trickle

Simple through stream for Node to slow incoming data to specific intervals, for e.g. when you have to respond to streaming data but obey API rate limits.

For example, the following script will pipe itself to process.stdout, limited to one chunk per second.

var es = require('event-stream')
  , trickle = require('trickle')

var stream = trickle({
    interval: 1000
})

fs.createReadStream(__filename, {
    encoding: 'utf8'
}).pipe(es.split(/\s+/g))
  .pipe(stream)
  .pipe(es.join('\n'))
  .pipe(process.stdout)

If you're looking to throttle data by bytes per second, check out throttle or brake.

Of course, this stream buffers data. If you want to discard input to avoid the stream filling up, use the limit option: this limits the total amount of chunks that the stream will buffer.

By default, the stream will ignore any new data if the buffer is full. Using the mru flag, the stream will instead remove the oldest chunk and add the new one to the end of the queue.

// Emits the most recent recieved chunk
// every second.
trickle({
      mru: true
    , limit: 1
    , interval: 1000
})

// Stores up to 50 chunks, discarding any
// after that. Flushes one chunk every
// five seconds.
trickle({
      limit: 50
    , interval: 5000
})