Implementing WebSocket Reconnection Logic for the Genesys Cloud Notification API in Node.js

What You Will Build

• A robust WebSocket client in Node.js that subscribes to real-time events from Genesys Cloud.
• Implementation of exponential backoff and jitter for automatic reconnection during network or server-side interruptions.
• Handling of authentication expiration and seamless token refresh without dropping the subscription stream.

Prerequisites

• OAuth Client Type: Confidential Client (Client Credentials Grant) or Public Client (Authorization Code Grant with PKCE). For this tutorial, we assume a Confidential Client running in a server environment.
• Required Scopes: analytics:call:center:read, routing:conversation:view, or user:presence:read depending on the event type. The Notification API itself requires no specific scope to connect, but the events you receive require scopes on the associated entities.
• SDK/API Version: Genesys Cloud REST API v2. We will use raw ws library instead of the SDK for the WebSocket layer, as the SDK’s WebSocket support is often better handled via direct implementation for custom reconnection logic.
• Runtime: Node.js v18 or later.
• Dependencies:
  • ws (WebSocket client)
  • axios (For OAuth token retrieval)
  • uuid (For generating unique subscription IDs)

Authentication Setup

The Genesys Cloud Notification API requires a valid OAuth 2.0 access token in the WebSocket handshake headers. Unlike HTTP REST calls, WebSocket handooks do not support standard Authorization: Bearer <token> headers in all client implementations. Genesys Cloud accepts the token in the Authorization header of the WebSocket upgrade request.

Because tokens expire (typically every hour), your client must handle token refresh. If the token expires while the WebSocket is open, Genesys Cloud will close the connection with a specific close code. Your reconnection logic must detect this, fetch a new token, and reconnect.

import axios from 'axios';

const GENESYS_REGION = 'my.genesys.cloud'; // e.g., 'usw2', 'euw1'
const CLIENT_ID = process.env.GENESYS_CLIENT_ID;
const CLIENT_SECRET = process.env.GENESYS_CLIENT_SECRET;

/**
 * Fetches a new OAuth2 access token using Client Credentials flow.
 * @returns {Promise<string>} The access token string.
 */
async function getAccessToken() {
  const tokenUrl = `https://${GENESYS_REGION}/oauth/token`;
  const basicAuth = Buffer.from(`${CLIENT_ID}:${CLIENT_SECRET}`).toString('base64');

  try {
    const response = await axios.post(
      tokenUrl,
      new URLSearchParams({ grant_type: 'client_credentials' }),
      {
        headers: {
          'Authorization': `Basic ${basicAuth}`,
          'Content-Type': 'application/x-www-form-urlencoded',
        },
      }
    );

    if (!response.data.access_token) {
      throw new Error('No access_token in response');
    }

    return response.data.access_token;
  } catch (error) {
    console.error('Failed to fetch access token:', error.message);
    throw error;
  }
}

Implementation

Step 1: Define the Notification Subscription Payload

To subscribe to events, you must send a JSON message to the WebSocket immediately after the connection is established. This message defines the type of event (e.g., routing:conversation:updated) and the filter criteria.

The Notification API supports various event types. For this example, we will subscribe to Routing Conversation Updated events, which trigger when a conversation state changes (e.g., queued, answered, held).

import { v4 as uuidv4 } from 'uuid';

/**
 * Constructs the subscription payload for the Notification API.
 * @param {string} token - The current OAuth access token.
 * @returns {object} The JSON payload to send.
 */
function createSubscriptionPayload() {
  // Generate a unique ID for this subscription to help with debugging
  const subscriptionId = uuidv4();

  return {
    id: subscriptionId,
    type: 'routing:conversation:updated', // The event type to listen to
    filter: {
      // Optional: Filter by specific user, queue, or wrapup code
      // Example: { userId: '123e4567-e89b-12d3-a456-426614174000' }
    }
  };
}

Step 2: Implement the WebSocket Client with Reconnection Logic

The core of this tutorial is the NotificationClient class. It manages the WebSocket lifecycle, handles the handshake with the access token, sends the subscription, and implements exponential backoff with jitter for reconnection.

