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Batcher

Batching your streams since 2012.

Usage

Your logging service takes a stream of JSON objects. You don't want to stream objects as they come, but rather batch them and send them every minute, or when a hundred comes by or some such thing.

var Batcher = require('batcher');

var b = new Batcher({
  batchSize: 100,
  batchTimeMs: 60000,
  encoder: function(items) {
    return items.map(JSON.stringify).join('');
  }
});

b.pipe(net.createConnection(host: 'loggingservice.com', port: 1337));

More frequently, you don't need to pipe it but just accumulate:

b.on('data', function(payload) {
  upload('/somewhere', payload);
});

You can also manually flush the batch:

b.write('one');
b.flush(function() {
  console.log('one has been sent');
});

Batchers support write(), pause(), resume(), flush(), end() and destroy().

pause()/resume() is useful when you need to send with retries, but want to avoid the thundering herd when the server comes back online.

var b = new Batcher({
  batchSize: 1,
  maxBatchSize: 100,
  encoder: function(items) {
    b.pause();

    function send() {
      request({
        url: some_url,
        json: items,
      }, function(err) {
        if (err) return setTimeout(send, 1000);
        b.resume();
      });
    }

    send();
  }
});

batchSize of 1 means send them as they come. maxBatchSize of 100 means if there are more available, send as many as 100. setTimeout is used to retry sending every second.