Notification API WebSocket Reconnection Logic in Node.js

NICE CXone API & Integrations
1

Trying to understand why my Node.js client drops the subscription when reconnecting after a network blip. I am using ws to hit /api/v2/analytics/events, and upon close, I immediately attempt to re-establish the socket. However, I receive a 400 Bad Request because the server expects a Since parameter for the new session. Is there a specific sequence required to resume the stream without missing events?

2

you need to rethink your reconnection strategy because the /api/v2/analytics/events endpoint is stateful regarding the subscription context, not just the websocket connection. when the socket drops, the server-side subscription might still be active, but your client has lost the since timestamp required to resume without gaps or duplicates.

in my aws glue etl jobs, i handle this by maintaining a persistent offset in s3. for a real-time node client, you must store the last processed event.timestamp locally. do not just reconnect blindly.

first, on close, capture the current time or the last known event time. second, when initiating the new websocket connection, you must append the since query parameter formatted as iso 8601. without this, the server defaults to ‘now’, causing you to miss events that occurred during the blip, or it rejects the request if the subscription context is stale.

here is how i structure the reconnect logic in node:

let lastTimestamp = new Date().toISOString();

function connectWebSocket() {
 const sinceParam = new URLSearchParams({ since: lastTimestamp });
 const ws = new WebSocket(`wss://api.genesys.cloud/api/v2/analytics/events?${sinceParam}`, {
 headers: { 'Authorization': `Bearer ${accessToken}` }
 });

 ws.on('message', (data) => {
 const events = JSON.parse(data);
 events.forEach(evt => {
 // process event
 if (new Date(evt.timestamp) > new Date(lastTimestamp)) {
 lastTimestamp = evt.timestamp;
 }
 });
 });

 ws.on('close', () => {
 console.log('connection closed, reconnecting in 1s...');
 setTimeout(connectWebSocket, 1000);
 });
}

this ensures continuity. also, verify your oauth token hasn’t expired during the disconnect. if it has, refresh before opening the new socket. the 400 error often masks a missing or malformed since parameter.

3

If I remember right, the Since parameter is mandatory for resume logic. My gateway stores the last eventTimestamp in Redis.

  1. On reconnect, fetch the latest timestamp.
  2. Append ?since=<timestamp> to /api/v2/analytics/events.
const ws = new WebSocket(`wss://api.mypurecloud.com/api/v2/analytics/events?since=${lastTs}`);

This prevents the 400 Bad Request and ensures DataLoader batching remains consistent.