Key behaviors to implement:

1. Handshake: Pass the Authorization header.
2. Subscription: Send the JSON payload upon open.
3. Error Handling: Listen for close events. If the code is 1000 (normal), do not reconnect. If it is 4001 (token expired) or any other error, trigger reconnection.
4. Backoff: Use an exponential backoff strategy (e.g., 1s, 2s, 4s, 8s) with a maximum cap (e.g., 60s) and random jitter to prevent thundering herd problems when the server restarts.

import WebSocket from 'ws';
import { getAccessToken } from './auth.js'; // Assume auth.js from Step 1
import { createSubscriptionPayload } from './subscription.js'; // Assume subscription.js from Step 1

class NotificationClient {
  constructor(region, options = {}) {
    this.region = region;
    this.wsUrl = `wss://${region}/api/v2/analytics/events`; // Genesys Cloud Notification Endpoint
    this.ws = null;
    this.isRunning = false;
    this.reconnectAttempts = 0;
    this.maxReconnectAttempts = 10;
    this.baseDelay = 1000; // 1 second
    this.maxDelay = 60000; // 60 seconds
    
    // Callbacks for external consumption
    this.onEvent = options.onEvent || (() => {});
    this.onError = options.onError || (console.error);
  }

  /**
   * Starts the WebSocket client with reconnection logic.
   */
  async start() {
    if (this.isRunning) {
      console.warn('Client is already running.');
      return;
    }
    this.isRunning = true;
    await this.connect();
  }

  /**
   * Stops the WebSocket client.
   */
  stop() {
    this.isRunning = false;
    if (this.ws) {
      this.ws.close(1000, 'Client stopped manually');
    }
  }

  /**
   * Establishes the WebSocket connection.
   */
  async connect() {
    if (!this.isRunning) return;

    try {
      // 1. Get a fresh token
      const token = await getAccessToken();
      
      // 2. Prepare headers for the WebSocket handshake
      const headers = {
        'Authorization': `Bearer ${token}`,
        'Content-Type': 'application/json'
      };

      console.log(`Connecting to ${this.wsUrl}... (Attempt ${this.reconnectAttempts + 1})`);

      // 3. Initialize WebSocket
      this.ws = new WebSocket(this.wsUrl, { headers });

      // 4. Attach event listeners
      this.ws.on('open', () => {
        console.log('WebSocket connection established.');
        this.reconnectAttempts = 0; // Reset attempts on successful connection
        this.sendSubscription();
      });

      this.ws.on('message', (data) => {
        this.handleMessage(data);
      });

      this.ws.on('close', (code, reason) => {
        this.handleClose(code, reason);
      });

      this.ws.on('error', (error) => {
        this.handleError(error);
      });

    } catch (error) {
      this.handleError(error);
    }
  }

  /**
   * Sends the subscription payload to Genesys Cloud.
   */
  sendSubscription() {
    if (!this.ws || this.ws.readyState !== WebSocket.OPEN) {
      console.error('Cannot send subscription: WebSocket is not open.');
      return;
    }

    const payload = createSubscriptionPayload();
    console.log('Sending subscription payload:', JSON.stringify(payload));
    this.ws.send(JSON.stringify(payload));
  }

  /**
   * Processes incoming messages.
   * @param {Buffer} data - The raw message data.
   */
  handleMessage(data) {
    try {
      const event = JSON.parse(data.toString());
      
      // Genesys Cloud sends a 'subscription' confirmation message first
      if (event.type === 'subscription') {
        console.log('Subscription confirmed by server:', event.id);
        return;
      }

      // Process actual business events
      this.onEvent(event);
    } catch (error) {
      console.error('Error parsing message:', error);
    }
  }

  /**
   * Handles the close event. Determines if reconnection is necessary.
   * @param {number} code - The WebSocket close code.
   * @param {Buffer} reason - The close reason.
   */
  handleClose(code, reason) {
    console.log(`WebSocket closed. Code: ${code}, Reason: ${reason.toString()}`);

    // 1000 is normal closure. Do not reconnect.
    if (code === 1000) {
      console.log('Normal closure. Stopping client.');
      this.isRunning = false;
      return;
    }

    // 4001 often indicates token expiration or invalid token
    if (code === 4001) {
      console.warn('Token expired or invalid. Reconnecting with new token...');
      this.reconnect();
      return;
    }

    // For any other unexpected closure, attempt to reconnect
    if (this.isRunning) {
      console.warn('Unexpected closure. Reconnecting...');
      this.reconnect();
    }
  }

  /**
   * Handles WebSocket errors.
   * @param {Error} error - The error object.
   */
  handleError(error) {
    console.error('WebSocket error:', error.message);
    this.onError(error);
    
    // If the client is still supposed to be running, trigger reconnection
    if (this.isRunning) {
      this.reconnect();
    }
  }

