MM-57018: support reattaching plugins (#26421)

* ProfileImageBytes for EnsureBotOptions

* leverage plugintest.NewAPI

* fix linting

* add UpdateUserRoles to plugin api

* MM-57018: support reattaching plugins

Expose a local-only API for reattaching plugins: instead of the server starting and managing the process itself, allow the plugin to be launched externally (eg within a unit test) and reattach to an existing server instance to provide the unit test with a fully functional RPC API, sidestepping the need for mocking the plugin API in most cases.

In the future, this may become the basis for running plugins in a sidecar container.

Fixes: https://mattermost.atlassian.net/browse/MM-57018

* drop unused supervisor.pid

* factor out checkMinServerVersion

* factor out startPluginServer

* restore missing setPluginState on successful reattach

* avoid passing around a stale registeredPlugin

* inline initializePluginImplementation

* have IsValid return an error

* explicitly close rpcClient

In the case of reattached plugins, the Unix socket won't necessarily disappear leaving the muxBrokers blocked indefinitely. And `Kill()` doesn't do anything if there's no process being managed.

* explicitly detachPlugin

* emphasize gRPC not being supported

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

server/channels/api4/plugin_local.go

@@ -3,6 +3,13 @@
 
 package api4
 
+import (
+	"encoding/json"
+	"net/http"
+
+	"github.com/mattermost/mattermost/server/public/model"
+)
+
 func (api *API) InitPluginLocal() {
 	api.BaseRoutes.Plugins.Handle("", api.APILocal(uploadPlugin, handlerParamFileAPI)).Methods("POST")
 	api.BaseRoutes.Plugins.Handle("", api.APILocal(getPlugins)).Methods("GET")
@@ -12,4 +19,44 @@ func (api *API) InitPluginLocal() {
 	api.BaseRoutes.Plugin.Handle("/disable", api.APILocal(disablePlugin)).Methods("POST")
 	api.BaseRoutes.Plugins.Handle("/marketplace", api.APILocal(installMarketplacePlugin)).Methods("POST")
 	api.BaseRoutes.Plugins.Handle("/marketplace", api.APILocal(getMarketplacePlugins)).Methods("GET")
+	api.BaseRoutes.Plugins.Handle("/reattach", api.APILocal(reattachPlugin)).Methods("POST")
+	api.BaseRoutes.Plugin.Handle("/detach", api.APILocal(detachPlugin)).Methods("POST")
+}
+
+// reattachPlugin allows the server to bind to an existing plugin instance launched elsewhere.
+//
+// This API is only exposed over a local socket.
+func reattachPlugin(c *Context, w http.ResponseWriter, r *http.Request) {
+	var pluginReattachRequest model.PluginReattachRequest
+	if err := json.NewDecoder(r.Body).Decode(&pluginReattachRequest); err != nil {
+		c.Err = model.NewAppError("reattachPlugin", "api4.plugin.reattachPlugin.invalid_request", nil, err.Error(), http.StatusBadRequest)
+		return
+	}
+
+	if err := pluginReattachRequest.IsValid(); err != nil {
+		c.Err = err
+		return
+	}
+
+	err := c.App.ReattachPlugin(pluginReattachRequest.Manifest, pluginReattachRequest.PluginReattachConfig)
+	if err != nil {
+		c.Err = err
+		return
+	}
+}
+
+// detachPlugin detaches a previously reattached plugin.
+//
+// This API is only exposed over a local socket.
+func detachPlugin(c *Context, w http.ResponseWriter, r *http.Request) {
+	c.RequirePluginId()
+	if c.Err != nil {
+		return
+	}
+
+	err := c.App.DetachPlugin(c.Params.PluginId)
+	if err != nil {
+		c.Err = err
+		return
+	}
 }

server/channels/app/app_iface.go

@@ -129,6 +129,8 @@ type AppIface interface {
 	// DemoteUserToGuest Convert user's roles and all his membership's roles from
 	// regular user roles to guest roles.
 	DemoteUserToGuest(c request.CTX, user *model.User) *model.AppError
+	// DetachPlugin allows the server to bind to an existing plugin instance launched elsewhere.
+	DetachPlugin(pluginId string) *model.AppError
 	// DisablePlugin will set the config for an installed plugin to disabled, triggering deactivation if active.
 	// Notifies cluster peers through config change.
 	DisablePlugin(id string) *model.AppError
@@ -303,6 +305,8 @@ type AppIface interface {
 	// PromoteGuestToUser Convert user's roles and all his membership's roles from
 	// guest roles to regular user roles.
 	PromoteGuestToUser(c request.CTX, user *model.User, requestorId string) *model.AppError
+	// ReattachPlugin allows the server to bind to an existing plugin instance launched elsewhere.
+	ReattachPlugin(manifest *model.Manifest, pluginReattachConfig *model.PluginReattachConfig) *model.AppError
 	// Removes a listener function by the unique ID returned when AddConfigListener was called
 	RemoveConfigListener(id string)
 	// RenameChannel is used to rename the channel Name and the DisplayName fields

server/channels/app/opentracing/opentracing_layer.go

@@ -3741,6 +3741,28 @@ func (a *OpenTracingAppLayer) DemoteUserToGuest(c request.CTX, user *model.User)
 	return resultVar0
 }
 
