Asynchronous message bus (UI16)
UI16 uses Asynchronous message bus architecture developed by ServiceNow in Geneva release. Traditionally, browsers (client) used a concept of “Short Polling” to retrieve data from Server (ServiceNow). AMB however uses “Long polling” concept to retrieve data.
The two approaches are explained here:
- Short Polling: Here, client continuously sends polling request to server at a defined short time and server pushes the updates (events) back to client as a response. A simple diagram illustrates the approach. This means this is a synchronous approach which might lead to performance issues since the client regularly sends request to server even if there are no changes happened.
Consequences are that if the polling interval is increased, data freshness might be affected and if the interval is reduced, performance issues might occur.
- Long Polling: Here, client sends initial request to server and then sits back idle until the server reponds to the intial request on some event occurred. As soon as the server responds, the client sends a new request and the process goes on.
In short, Long polling is an efficient mechanism in which browser triggers a request to instance & the instance listens for changes in real time notifies the browser in an asynchronous way.
Some functionalities which uses this architecture are Live updates to forms, Service portal, VTB, Connect Chat
