil {
+		return nil, err
+	}
+
+	supervisor.hooks = raw.(Hooks)
+
+	if impl, err := supervisor.hooks.Implemented(); err != nil {
+		return nil, err
+	} else {
+		for _, hookName := range impl {
+			if hookId, ok := HookNameToId[hookName]; ok {
+				supervisor.implemented[hookId] = true
+			}
+		}
+	}
+
+	err = supervisor.Hooks().OnActivate()
+	if err != nil {
+		return nil, err
+	}
+
+	return &supervisor, nil
+}
+
+func (sup *Supervisor) Shutdown() {
+	sup.client.Kill()
+}
+
+func (sup *Supervisor) Hooks() Hooks {
+	return sup.hooks
+}
+
+func (sup *Supervisor) Implements(hookId int) bool {
+	return sup.implemented[hookId]
 }