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SocketModeClient.ts
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SocketModeClient.ts
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import { EventEmitter } from 'eventemitter3';
import WebSocket from 'ws'; // tslint:disable-line:import-name
import Finity, { StateMachine } from 'finity'; // tslint:disable-line:import-name
import {
WebClient,
AppsConnectionsOpenResponse,
WebAPICallError,
ErrorCode as APICallErrorCode,
addAppMetadata,
WebClientOptions,
} from '@slack/web-api';
import { LogLevel, Logger, getLogger } from './logger';
import {
websocketErrorWithOriginal,
sendWhileDisconnectedError,
sendWhileNotReadyError,
} from './errors';
const packageJson = require('../package.json'); // tslint:disable-line:no-require-imports no-var-requires
/**
* An Socket Mode Client allows programs to communicate with the
* [Slack Platform's Events API](https://api.slack.com/events-api) over a websocket.
* This object uses the EventEmitter pattern to dispatch incoming events and has a built in send method to
* acknowledge incoming events over the websocket.
*/
export class SocketModeClient extends EventEmitter {
/**
* Whether or not the client is currently connected to the web socket
*/
public connected: boolean = false;
/**
* Whether or not the client has authenticated to the Socket Mode API. This occurs when the connect method
* completes, and a WebSocket URL is available for the client's connection.
*/
public authenticated: boolean = false;
// public listenerIterator: AsyncGenerator | undefined;
/**
* Whether this client will automatically reconnect when (not manually) disconnected
*/
private autoReconnectEnabled: boolean;
/**
* The number of milliseconds to wait upon connection for reply messages from the previous connection. The default
* value is 2 seconds.
*/
// private replyAckOnReconnectTimeout: number;
/**
* State machine that backs the transition and action behavior
*/
private stateMachine: StateMachine<string, string>;
/**
* Configuration for the state machine
*/
private stateMachineConfig = Finity
.configure()
.initialState('disconnected')
.on('start').transitionTo('connecting')
// .onEnter(() => {})
.state('connecting')
.submachine(Finity.configure()
.initialState('authenticating')
.do(() => {
return this.webClient.apps.connections.open().then((result: AppsConnectionsOpenResponse) => {
return result;
}).catch((error) => {
this.logger.error(error);
// throw error;
return Promise.reject(error);
});
})
.onSuccess().transitionTo('authenticated')
.onFailure()
.transitionTo('reconnecting').withCondition((context) => {
const error = context.error as WebAPICallError;
this.logger.info(`unable to Socket Mode start: ${error.message}`);
// Observe this event when the error which causes reconnecting or disconnecting is meaningful
this.emit('unable_to_socket_mode_start', error);
let isRecoverable = true;
if (error.code === APICallErrorCode.PlatformError &&
(Object.values(UnrecoverableSocketModeStartError) as string[]).includes(error.data.error)) {
isRecoverable = false;
} else if (error.code === APICallErrorCode.RequestError) {
isRecoverable = false;
} else if (error.code === APICallErrorCode.HTTPError) {
isRecoverable = false;
}
return this.autoReconnectEnabled && isRecoverable;
})
.transitionTo('failed')
.state('authenticated')
.onEnter((_state, context) => {
this.authenticated = true;
this.setupWebSocket(context.result.url);
setImmediate(() => {
this.emit('authenticated', context.result);
});
})
.on('websocket open').transitionTo('handshaking')
.state('handshaking') // a state in which to wait until the 'server hello' event
.state('failed')
.onEnter((_state, context) => {
// dispatch 'failure' on parent machine to transition out of this submachine's states
this.stateMachine.handle('failure', context.error);
})
.global()
.onStateEnter((state) => {
this.logger.debug(`transitioning to state: connecting:${state}`);
})
.getConfig())
.on('server hello').transitionTo('connected')
.on('websocket close')
.transitionTo('reconnecting').withCondition(() => this.autoReconnectEnabled)
.transitionTo('disconnected').withAction(() => {
// this transition circumvents the 'disconnecting' state (since the websocket is already closed), so we need
// to execute its onExit behavior here.
