package slack import ( "encoding/json" "fmt" "io" "net/http" "reflect" "time" "github.com/gorilla/websocket" ) // ManageConnection can be called on a Slack RTM instance returned by the // NewRTM method. It will connect to the slack RTM API and handle all incoming // and outgoing events. If a connection fails then it will attempt to reconnect // and will notify any listeners through an error event on the IncomingEvents // channel. // // If the connection ends and the disconnect was unintentional then this will // attempt to reconnect. // // This should only be called once per slack API! Otherwise expect undefined // behavior. // // The defined error events are located in websocket_internals.go. func (rtm *RTM) ManageConnection() { var ( err error info *Info conn *websocket.Conn ) for connectionCount := 0; ; connectionCount++ { // start trying to connect // the returned err is already passed onto the IncomingEvents channel if info, conn, err = rtm.connect(connectionCount, rtm.useRTMStart); err != nil { // when the connection is unsuccessful its fatal, and we need to bail out. rtm.Debugf("Failed to connect with RTM on try %d: %s", connectionCount, err) return } // lock to prevent data races with Disconnect particularly around isConnected // and conn. rtm.mu.Lock() rtm.conn = conn rtm.isConnected = true rtm.info = info rtm.mu.Unlock() rtm.IncomingEvents <- RTMEvent{"connected", &ConnectedEvent{ ConnectionCount: connectionCount, Info: info, }} rtm.Debugf("RTM connection succeeded on try %d", connectionCount) keepRunning := make(chan bool) // we're now connected (or have failed fatally) so we can set up // listeners go rtm.handleIncomingEvents(keepRunning) // this should be a blocking call until the connection has ended rtm.handleEvents(keepRunning) // after being disconnected we need to check if it was intentional // if not then we should try to reconnect if rtm.wasIntentional { return } // else continue and run the loop again to connect } } // connect attempts to connect to the slack websocket API. It handles any // errors that occur while connecting and will return once a connection // has been successfully opened. // If useRTMStart is false then it uses rtm.connect to create the connection, // otherwise it uses rtm.start. func (rtm *RTM) connect(connectionCount int, useRTMStart bool) (*Info, *websocket.Conn, error) { const ( errInvalidAuth = "invalid_auth" errInactiveAccount = "account_inactive" errMissingAuthToken = "not_authed" ) // used to provide exponential backoff wait time with jitter before trying // to connect to slack again boff := &backoff{ Min: 100 * time.Millisecond, Max: 5 * time.Minute, Factor: 2, Jitter: true, } for { // send connecting event rtm.IncomingEvents <- RTMEvent{"connecting", &ConnectingEvent{ Attempt: boff.attempts + 1, ConnectionCount: connectionCount, }} // attempt to start the connection info, conn, err := rtm.startRTMAndDial(useRTMStart) if err == nil { return info, conn, nil } // check for fatal errors switch err.Error() { case errInvalidAuth, errInactiveAccount, errMissingAuthToken: rtm.Debugf("Invalid auth when connecting with RTM: %s", err) rtm.IncomingEvents <- RTMEvent{"invalid_auth", &InvalidAuthEvent{}} return nil, nil, err default: } // any other errors are treated as recoverable and we try again after // sending the event along the IncomingEvents channel rtm.IncomingEvents <- RTMEvent{"connection_error", &ConnectionErrorEvent{ Attempt: boff.attempts, ErrorObj: err, }} // check if Disconnect() has been invoked. select { case <-rtm.disconnected: rtm.IncomingEvents <- RTMEvent{"disconnected", &DisconnectedEvent{Intentional: true}} return nil, nil, fmt.Errorf("disconnect received while trying to connect") default: } // get time we should wait before attempting to connect again dur := boff.Duration() rtm.Debugf("reconnection %d failed: %s", boff.attempts+1, err) rtm.Debugln(" -> reconnecting in", dur) time.Sleep(dur) } } // startRTMAndDial attempts to connect to the slack websocket. If useRTMStart is true, // then it returns the full information returned by the "rtm.start" method on the // slack API. Else it uses the "rtm.connect" method to connect func (rtm *RTM) startRTMAndDial(useRTMStart bool) (info *Info, _ *websocket.Conn, err error) { var ( url string ) if useRTMStart { rtm.Debugf("Starting RTM") info, url, err = rtm.StartRTM() } else { rtm.Debugf("Connecting to RTM") info, url, err = rtm.ConnectRTM() } if err != nil { rtm.Debugf("Failed to start or connect to RTM: %s", err) return nil, nil, err } rtm.Debugf("Dialing to websocket on url %s", url) // Only use HTTPS for connections to prevent MITM attacks on the connection. upgradeHeader := http.Header{} upgradeHeader.Add("Origin", "https://api.slack.com") dialer := websocket.DefaultDialer if rtm.dialer != nil { dialer = rtm.dialer } conn, _, err := dialer.Dial(url, upgradeHeader) if err != nil { rtm.Debugf("Failed to dial to the websocket: %s", err) return nil, nil, err } return info, conn, err } // killConnection stops the websocket connection and signals to all goroutines // that they should cease listening to the connection for events. // // This should not be called directly! Instead a boolean value (true for // intentional, false otherwise) should be sent to the killChannel on the RTM. func (rtm *RTM) killConnection(keepRunning chan bool, intentional bool) error { rtm.Debugln("killing connection") if rtm.isConnected { close(keepRunning) } rtm.isConnected = false rtm.wasIntentional = intentional err := rtm.conn.Close() rtm.IncomingEvents <- RTMEvent{"disconnected", &DisconnectedEvent{intentional}} return err } // handleEvents is a blocking function that handles all events. This sends // pings when asked to (on rtm.forcePing) and upon every given elapsed // interval. This also sends outgoing messages that are received from the RTM's // outgoingMessages channel. This also handles incoming raw events from the RTM // rawEvents channel. func (rtm *RTM) handleEvents(keepRunning chan bool) { ticker := time.NewTicker(rtm.pingInterval) defer ticker.Stop() for { select { // catch "stop" signal on channel close case intentional := <-rtm.killChannel: _ = rtm.killConnection(keepRunning, intentional) return // detect when the connection is dead. case <-rtm.pingDeadman.C: rtm.Debugln("deadman switch trigger disconnecting") _ = rtm.killConnection(keepRunning, false) // send pings on ticker interval case <-ticker.C: err := rtm.ping() if err != nil { _ = rtm.killConnection(keepRunning, false) return } case <-rtm.forcePing: err := rtm.ping() if err != nil { _ = rtm.killConnection(keepRunning, false) return } // listen for messages that need to be sent case msg := <-rtm.outgoingMessages: rtm.sendOutgoingMessage(msg) // listen for incoming messages that need to be parsed case rawEvent := <-rtm.rawEvents: switch rtm.handleRawEvent(rawEvent) { case rtmEventTypeGoodbye: _ = rtm.killConnection(keepRunning, false) default: } } } } // handleIncomingEvents monitors the RTM's opened websocket for any incoming // events. It pushes the raw events onto the RTM channel rawEvents. // // This will stop executing once the RTM's keepRunning channel has been closed // or has anything sent to it. func (rtm *RTM) handleIncomingEvents(keepRunning <-chan bool) { for { // non-blocking listen to see if channel is closed select { // catch "stop" signal on channel close case <-keepRunning: return default: if err := rtm.receiveIncomingEvent(); err != nil { return } } } } func (rtm *RTM) sendWithDeadline(msg interface{}) error { // set a write deadline on the connection if err := rtm.conn.SetWriteDeadline(time.Now().Add(10 * time.Second)); err != nil { return err } if err := rtm.conn.WriteJSON(msg); err != nil { return err } // remove write deadline return rtm.conn.SetWriteDeadline(time.Time{}) } // sendOutgoingMessage sends the given OutgoingMessage to the slack websocket. // // It does not currently detect if a outgoing message fails due to a disconnect // and instead lets a future failed 'PING' detect the failed connection. func (rtm *RTM) sendOutgoingMessage(msg OutgoingMessage) { rtm.Debugln("Sending message:", msg) if