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Long Polling vs Short Polling

Understanding the differences between long polling and short polling is crucial in the context of real-time data fetching and server-client communication in web development. Both are techniques used to periodically check for updates, but they differ significantly in how they operate.

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Long Polling​

Overview​

  • Long Polling is a variation of the traditional polling technique where the server holds a client request open until new data is available.
  • Upon receiving new data, the server responds and closes the connection. The client then immediately sends another request, thus creating a near-continuous connection.

Key Features​

  • Reduced Latency: Delivers updates with minimal delay.
  • Server-Triggered Responses: Server sends data as soon as it's available.
  • Efficient for Real-Time Data: Ideal for applications requiring real-time updates.

Use Cases​

  • Chat Applications: Delivers messages in real-time.
  • Live Sports Updates: Instantly updates scores and events.
  • Notification Systems: Alerts users to new events or changes immediately.

Short Polling​

Overview​

  • Short Polling involves the client sending HTTP requests at regular intervals to check for updates.
  • The server processes each request and returns a response immediately, regardless of whether new data is available.

Key Features​

  • Simple Implementation: Easier to implement than long polling.
  • High Frequency Polling: Can be set to poll at very short intervals.
  • Independent Requests: Each request is independent, reducing server memory usage.

Use Cases​

  • Periodic Data Updates: Useful for data that changes at predictable intervals.
  • System Health Checks: Regularly checks the status of systems or services.
  • Content Feeds: Updates feeds where real-time data is not critical.

Key Differences​

  1. Connection Duration: Long polling holds the connection open, while short polling involves repeated separate requests.
  2. Data Latency: Long polling provides data with lower latency compared to short polling.
  3. Server Load: Long polling can be more demanding on the server, especially with many open connections.
  4. Implementation Complexity: Long polling is generally more complex to implement than short polling.
  5. Real-Time Capability: Long polling is better suited for real-time applications.

In conclusion, the choice between long polling and short polling depends on the specific requirements of your application, particularly in terms of real-time data needs and server capabilities.