this.teardownWebsocket();
})
.on('failure').transitionTo('disconnected')
.on('explicit disconnect').transitionTo('disconnecting')
.state('connected')
.onEnter(() => {
this.connected = true;
})
.submachine(Finity.configure()
.initialState('ready')
.onEnter(() => {
if (this.badConnection) {
// arrived here because `server ping timeout` occurred and a new connection was created
// tear down old connection
this.teardownWebsocket();
this.badConnection = false;
}
// start heartbeat to keep track of the websocket connection continuing to be alive
this.heartbeat();
// the transition isn't done yet, so we delay the following statement until after the event loop returns
setImmediate(() => {
this.emit('ready');
});
})
// tslint:disable-next-line: max-line-length
.on('server disconnect warning').transitionTo('refreshing-connection').withCondition(() => this.autoReconnectEnabled)
// tslint:disable-next-line: max-line-length
.on('server pings not received').transitionTo('refreshing-connection').withCondition(() => this.autoReconnectEnabled)
.on('server disconnect old socket').transitionTo('closing-socket')
.state('refreshing-connection')
.submachine(Finity.configure()
.initialState('authenticating')
.do(() => {
return this.webClient.apps.connections.open().then((result: AppsConnectionsOpenResponse) => {
return result;
}).catch((error) => {
this.logger.error(error);
// throw error;
return Promise.reject(error);
});
})
.onSuccess().transitionTo('authenticated')
.onFailure()
.transitionTo('authenticating').withCondition((context) => {
const error = context.error as WebAPICallError;
this.logger.info(`unable to Socket Mode start: ${error.message}`);
// Observe this event when the error which causes reconnecting or disconnecting is meaningful
this.emit('unable_to_socket_mode_start', error);
let isRecoverable = true;
if (error.code === APICallErrorCode.PlatformError &&
(Object.values(UnrecoverableSocketModeStartError) as string[]).includes(error.data.error)) {
isRecoverable = false;
} else if (error.code === APICallErrorCode.RequestError) {
isRecoverable = false;
} else if (error.code === APICallErrorCode.HTTPError) {
isRecoverable = false;
}
return this.autoReconnectEnabled && isRecoverable;
})
.transitionTo('failed')
.state('authenticated')
.onEnter((_state, context) => {
this.authenticated = true;
this.setupWebSocket(context.result.url);
setImmediate(() => {
this.emit('authenticated', context.result);
});
})
.on('websocket open').transitionTo('handshaking')
.state('handshaking') // a state in which to wait until the 'server hello' event
.state('failed')
.onEnter((_state, context) => {
// dispatch 'failure' on parent machine to transition out of this submachine's states
this.stateMachine.handle('failure', context.error);
})
.global()
.onStateEnter((state) => {
this.logger.debug(`transitioning to state: refreshing-connection:${state}`);
})
.getConfig())
.on('server hello').transitionTo('ready')
.on('websocket close')
.transitionTo('authenticating').withCondition(() => this.autoReconnectEnabled)
.transitionTo('disconnected').withAction(() => {
// this transition circumvents the 'disconnecting' state (since the websocket is already closed),
// so we need to execute its onExit behavior here.
this.teardownWebsocket();
})
.on('failure').transitionTo('disconnected')
.on('explicit disconnect').transitionTo('disconnecting')
.state('closing-socket')
.do(() => {
// stop heartbeat
if (this.pingTimeout !== undefined) {
clearTimeout(this.pingTimeout);
}
return Promise.resolve(true);
})
.onSuccess().transitionTo('ready')
.onExit(() => this.teardownWebsocket())
.global()
.onStateEnter((state) => {
this.logger.debug(`transitioning to state: connected:${state}`);
})
.getConfig())
.on('server disconnect warning')
.transitionTo('refreshing-connection').withCondition(() => this.autoReconnectEnabled)
.on('websocket close')
.transitionTo('reconnecting').withCondition(() => this.autoReconnectEnabled)
.transitionTo('disconnected').withAction(() => {
// this transition circumvents the 'disconnecting' state (since the websocket is already closed), so we need
// to execute its onExit behavior here.
