3.1.1 • Public • Published

non-blocking synchronization(nbs:) in nodejs

RECOMENDED: use fibext instead. domain is optional for your own choice

I do not like Promise, yes I promise. This package is extended from fibers and domain, with much more friendly api(run/wait/resume), much more stronger error handling, much more tolerable for nested run, and aslo working in sync-callback.


  • use run/wait/resume to archive fiber functionality, avoid callback hell
  • without explicit reference to call wait and resume
  • strong error handle and subsequent error handle for any scene, like thrown in sync/async callback, thrown before resume
  • tolerable nested run, no matter whether you call resume in n-th callback, run another fiber stack in async mode, or even wait another fiber stack paused!
  • using pair.resume and pair.wait for a synchronous callback is ok!
  • supply express middleware to wrap every request
  • use nbs.wrap to wrap the node core module's async function run as 'sync' style, like var data = fs.readFile(xxx)


npm install --save nbs

Simple usage

var nbs = require('../index'), wait = nbs.wait, resume = nbs.resume;
var fs = nbs.wrap(require('fs'));//wrap the node module
  var fileContent = fs.readFile('xxx');//it will return the file data directly
  nbs.sleep(1000);//sleep 1s
  //return value from the callback
    resume(null, 'wake up');
  }, 1000);
  console.log(wait());//wake up

Used with express

app.use(nbs.express());//error will be redirected to error middleware
app.get('/sleep', function(req, resp){
  resp.send('wake up').end();

with custom error handling:

  //custom error handler
  onError: function(err, req, resp){
  //if supplied, then the subsequent error will be caught by this listener
  onSubError: function(err){
    console.log('caught subsequent error');
app.get('/sleep', function(req, resp){
  resp.send('wake up').end();

Run with synchronous callback

function funcWithSyncCallback(cb){
  var pair = nbs.pair();
  pair.wait();//will not hung here!

Parallel the async

function get(url, cb){//get the response data from url
  //cb(err, data)
  get('url1', resume);
  get('url2', resume);
  get('url3', resume);
  //data1 may not be the url1's result! it can be url2/url3's result too. 
  //you should not rely on that. same to data2/data3
  var data1 = wait();
  var data2 = wait();
  var data3 = wait();
  console.log(data1, data2, data3);

More usages!

Please refer to the test cases to get more usage examples, like configuration, error handling, nested run, parallel run, etc.



set the global configuration. options has:

  • onError: function(err). the error handler. defaut handler will emit process's uncaughtException event if there is listener at this event or it will crash the process(domain's behavior).
  • onSubError: function(err). the subsequenct error handler. default is null. if you supplied one, then the subsequent error from the nbs will be caught by it. subsequent errors are mainly caused by the async jobs.


reset the global config.

nbs.run(func, [emitter1, emitter2, ...], [errorHandler], [subErrorHandler])

create a nbs-fiber stack, make the func to run in this stack, and any error thrown in this func and its async callbacks will be caught!

  • func: the target function that its subsequent call chain need to be run as-like 'sync'
  • emitterN: you can put the event emitters into this nbs to catch their error. see domain.bind
  • errorHandler: error handler only used by this nbs-fiber stack
  • subErrorHandler: subsequenct error handler only used by this nbs-fiber stack

nbs.wait([param1, param2, ...])

pause the nbs-fiber stack. wait should be used with resume and they must be in pairs. the params will be returned by the next-pair's resume method. wait will return the pair resume's params, and assume that the first param is error or null. if it's error, then throw it. if not, then return the remain parts of the resume params. if the resume params's length = 2, then return the second param to adapt node-style callback. see:

  resume(null, 'a');
wait();//return 'a'
  resume(null, 'a', 'b');
wait();//return ['a', 'b']
  resume(new Error('xxx'));
wait();//throw the error
//adapt to node-style callback
var fileContent = wait(fs.readFile('xxx', resume));


same as nbs.wait(). the difference is waitF will return the pair resume's full params.

waitF();//return 'a'
  resume('a', 'b');
waitF();//return ['a', 'b']

nbs.resume([param1, param2, ...])

resume the paused nbs-fiber stack. the params will be returned by this-pair's wait method; if the first param is an Error, then the pair wait method will throw the error, same to the first param is arguments object and the arguments's first param is an Error.


check whether current stack is in the nbs-fiber stack


sleep the current stack with the specified miliseconds. same as wait(setTimeout(resume, ms)).


express middleware. if you put it in express, then the domain-middleware is not needed anymore. options has:

  • onError: function(err, req, resp). default handler will redirect the error to the next error middleware of express
  • onSubError: function(err). there is no req and resp in the function. it's useful to record the subsequenct error.

nbs.wrap(functionOrObject, [deepTheFunction])

wrap node-style async functions to instead run in 'sync' style and return the value directly. this assumes that the last parameter of the function is async callback.

if a single function is passed then a wrapped function is created. if an object is passed then a new object is returned with all functions wrapped.

there is no way to get the underlying function's return. if you need, please use the unwrapped ones, such as child_process.execFile's return child.

and you should not call the sync-style function from the wrap, like readFileSync, they will block the fiber stack. use underscore.pick or _.omit to omit the sync-style functions.

var readFile = nbs.wrap(require('fs').readFile);
var fs = nbs.wrap(_.pick(require('fs'), 'readFile', 'writeFile'));
var request = nbs.wrap(require('request'), true);//wrap request and request.get ...
var fileContent = readFile('example.txt');
var fileContent = fs.readFile('example.txt');


run command npm run test-cov .

=============================== Coverage summary ===============================
Statements   : 98.08% ( 204/208 )
Branches     : 93.46% ( 100/107 )
Functions    : 100% ( 35/35 )
Lines        : 98.92% ( 183/185 )

Benchmark with cps

run command npm run bench to compare the setTimeout(fn, 0) operation

cps: 64.55777921239509 op/s 15.49 ms/op
nbs: 64.76683937823834 op/s 15.44 ms/op

License :

Licensed under MIT

Copyright (c) 2015 kiliwalk

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