What is Backpressure?

Backpressure is a crucial concept in stream management, referring to the situation where the writable stream cannot handle the speed at which a readable stream is sending data. Backpressure helps to prevent memory overload and maintain a balanced data flow between the producer (readable stream) and the consumer (writable stream).

How Backpressure Works in Node.js

In Node.js, streams manage backpressure automatically. If a writable stream cannot write data as quickly as it receives it, the readable stream is paused until the writable stream can process more data.

Example of Backpressure in Streams

Below is an example where a readable stream tries to send data faster than a writable stream can handle.

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In this example, FastReadable produces data very quickly, while SlowWritable simulates a slow writing process. Backpressure is handled automatically, pausing FastReadable when SlowWritable is busy.

Manual Backpressure Control

In addition to automatic handling, you can also manage backpressure manually by checking the return value of the writable stream's write method.

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In this example, customReadable pauses data production if customWritable cannot handle more data (write returns false) and resumes when the drain event is emitted.

Summary

Backpressure is an essential feature for maintaining efficiency and stability in data flow in stream-based systems. Understanding and managing backpressure will allow you to create scalable and efficient applications in Node.js.

Backpressure Diagram