Server polling with JavaScript

Question

What are some good practices for polling a server with JavaScript for an application that needs to refresh data very rapidly? I'm using jQuery for front-end and Java Spring Framework for backend.

Example of refreshed data could be list of items that are getting updated very rapidly (every 1 second).

Answer 1

You may want to use jQuery's Ajax functions to poll the server every second or so. Then the server can respond with instructions to the browser in near real-time.

You can also consider long polling instead of the above, to reduce the latency without increasing the frequency of the polls.

Quoting Comet Daily: The Long-Polling Technique:

The long-polling Comet technique is a technique that optimizes traditional polling to reduce latency.

Traditional polling sends an XMLHttpRequest to the server in fixed intervals. For example, open a new XMLHttpRequest every 15 seconds, receive an immediate response, and close the connection.

Long-polling sends a request to the server, but a response is not returned to the client until one is available. As soon as the connection is closed, either due to a response being received by the client or if a request times out, a new connection is initiated. The result is a significant reduction in latency because the server usually has a connection established when it is ready to return information to return to the client.

In addition to the above, I also suggest that you check out the accepted answer to the following Stack Overflow post for a detailed description of the long polling technique:

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