len(msg.Text) > MaxMessageTextLength { rtm.IncomingEvents <- RTMEvent{"outgoing_error", &MessageTooLongEvent{ Message: msg, MaxLength: MaxMessageTextLength, }} return } if err := rtm.sendWithDeadline(msg); err != nil { rtm.IncomingEvents <- RTMEvent{"outgoing_error", &OutgoingErrorEvent{ Message: msg, ErrorObj: err, }} // TODO force ping? } } // ping sends a 'PING' message to the RTM's websocket. If the 'PING' message // fails to send then this returns an error signifying that the connection // should be considered disconnected. // // This does not handle incoming 'PONG' responses but does store the time of // each successful 'PING' send so latency can be detected upon a 'PONG' // response. func (rtm *RTM) ping() error { id := rtm.idGen.Next() rtm.Debugln("Sending PING ", id) msg := &Ping{ID: id, Type: "ping", Timestamp: time.Now().Unix()} if err := rtm.sendWithDeadline(msg); err != nil { rtm.Debugf("RTM Error sending 'PING %d': %s", id, err.Error()) return err } return nil } // receiveIncomingEvent attempts to receive an event from the RTM's websocket. // This will block until a frame is available from the websocket. // If the read from the websocket results in a fatal error, this function will return non-nil. func (rtm *RTM) receiveIncomingEvent() error { event := json.RawMessage{} err := rtm.conn.ReadJSON(&event) switch { case err == io.ErrUnexpectedEOF: // EOF's don't seem to signify a failed connection so instead we ignore // them here and detect a failed connection upon attempting to send a // 'PING' message // trigger a 'PING' to detect potential websocket disconnect rtm.forcePing <- true case err != nil: // All other errors from ReadJSON come from NextReader, and should // kill the read loop and force a reconnect. rtm.IncomingEvents <- RTMEvent{"incoming_error", &IncomingEventError{ ErrorObj: err, }} rtm.killChannel <- false return err case len(event) == 0: rtm.Debugln("Received empty event") default: rtm.Debugln("Incoming Event:", string(event[:])) rtm.rawEvents <- event } return nil } // handleRawEvent takes a raw JSON message received from the slack websocket // and handles the encoded event. // returns the event type of the message. func (rtm *RTM) handleRawEvent(rawEvent json.RawMessage) string { event := &Event{} err := json.Unmarshal(rawEvent, event) if err != nil { rtm.IncomingEvents <- RTMEvent{"unmarshalling_error", &UnmarshallingErrorEvent{err}} return "" } switch event.Type { case rtmEventTypeAck: rtm.handleAck(rawEvent) case rtmEventTypeHello: rtm.IncomingEvents <- RTMEvent{"hello", &HelloEvent{}} case rtmEventTypePong: rtm.handlePong(rawEvent) case rtmEventTypeGoodbye: // just return the event type up for goodbye, will be handled by caller. case rtmEventTypeDesktopNotification: rtm.Debugln("Received desktop notification, ignoring") default: rtm.handleEvent(event.Type, rawEvent) } return event.Type } // handleAck handles an incoming 'ACK' message. func (rtm *RTM) handleAck(event json.RawMessage) { ack := &AckMessage{} if err := json.Unmarshal(event, ack); err != nil { rtm.Debugln("RTM Error unmarshalling 'ack' event:", err) rtm.Debugln(" -> Erroneous 'ack' event:", string(event)) return } if ack.Ok { rtm.IncomingEvents <- RTMEvent{"ack", ack} } else if ack.RTMResponse.Error != nil { // As there is no documentation for RTM error-codes, this // identification of a rate-limit warning is very brittle. if ack.RTMResponse.Error.Code == -1 && ack.RTMResponse.Error.Msg == "slow down, too many messages..." { rtm.IncomingEvents <- RTMEvent{"ack_error", &RateLimitEvent{}} } else { rtm.IncomingEvents <- RTMEvent{"ack_error", &AckErrorEvent{ack.Error}} } } else { rtm.IncomingEvents <- RTMEvent{"ack_error", &AckErrorEvent{fmt.Errorf("ack decode failure")}} } } // handlePong handles an incoming 'PONG' message which should be in response to // a previously sent 'PING' message. This is then used to compute the // connection's latency. func (rtm *RTM) handlePong(event json.RawMessage) { var ( p Pong ) rtm.resetDeadman() if err := json.Unmarshal(event, &p); err != nil { logger.Println("RTM Error unmarshalling 