  /**
   * Implements exponential backoff with jitter for reconnection.
   */
  reconnect() {
    if (!this.isRunning) return;

    this.reconnectAttempts++;

    if (this.reconnectAttempts > this.maxReconnectAttempts) {
      console.error(`Max reconnection attempts (${this.maxReconnectAttempts}) reached. Giving up.`);
      this.isRunning = false;
      return;
    }

    // Calculate delay: min(maxDelay, baseDelay * 2^attempt)
    const exponentialDelay = Math.min(this.baseDelay * Math.pow(2, this.reconnectAttempts), this.maxDelay);
    
    // Add jitter: random value between 0 and 1000ms
    const jitter = Math.random() * 1000;
    const delay = exponentialDelay + jitter;

    console.log(`Reconnecting in ${Math.round(delay)}ms...`);

    setTimeout(() => {
      this.connect();
    }, delay);
  }
}

export { NotificationClient };

Step 3: Processing Results and Edge Cases

When the WebSocket receives data, it is a JSON string. You must parse it. The first message you will receive after sending your subscription is a subscription event from Genesys Cloud confirming that your filter is active. Subsequent messages are the actual data events.

It is critical to handle the subscription message separately so you do not process it as business data.

Edge cases to consider:

1. Rate Limiting: If you subscribe to too many events or filters, Genesys Cloud may throttle you. The WebSocket will not necessarily close, but you may stop receiving events. Check the status field in the subscription confirmation.
2. Payload Size: Large payloads can cause memory issues if not processed quickly. Ensure your onEvent callback is asynchronous or offloads processing to a queue.
3. Timeouts: If the server does not respond to the subscription request within a reasonable time, the connection might hang. Implement a timeout for the initial subscription confirmation.

// Example usage of the NotificationClient

const { NotificationClient } = await import('./NotificationClient.js');

const client = new NotificationClient('my.genesys.cloud', {
  onEvent: (event) => {
    console.log('Received Event:', JSON.stringify(event, null, 2));
    
    // Example: Filter for specific conversation states
    if (event.type === 'routing:conversation:updated') {
      const state = event.data?.state;
      if (state === 'queued') {
        console.log(`Conversation ${event.data?.id} is now queued.`);
      } else if (state === 'answered') {
        console.log(`Conversation ${event.data?.id} has been answered.`);
      }
    }
  },
  onError: (error) => {
    console.error('Critical Error:', error);
    // In a production app, you might want to alert ops here
  }
});

// Handle graceful shutdown
process.on('SIGINT', () => {
  console.log('Shutting down...');
  client.stop();
  process.exit(0);
});

// Start the client
client.start().catch(console.error);

Complete Working Example

Below is the complete, copy-pasteable index.js file. It combines authentication, subscription logic, and the reconnection client into a single module for ease of testing.

import axios from 'axios';
import WebSocket from 'ws';
import { v4 as uuidv4 } from 'uuid';

// Configuration
const GENESYS_REGION = process.env.GENESYS_REGION || 'my.genesys.cloud';
const CLIENT_ID = process.env.GENESYS_CLIENT_ID;
const CLIENT_SECRET = process.env.GENESYS_CLIENT_SECRET;

if (!CLIENT_ID || !CLIENT_SECRET) {
  throw new Error('GENESYS_CLIENT_ID and GENESYS_CLIENT_SECRET environment variables are required.');
}

/**
 * Fetches a new OAuth2 access token.
 */
async function getAccessToken() {
  const tokenUrl = `https://${GENESYS_REGION}/oauth/token`;
  const basicAuth = Buffer.from(`${CLIENT_ID}:${CLIENT_SECRET}`).toString('base64');

  const response = await axios.post(
    tokenUrl,
    new URLSearchParams({ grant_type: 'client_credentials' }),
    {
      headers: {
        'Authorization': `Basic ${basicAuth}`,
        'Content-Type': 'application/x-www-form-urlencoded',
      },
    }
  );

  return response.data.access_token;
}

/**
 * Genesys Cloud Notification Client with Reconnection Logic
 */
class GenesysNotificationClient {
  constructor(region) {
    this.region = region;
    this.wsUrl = `wss://${region}/api/v2/analytics/events`;
    this.ws = null;
    this.isRunning = false;
    this.reconnectAttempts = 0;
    this.maxReconnectAttempts = 10;
    this.baseDelay = 1000;
    this.maxDelay = 60000;
  }

  async start() {
    if (this.isRunning) return;
    this.isRunning = true;
    await this.connect();
  }