this.teardownWebsocket();
})
.on('explicit disconnect').transitionTo('disconnecting')
.onExit(() => {
this.connected = false;
this.authenticated = false;
if (this.pingTimeout !== undefined) {
clearTimeout(this.pingTimeout);
}
})
.state('disconnecting')
.onEnter(() => {
// Most of the time, a websocket will exist. The only time it does not is when transitioning from connecting,
// before the client.start() has finished and the websocket hasn't been set up.
if (this.websocket !== undefined) {
this.websocket.close();
}
})
.on('websocket close').transitionTo('disconnected')
.onExit(() => this.teardownWebsocket())
// reconnecting is just like disconnecting, except that the websocket should already be closed before we enter
// this state, and that the next state should be connecting.
.state('reconnecting')
.do(() => {
if (this.pingTimeout !== undefined) {
clearTimeout(this.pingTimeout);
}
return Promise.resolve(true);
})
.onSuccess().transitionTo('connecting')
.onExit(() => this.teardownWebsocket())
.global()
.onStateEnter((state, context) => {
this.logger.debug(`transitioning to state: ${state}`);
if (state === 'disconnected') {
// Emits a `disconnected` event with a possible error object (might be undefined)
this.emit(state, context.eventPayload);
} else {
// Emits events: `connecting`, `connected`, `disconnecting`, `reconnecting`
this.emit(state);
}
})
.getConfig();
/**
* The client's websockets
*/
public websocket?: WebSocket;
private secondaryWebsocket?: WebSocket;
private webClient: WebClient;
/**
* The name used to prefix all logging generated from this object
*/
private static loggerName = 'SocketModeClient';
/**
* This object's logger instance
*/
private logger: Logger;
/**
* How long to wait for pings from server before timing out
*/
private clientPingTimeout: number;
/**
* reference to the timeout timer we use to listen to pings from the server
*/
private pingTimeout: NodeJS.Timeout | undefined;
/**
* Used to see if a websocket stops sending heartbeats and is deemed bad
*/
private badConnection: boolean = false;
/**
* WebClient options we pass to our WebClient instance
* We also reuse agent and tls for our websocket connection
*/
private clientOptions: WebClientOptions;
constructor({
logger = undefined,
logLevel = undefined,
autoReconnectEnabled = true,
clientPingTimeout = 30000,
appToken = undefined,
clientOptions = {},
}: SocketModeOptions = {}) {
super();
if (appToken === undefined) {
throw new Error('Must provide an App Level Token when initializing a Socket Mode Client');
}
this.clientPingTimeout = clientPingTimeout;
// Setup the logger
if (typeof logger !== 'undefined') {
this.logger = logger;
if (typeof logLevel !== 'undefined') {
this.logger.debug('The logLevel given to Socket Mode was ignored as you also gave logger');
}
} else {
this.logger = getLogger(SocketModeClient.loggerName, logLevel ?? LogLevel.INFO, logger);
}
this.clientOptions = clientOptions;
this.webClient = new WebClient('', {
logger,
logLevel: this.logger.getLevel(),
headers: { Authorization: `Bearer ${appToken}` },
...clientOptions,
});
this.autoReconnectEnabled = autoReconnectEnabled;
this.stateMachine = Finity.start(this.stateMachineConfig);
this.logger.debug('initialized');
}
/**
* Begin an Socket Mode session. This method must be called before any messages can
* be sent or received.
