Polling as fallback in Flask - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is polling in web applications?

Polling is a technique where the client repeatedly asks the server for updates at regular intervals.

beginner

Why use polling as a fallback in Flask apps?

Polling is used as a fallback when real-time communication methods like WebSockets are not supported or fail, ensuring the client still receives updates.

intermediate

How does polling work in a Flask app?

The client sends repeated HTTP requests to a Flask route that returns the latest data. The client waits a set time between requests.

intermediate

What is a downside of polling compared to WebSockets?

Polling can cause more network traffic and latency because it sends requests even when no new data is available.

intermediate

How can you implement polling in a Flask frontend?

Use JavaScript's setInterval to send fetch requests to a Flask endpoint periodically and update the page with the response.

What does polling do in a Flask web app?

A Keeps a permanent connection open

B Pushes data from server to client automatically

C Repeatedly requests data from the server

D Blocks the server until data changes

Polling means the client asks the server repeatedly for updates.

Why might polling be used as a fallback?

A Because WebSockets might not be supported

B Because polling is faster than WebSockets

C Because polling uses less network traffic

D Because polling requires no client code

Polling is a fallback when real-time methods like WebSockets are unavailable.

Which JavaScript function is commonly used to implement polling?

A clearInterval

B setInterval

C setTimeout

D addEventListener

setInterval runs code repeatedly at fixed time intervals, perfect for polling.

What is a disadvantage of polling?

A It blocks the browser UI

B It requires a WebSocket server

C It only works on mobile devices

D It can cause unnecessary network requests

Polling sends requests even if no new data is available, causing extra traffic.

In Flask, polling endpoints usually return what type of data?

A JSON with the latest updates

B HTML pages only

C Binary files

D CSS stylesheets

Polling endpoints typically return JSON data for easy client updates.

Explain how polling works as a fallback method in a Flask web application.

Think about how the client keeps asking the server for updates.

Describe the pros and cons of using polling compared to WebSockets in Flask apps.

Consider speed, network use, and compatibility.