CODEWITHSUNDEEP
node.jsstream
Brad
Brad

Reputation: 163232

How does stream backpressure behave with multiple stream listeners?

Suppose I have a readable stream, sourceStream, that generates ~32KB of data every second. I want to pipe this data to the writable streams of multiple HTTP clients.

Client A has a great internet connection and can keep up with my stream data. Client B is connected on his/her trusty 14.4kbps US Robotics modem.

sourceStream.pipe(resClientA); // Pipe to Client A's writable stream
sourceStream.pipe(resClientB); // Pipe to Client B's writable stream

These are TCP connections and Node.js is going to be able to know when a client is getting behind. I know that there is a small amount of buffering built into Streams, but it won't be long before that buffer is full and Node.js will have to do something with all that data being produced by sourceStream.

Will it buffer indefinitely for Client B while Client A continues to get data as expected? Or, will Node pause the stream until Client B can catch up, meaning that this stream is paused for Client A as well? Or, will something else happen?

Upvotes: 4

Views: 822

Answers (1)

Jonathan Ong
Jonathan Ong

Reputation: 20315

It goes as slow as the slowest reader. Source: https://github.com/isaacs/stream-multiplexer#the-problem

Most of the time, you'd prefer that the reader goes no faster than the slowest writer can accomodate. In Node v0.10, this is how it works.

Upvotes: 5

Related Questions