[MM-35077] Add basic support for plugin intra-cluster communication (#17495)

* Add basic support for plugin intra-cluster communication

* Some renaming for added clarity

* Allow sending cluster event to specific nodes

* Improve naming and documentation

* Improve logging

app/busy_test.go

@@ -120,6 +120,10 @@ func (c *ClusterMock) SendClusterMessage(msg *model.ClusterMessage) {
 	c.Busy.ClusterEventChanged(sbs)
 }
 
+func (c *ClusterMock) SendClusterMessageToNode(nodeID string, msg *model.ClusterMessage) error {
+	return nil
+}
+
 func (c *ClusterMock) StartInterNodeCommunication() {}
 func (c *ClusterMock) StopInterNodeCommunication()  {}
 func (c *ClusterMock) RegisterClusterMessageHandler(event string, crm einterfaces.ClusterMessageHandler) {

app/cluster_handlers.go

@@ -20,6 +20,7 @@ func (a *App) registerAppClusterMessageHandlers() {
 	a.Cluster().RegisterClusterMessageHandler(model.CLUSTER_EVENT_CLEAR_SESSION_CACHE_FOR_ALL_USERS, a.clusterClearSessionCacheForAllUsersHandler)
 	a.Cluster().RegisterClusterMessageHandler(model.CLUSTER_EVENT_INSTALL_PLUGIN, a.clusterInstallPluginHandler)
 	a.Cluster().RegisterClusterMessageHandler(model.CLUSTER_EVENT_REMOVE_PLUGIN, a.clusterRemovePluginHandler)
+	a.Cluster().RegisterClusterMessageHandler(model.CLUSTER_EVENT_PLUGIN_EVENT, a.clusterPluginEventHandler)
 }
 
 func (a *App) clusterClearSessionCacheForUserHandler(msg *model.ClusterMessage) {
@@ -34,6 +35,35 @@ func (a *App) clusterInstallPluginHandler(msg *model.ClusterMessage) {
 	a.InstallPluginFromData(model.PluginEventDataFromJson(strings.NewReader(msg.Data)))
 }
 
+func (a *App) clusterPluginEventHandler(msg *model.ClusterMessage) {
+	env := a.GetPluginsEnvironment()
+	if env == nil {
+		return
+	}
+	if msg.Props == nil {
+		mlog.Warn("ClusterMessage.Props for plugin event should not be nil")
+		return
+	}
+	pluginID := msg.Props["PluginID"]
+	eventID := msg.Props["EventID"]
+	if pluginID == "" || eventID == "" {
+		mlog.Warn("Invalid ClusterMessage.Props values for plugin event",
+			mlog.String("plugin_id", pluginID), mlog.String("event_id", eventID))
+		return
+	}
+
+	hooks, err := env.HooksForPlugin(pluginID)
+	if err != nil {
+		mlog.Warn("Getting hooks for plugin failed", mlog.String("plugin_id", pluginID), mlog.Err(err))
+		return
+	}
+
+	hooks.OnPluginClusterEvent(a.PluginContext(), model.PluginClusterEvent{
+		Id:   eventID,
+		Data: []byte(msg.Data),
+	})
+}
+
 func (a *App) clusterRemovePluginHandler(msg *model.ClusterMessage) {
 	a.RemovePluginFromData(model.PluginEventDataFromJson(strings.NewReader(msg.Data)))
 }

app/plugin_api.go

@@ -1063,3 +1063,34 @@ func (api *PluginAPI) DeleteCommand(commandID string) error {
 
 	return nil
 }
+
+// PublishPluginClusterEvent broadcasts a plugin event to all other running instances of
+// the calling plugin.
+func (api *PluginAPI) PublishPluginClusterEvent(ev model.PluginClusterEvent,
+	opts model.PluginClusterEventSendOptions) error {
+	if api.app.Cluster() == nil {
+		return nil
+	}
+
+	msg := &model.ClusterMessage{
+		Event:            model.CLUSTER_EVENT_PLUGIN_EVENT,
+		SendType:         opts.SendType,
+		WaitForAllToSend: false,
+		Props: map[string]string{
+			"PluginID": api.id,
+			"EventID":  ev.Id,
+		},
+		Data: string(ev.Data),
+	}
+
+	// If TargetId is empty we broadcast to all other cluster nodes.
+	if opts.TargetId == "" {
+		api.app.Cluster().SendClusterMessage(msg)
+	} else {
+		if err := api.app.Cluster().SendClusterMessageToNode(opts.TargetId, msg); err != nil {
+			return fmt.Errorf("failed to send message to cluster node %q: %w", opts.TargetId, err)
+		}
+	}
+
+	return nil
+}