  stop() {
    this.isRunning = false;
    if (this.ws) {
      this.ws.close(1000, 'Stopped');
    }
  }

  async connect() {
    if (!this.isRunning) return;

    try {
      const token = await getAccessToken();
      const headers = {
        'Authorization': `Bearer ${token}`,
        'Content-Type': 'application/json'
      };

      console.log(`[Attempt ${this.reconnectAttempts + 1}] Connecting to ${this.wsUrl}...`);
      
      this.ws = new WebSocket(this.wsUrl, { headers });

      this.ws.on('open', () => {
        console.log('Connected. Sending subscription...');
        this.reconnectAttempts = 0;
        this.sendSubscription();
      });

      this.ws.on('message', (data) => {
        this.handleMessage(data);
      });

      this.ws.on('close', (code, reason) => {
        this.handleClose(code, reason);
      });

      this.ws.on('error', (error) => {
        this.handleError(error);
      });

    } catch (error) {
      this.handleError(error);
    }
  }

  sendSubscription() {
    if (!this.ws || this.ws.readyState !== WebSocket.OPEN) return;

    const payload = {
      id: uuidv4(),
      type: 'routing:conversation:updated',
      filter: {} // Empty filter means all conversations
    };

    this.ws.send(JSON.stringify(payload));
  }

  handleMessage(data) {
    try {
      const event = JSON.parse(data.toString());
      
      if (event.type === 'subscription') {
        console.log('Subscription confirmed.');
        return;
      }

      // Process business event
      console.log('Event Received:', event.type);
      // Add your business logic here
    } catch (e) {
      console.error('Error parsing event:', e);
    }
  }

  handleClose(code, reason) {
    console.log(`Closed: ${code} - ${reason}`);
    
    if (code === 1000) {
      this.isRunning = false;
      return;
    }

    if (this.isRunning) {
      this.reconnect();
    }
  }

  handleError(error) {
    console.error('Error:', error.message);
    if (this.isRunning) {
      this.reconnect();
    }
  }

  reconnect() {
    if (!this.isRunning) return;

    this.reconnectAttempts++;

    if (this.reconnectAttempts > this.maxReconnectAttempts) {
      console.error('Max retries reached. Stopping.');
      this.isRunning = false;
      return;
    }

    const exponentialDelay = Math.min(this.baseDelay * Math.pow(2, this.reconnectAttempts), this.maxDelay);
    const jitter = Math.random() * 1000;
    const delay = exponentialDelay + jitter;

    console.log(`Reconnecting in ${Math.round(delay)}ms...`);
    setTimeout(() => this.connect(), delay);
  }
}

// Initialize and Start
const client = new GenesysNotificationClient(GENESYS_REGION);

process.on('SIGINT', () => {
  console.log('Shutting down...');
  client.stop();
  process.exit(0);
});

client.start();

Common Errors & Debugging

Error: 401 Unauthorized (WebSocket Close Code 4001)

• What causes it: The access token provided in the handshake header is invalid, expired, or lacks the necessary scopes.
• How to fix it: Ensure your getAccessToken function is called immediately before the WebSocket connection is established. In the code above, getAccessToken() is called inside connect(), ensuring a fresh token is used for every reconnection attempt.
• Code Fix: Verify the Authorization header format is exactly Bearer <token>. Do not include extra spaces.

Error: 403 Forbidden

• What causes it: The OAuth client does not have the required scopes for the event type you are subscribing to. For routing:conversation:updated, you need routing:conversation:view.
• How to fix it: Add the correct scopes to your OAuth application in the Genesys Cloud Admin portal.
• Debugging: Check the scope claim in your JWT token to verify it includes the necessary permissions.

Error: WebSocket Connection Refused / ECONNREFUSED

• What causes it: The WebSocket URL is incorrect, or the region is invalid.
• How to fix it: Ensure the region matches your Genesys Cloud instance (e.g., usw2, euw1, au1). The URL format must be wss://{region}/api/v2/analytics/events.
• Code Check: Verify that GENESYS_REGION is set correctly in environment variables.

Error: Subscription Confirmation Timeout

• What causes it: The server did not respond with a subscription event after you sent the payload. This can happen if the filter is invalid.
• How to fix it: Add a timeout mechanism in the open handler. If no subscription message is received within 10 seconds, close the connection and trigger a reconnection with a different filter or check the filter syntax.

Official References

• Genesys Cloud Notification API Documentation
• Genesys Cloud WebSocket Implementation Guide
• Node.js WebSocket Library (ws)