*/
public start(): Promise<AppsConnectionsOpenResponse> {
this.logger.debug('start()');
// delegate behavior to state machine
this.stateMachine.handle('start');
// return a promise that resolves with the connection information
return new Promise((resolve, reject) => {
this.once('authenticated', (result) => {
this.removeListener('disconnected', reject);
resolve(result);
});
this.once('disconnected', (err) => {
this.removeListener('authenticated', resolve);
reject(err);
});
});
}
/**
* End a Socket Mode session. After this method is called no messages will be sent or received unless you call
* start() again later.
*/
public disconnect(): Promise<void> {
return new Promise((resolve, reject) => {
this.logger.debug('manual disconnect');
// resolve (or reject) on disconnect
this.once('disconnected', (err) => {
if (err instanceof Error) {
reject(err);
} else {
resolve();
}
});
// delegate behavior to state machine
this.stateMachine.handle('explicit disconnect');
});
}
/**
* Method for sending an outgoing message of an arbitrary type over the websocket connection.
* Primarily used to send acknowledgements back to slack for incoming events
* @param id the envelope id
* @param body the message body
*/
private send(id: string, body = {}): Promise<void> {
const message = { envelope_id: id, payload: { ...body } };
return new Promise((resolve, reject) => {
this.logger.debug(`send() in state: ${this.stateMachine.getStateHierarchy()}`);
if (this.websocket === undefined) {
this.logger.error('cannot send message when client is not connected');
reject(sendWhileDisconnectedError());
} else if (!(this.stateMachine.getCurrentState() === 'connected' &&
this.stateMachine.getStateHierarchy()[1] === 'ready')) {
this.logger.error('cannot send message when client is not ready');
reject(sendWhileNotReadyError());
} else {
this.emit('outgoing_message', message);
const flatMessage = JSON.stringify(message);
this.logger.debug(`sending message on websocket: ${flatMessage}`);
this.websocket.send(flatMessage, (error) => {
if (error !== undefined) {
this.logger.error(`failed to send message on websocket: ${error.message}`);
return reject(websocketErrorWithOriginal(error));
}
resolve();
});
}
});
}
/**
* Set up method for the client's websocket instance. This method will attach event listeners.
*/
private setupWebSocket(url: string): void {
// initialize the websocket
const options: WebSocket.ClientOptions = {
perMessageDeflate: false,
agent: this.clientOptions.agent,
};
let websocket: WebSocket;
if (this.websocket === undefined) {
this.websocket = new WebSocket(url, options);
websocket = this.websocket;
} else {
// setup secondary websocket
// this is used when creating a new connection because the first is about to disconnect
this.secondaryWebsocket = new WebSocket(url, options);
websocket = this.secondaryWebsocket;
}
// attach event listeners
websocket.addEventListener('open', event => this.stateMachine.handle('websocket open', event));
websocket.addEventListener('close', event => this.stateMachine.handle('websocket close', event));
websocket.addEventListener('error', (event) => {
this.logger.error(`A websocket error occurred: ${event.message}`);
this.emit('error', websocketErrorWithOriginal(event.error));
});
websocket.addEventListener('message', this.onWebsocketMessage.bind(this));
// Confirm websocket connection is still active
websocket.addEventListener('ping', this.heartbeat.bind(this));
}
/**
* Tear down method for the client's websocket instance. This method undoes the work in setupWebSocket(url).
