Long polling as fallback in Node.js - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is long polling in web communication?

Long polling is a technique where the client sends a request to the server and the server holds the request open until new data is available or a timeout occurs. Then the server responds, and the client immediately sends another request to wait for more data.

beginner

Why use long polling as a fallback method?

Long polling is used as a fallback when real-time communication methods like WebSockets are not supported by the client or network. It simulates real-time updates by repeatedly requesting data from the server.

intermediate

How does long polling differ from regular polling?

Regular polling sends requests at fixed intervals regardless of data availability, which can waste resources. Long polling keeps the request open until data is ready, reducing unnecessary requests and improving efficiency.

intermediate

In Node.js, what is a key consideration when implementing long polling?

You must manage open connections carefully to avoid blocking the event loop. Using asynchronous callbacks and proper timeout handling ensures the server remains responsive while holding requests open.

beginner

What happens on the client side after receiving a response from a long polling request?

The client processes the received data and immediately sends a new long polling request to the server to wait for the next update, maintaining a continuous connection-like experience.

What does long polling do differently compared to regular polling?

A Keeps the request open until data is available or timeout

B Sends requests at fixed intervals regardless of data

C Uses WebSocket protocol for communication

D Closes connection immediately after sending request

Long polling holds the request open until new data is ready or a timeout occurs, unlike regular polling which sends requests at fixed intervals.

Why might long polling be used as a fallback method?

A Because it requires no client requests

B Because it is faster than WebSockets

C Because it uses less server memory than WebSockets

D Because WebSockets are not supported or blocked

Long polling is used when WebSockets are not supported or blocked by the client or network.

In Node.js, what should you avoid when implementing long polling?

A Blocking the event loop with synchronous code

B Using asynchronous callbacks

C Setting timeouts for requests

D Sending multiple requests from the client

Blocking the event loop with synchronous code can make the server unresponsive during long polling.

What does the client do after receiving data from a long polling response?

A Waits for a fixed time before sending another request

B Closes the connection and stops requests

C Sends a new long polling request immediately

D Switches to WebSocket communication

The client immediately sends a new long polling request to keep waiting for updates.

Which of these is NOT a benefit of long polling?

A Reduces unnecessary requests compared to regular polling

B Uses less bandwidth than WebSockets

C Simulates real-time updates without WebSockets

D Works in environments where WebSockets are blocked

Long polling generally uses more bandwidth than WebSockets because it repeatedly opens and closes HTTP connections.

Explain how long polling works as a fallback method for real-time communication.

Think about how the client and server keep talking without WebSockets.

Describe key considerations when implementing long polling in Node.js.

Focus on how Node.js handles many requests at once.