warning: possible EventEmitter memory leak detected

The warning is triggered from gulpfile.js in rebundle, with listener registration shown in factor-bundle/index.js. Start by tracing the repeated bundler.plugin('factor-bundle') calls in the supplied watchify setup and reproduce several rebundles. Done means repeated rebundles no longer produce the EventEmitter warning while the shared and per-file outputs are still generated.

I am using factor-bundle with watchify and gulp.

var gulp = require('gulp');
var gutil = require('gulp-util');
var source = require('vinyl-source-stream');
var browserify = require('browserify');
var reactify = require('reactify');
var watchify = require('watchify');
var factor = require('factor-bundle');
var uglify = require('gulp-uglify');
var fs = require('fs');
var concat = require('concat-stream');
var file = require('gulp-file');

gulp.task('watch', bundle)

function bundle () {

  // react components
  var files = [
    '/path/to/file1.jsx',
    '/path/to/file2.jsx',
    '/path/to/file3.jsx'
  ];


  var bundler = watchify(browserify(watchify.args)) 

  bundler.add(files);
  bundler.add('./lib/api.js', {expose: 'api'});
  bundler.require('./lib/api.js', {expose: 'api'});
  bundler.transform('reactify');
  bundler.on('update', rebundle);

  function rebundle() {
    bundler.plugin('factor-bundle', {
        outputs: [
          write('/path/to/file1.js'),
          write('/path/to/file2.js'),
          write('/path/to/file3.js'),
          ]
    });
    bundler.bundle()
        .on('error', gutil.log.bind(gutil, 'Browserify Error'))
        .pipe(write('shared.js'));
  };

  return rebundle();
}


function write (name) {
    return concat(function (content) {
        // create new vinyl file from content and use the basename of the
        // filepath in scope as its basename.
        return file(name, content, { src: true })
        // uglify content
        .pipe(uglify())
        // write content to build directory
        .pipe(gulp.dest('./public/bundles/'))
    });
}

It works fine but after five or ten rebundles I start seeing the following warning:

Trace
    at Browserify.addListener (events.js:179:15)
    at f (/Users/benoit/git/figure/web/node_modules/factor-bundle/index.js:55:7)
    at Browserify.plugin (/Users/benoit/git/figure/web/node_modules/browserify/index.js:345:9)
    at Browserify.bundle (/Users/benoit/git/figure/web/gulpfile.js:46:13)
    at Browserify.emit (events.js:107:17)
    at null._onTimeout (/Users/benoit/git/figure/web/node_modules/watchify/index.js:126:15)
    at Timer.listOnTimeout (timers.js:110:15)
(node) warning: possible EventEmitter memory leak detected. 11 finish listeners added. Use emitter.setMaxListeners() to increase limit.
Trace
    at ConcatStream.addListener (events.js:179:15)
    at ConcatStream.once (events.js:204:8)
    at Labeled.Readable.pipe (/Users/benoit/git/figure/web/node_modules/factor-bundle/node_modules/labeled-stream-splicer/node_modules/stream-splicer/node_modules/readable-stream/lib/_stream_readable.js:612:8)
    at /Users/benoit/git/figure/web/node_modules/factor-bundle/index.js:73:43
    at Array.reduce (native)
    at Transform._flush (/Users/benoit/git/figure/web/node_modules/factor-bundle/index.js:65:35)
    at Transform.<anonymous> (/Users/benoit/git/figure/web/node_modules/factor-bundle/node_modules/through2/node_modules/readable-stream/lib/_stream_transform.js:135:12)
    at Transform.g (events.js:199:16)
    at Transform.emit (events.js:129:20)
    at finishMaybe (/Users/benoit/git/figure/web/node_modules/factor-bundle/node_modules/through2/node_modules/readable-stream/lib/_stream_writable.js:371:12)
    at endWritable (/Users/benoit/git/figure/web/node_modules/factor-bundle/node_modules/through2/node_modules/readable-stream/lib/_stream_writable.js:378:3)
    at Transform.Writable.end (/Users/benoit/git/figure/web/node_modules/factor-bundle/node_modules/through2/node_modules/readable-stream/lib/_stream_writable.js:356:5)
(node) warning: possible EventEmitter memory leak detected. 11 finish listeners added. Use emitter.setMaxListeners() to increase limit.