*/
private teardownWebsocket(): void {
if (this.secondaryWebsocket !== undefined && this.websocket !== undefined) {
this.logger.debug('secondary websocket exists, tear down first and assign second');
// currently have two websockets, so tear down the older one
this.websocket.removeAllListeners('open');
this.websocket.removeAllListeners('close');
this.websocket.removeAllListeners('error');
this.websocket.removeAllListeners('message');
this.websocket = this.secondaryWebsocket;
this.secondaryWebsocket = undefined;
} else if (this.secondaryWebsocket === undefined && this.websocket !== undefined) {
this.logger.debug('only primary websocket exists, tear it down');
// only one websocket to tear down
this.websocket.removeAllListeners('open');
this.websocket.removeAllListeners('close');
this.websocket.removeAllListeners('error');
this.websocket.removeAllListeners('message');
this.websocket = undefined;
}
}
/**
* confirms websocket connection is still active
* fires whenever a ping event is received
*/
private heartbeat(): void {
if (this.pingTimeout !== undefined) {
clearTimeout(this.pingTimeout);
}
// Don't start heartbeat if connection is already deemed bad
if (!this.badConnection) {
this.pingTimeout = setTimeout(() => {
this.logger.info(`A ping wasn't received from the server before the timeout of ${this.clientPingTimeout}ms!`);
if (this.stateMachine.getCurrentState() === 'connected'
&& this.stateMachine.getStateHierarchy()[1] === 'ready') {
this.badConnection = true;
// opens secondary websocket and teardown original once that is ready
this.stateMachine.handle('server pings not received');
}
// tslint:disable-next-line: align
}, this.clientPingTimeout);
}
}
/**
* `onmessage` handler for the client's websocket. This will parse the payload and dispatch the relevant events for
* each incoming message.
*/
private async onWebsocketMessage({ data }: { data: string }): Promise<void> {
this.logger.debug(`received a message on the WebSocket: ${data}`);
// parse message into slack event
let event: {
type: string;
reason: string;
payload: {[key: string]: any};
envelope_id: string;
};
try {
event = JSON.parse(data);
} catch (parseError) {
// prevent application from crashing on a bad message, but log an error to bring attention
this.logger.error(
`unable to parse incoming websocket message: ${parseError.message}`,
);
return;
}
// internal event handlers
if (event.type === 'hello') {
this.stateMachine.handle('server hello');
return;
}
// open second websocket connection in preparation for the existing websocket disconnecting
if (event.type === 'disconnect' && event.reason === 'warning') {
this.logger.debug('disconnect warning, creating second connection');
this.stateMachine.handle('server disconnect warning');
return;
}
// close primary websocket in favor of secondary websocket, assign secondary to primary
if (event.type === 'disconnect' && event.reason === 'refresh_requested') {
this.logger.debug('disconnect refresh requested, closing old websocket');
this.stateMachine.handle('server disconnect old socket');
// TODO: instead of using this event to reassign secondaryWebsocket to this.websocket,
// use the websocket close event
return;
}
// Define Ack
const ack = async (response: object): Promise<void> => {
this.logger.debug('calling ack', event.type);
await this.send(event.envelope_id, response);
};
// for events_api messages, expose the type of the event
if (event.type === 'events_api') {
this.emit(event.payload.event.type, { ack, body: event.payload, event: event.payload.event });
} else {
// emit just ack and body for all other types of messages
this.emit(event.type, { ack, body: event.payload });
}
// emitter for all slack events
// used in tools like bolt-js
this.emit('slack_event', { ack, type: event.type, body: event.payload });
}
}
/* Instrumentation */
addAppMetadata({ name: packageJson.name, version: packageJson.version });
export default SocketModeClient;
/*
* Exported types
*/
export interface SocketModeOptions {
appToken?: string; // app level token
logger?: Logger;
logLevel?: LogLevel;
autoReconnectEnabled?: boolean;
clientPingTimeout?: number;
clientOptions?: Omit<WebClientOptions, 'logLevel' | 'logger'>;
}
// NOTE: there may be a better way to add metadata to an error about being "unrecoverable" than to keep an
// independent enum, probably a Set (this isn't used as a type).
enum UnrecoverableSocketModeStartError {
NotAuthed = 'not_authed',
InvalidAuth = 'invalid_auth',
AccountInactive = 'account_inactive',
UserRemovedFromTeam = 'user_removed_from_team',
TeamDisabled = 'team_disabled',
}