'pong' event:", err) rtm.Debugln(" -> Erroneous 'ping' event:", string(event)) return } latency := time.Since(time.Unix(p.Timestamp, 0)) rtm.IncomingEvents <- RTMEvent{"latency_report", &LatencyReport{Value: latency}} } // handleEvent is the "default" response to an event that does not have a // special case. It matches the command's name to a mapping of defined events // and then sends the corresponding event struct to the IncomingEvents channel. // If the event type is not found or the event cannot be unmarshalled into the // correct struct then this sends an UnmarshallingErrorEvent to the // IncomingEvents channel. func (rtm *RTM) handleEvent(typeStr string, event json.RawMessage) { v, exists := EventMapping[typeStr] if !exists { rtm.Debugf("RTM Error, received unmapped event %q: %s\n", typeStr, string(event)) err := fmt.Errorf("RTM Error: Received unmapped event %q: %s\n", typeStr, string(event)) rtm.IncomingEvents <- RTMEvent{"unmarshalling_error", &UnmarshallingErrorEvent{err}} return } t := reflect.TypeOf(v) recvEvent := reflect.New(t).Interface() err := json.Unmarshal(event, recvEvent) if err != nil { rtm.Debugf("RTM Error, could not unmarshall event %q: %s\n", typeStr, string(event)) err := fmt.Errorf("RTM Error: Could not unmarshall event %q: %s\n", typeStr, string(event)) rtm.IncomingEvents <- RTMEvent{"unmarshalling_error", &UnmarshallingErrorEvent{err}} return } rtm.IncomingEvents <- RTMEvent{typeStr, recvEvent} } // EventMapping holds a mapping of event names to their corresponding struct // implementations. The structs should be instances of the unmarshalling // target for the matching event type. var EventMapping = map[string]interface{}{ "message": MessageEvent{}, "presence_change": PresenceChangeEvent{}, "user_typing": UserTypingEvent{}, "channel_marked": ChannelMarkedEvent{}, "channel_created": ChannelCreatedEvent{}, "channel_joined": ChannelJoinedEvent{}, "channel_left": ChannelLeftEvent{}, "channel_deleted": ChannelDeletedEvent{}, "channel_rename": ChannelRenameEvent{}, "channel_archive": ChannelArchiveEvent{}, "channel_unarchive": ChannelUnarchiveEvent{}, "channel_history_changed": ChannelHistoryChangedEvent{}, "dnd_updated": DNDUpdatedEvent{}, "dnd_updated_user": DNDUpdatedEvent{}, "im_created": IMCreatedEvent{}, "im_open": IMOpenEvent{}, "im_close": IMCloseEvent{}, "im_marked": IMMarkedEvent{}, "im_history_changed": IMHistoryChangedEvent{}, "group_marked": GroupMarkedEvent{}, "group_open": GroupOpenEvent{}, "group_joined": GroupJoinedEvent{}, "group_left": GroupLeftEvent{}, "group_close": GroupCloseEvent{}, "group_rename": GroupRenameEvent{}, "group_archive": GroupArchiveEvent{}, "group_unarchive": GroupUnarchiveEvent{}, "group_history_changed": GroupHistoryChangedEvent{}, "file_created": FileCreatedEvent{}, "file_shared": FileSharedEvent{}, "file_unshared": FileUnsharedEvent{}, "file_public": FilePublicEvent{}, "file_private": FilePrivateEvent{}, "file_change": FileChangeEvent{}, "file_deleted": FileDeletedEvent{}, "file_comment_added": FileCommentAddedEvent{}, "file_comment_edited": FileCommentEditedEvent{}, "file_comment_deleted": FileCommentDeletedEvent{}, "pin_added": PinAddedEvent{}, "pin_removed": PinRemovedEvent{}, "star_added": StarAddedEvent{}, "star_removed": StarRemovedEvent{}, "reaction_added": ReactionAddedEvent{}, "reaction_removed": ReactionRemovedEvent{}, "pref_change": PrefChangeEvent{}, "team_join": TeamJoinEvent{}, "team_rename": TeamRenameEvent{}, "team_pref_change": TeamPrefChangeEvent{}, "team_domain_change": TeamDomainChangeEvent{}, "team_migration_started": TeamMigrationStartedEvent{}, "manual_presence_change": ManualPresenceChangeEvent{}, "user_change": UserChangeEvent{}, "emoji_changed": EmojiChangedEvent{}, "commands_changed": CommandsChangedEvent{}, "email_domain_changed": EmailDomainChangedEvent{}, "bot_added": BotAddedEvent{}, "bot_changed": BotChangedEvent{}, "accounts_changed": AccountsChangedEvent{}, "reconnect_url": ReconnectUrlEvent{}, "member_joined_channel": MemberJoinedChannelEvent{}, "member_left_channel": MemberLeftChannelEvent{}, }