+func (a *OpenTracingAppLayer) DetachPlugin(pluginId string) *model.AppError {
+	origCtx := a.ctx
+	span, newCtx := tracing.StartSpanWithParentByContext(a.ctx, "app.DetachPlugin")
+
+	a.ctx = newCtx
+	a.app.Srv().Store().SetContext(newCtx)
+	defer func() {
+		a.app.Srv().Store().SetContext(origCtx)
+		a.ctx = origCtx
+	}()
+
+	defer span.Finish()
+	resultVar0 := a.app.DetachPlugin(pluginId)
+
+	if resultVar0 != nil {
+		span.LogFields(spanlog.Error(resultVar0))
+		ext.Error.Set(span, true)
+	}
+
+	return resultVar0
+}
+
 func (a *OpenTracingAppLayer) DisableAutoResponder(rctx request.CTX, userID string, asAdmin bool) *model.AppError {
 	origCtx := a.ctx
 	span, newCtx := tracing.StartSpanWithParentByContext(a.ctx, "app.DisableAutoResponder")
@@ -13945,6 +13967,28 @@ func (a *OpenTracingAppLayer) ReadFile(path string) ([]byte, *model.AppError) {
 	return resultVar0, resultVar1
 }
 
+func (a *OpenTracingAppLayer) ReattachPlugin(manifest *model.Manifest, pluginReattachConfig *model.PluginReattachConfig) *model.AppError {
+	origCtx := a.ctx
+	span, newCtx := tracing.StartSpanWithParentByContext(a.ctx, "app.ReattachPlugin")
+
+	a.ctx = newCtx
+	a.app.Srv().Store().SetContext(newCtx)
+	defer func() {
+		a.app.Srv().Store().SetContext(origCtx)
+		a.ctx = origCtx
+	}()
+
+	defer span.Finish()
+	resultVar0 := a.app.ReattachPlugin(manifest, pluginReattachConfig)
+
+	if resultVar0 != nil {
+		span.LogFields(spanlog.Error(resultVar0))
+		ext.Error.Set(span, true)
+	}
+
+	return resultVar0
+}
+
 func (a *OpenTracingAppLayer) RecycleDatabaseConnection(rctx request.CTX) {
 	origCtx := a.ctx
 	span, newCtx := tracing.StartSpanWithParentByContext(a.ctx, "app.RecycleDatabaseConnection")

server/channels/app/plugin_reattach.go

@@ -0,0 +1,50 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+package app
+
+import (
+	"net/http"
+
+	"github.com/mattermost/mattermost/server/public/model"
+)
+
+// ReattachPlugin allows the server to bind to an existing plugin instance launched elsewhere.
+func (a *App) ReattachPlugin(manifest *model.Manifest, pluginReattachConfig *model.PluginReattachConfig) *model.AppError {
+	return a.ch.ReattachPlugin(manifest, pluginReattachConfig)
+}
+
+// ReattachPlugin allows the server to bind to an existing plugin instance launched elsewhere.
+func (ch *Channels) ReattachPlugin(manifest *model.Manifest, pluginReattachConfig *model.PluginReattachConfig) *model.AppError {
+	pluginsEnvironment := ch.GetPluginsEnvironment()
+	if pluginsEnvironment == nil {
+		return model.NewAppError("ReattachPlugin", "app.plugin.disabled.app_error", nil, "", http.StatusNotImplemented)
+	}
+
+	ch.DetachPlugin(manifest.Id)
+
+	// Reattach to the plugin
+	if err := pluginsEnvironment.Reattach(manifest, pluginReattachConfig); err != nil {
+		return model.NewAppError("ReattachPlugin", "app.plugin.reattach.app_error", nil, "", http.StatusInternalServerError).Wrap(err)
+	}
+
+	return nil
+}
+
+// DetachPlugin allows the server to bind to an existing plugin instance launched elsewhere.
+func (a *App) DetachPlugin(pluginId string) *model.AppError {
+	return a.ch.DetachPlugin(pluginId)
+}
+
+// DetachPlugin allows the server to bind to an existing plugin instance launched elsewhere.
+func (ch *Channels) DetachPlugin(pluginID string) *model.AppError {
+	pluginsEnvironment := ch.GetPluginsEnvironment()
+	if pluginsEnvironment == nil {
+		return model.NewAppError("DetachPlugin", "app.plugin.disabled.app_error", nil, "", http.StatusNotImplemented)
+	}
+
+	// Deactivate and remove any existing plugin, if present.
+	pluginsEnvironment.Deactivate(pluginID)
+	pluginsEnvironment.RemovePlugin(pluginID)
+
+	return nil
+}