noflo

NoFlo: Flow-based programming for JavaScript

NoFlo is an implementation of flow-based programming for JavaScript running on both Node.js and the browser. From WikiPedia:

In computer science, flow-based programming (FBP) is a programming paradigm that defines applications as networks of "black box" processes, which exchange data across predefined connections by message passing, where the connections are specified externally to the processes. These black box processes can be reconnected endlessly to form different applications without having to be changed internally. FBP is thus naturally component-oriented.

Developers used to the Unix philosophy should be immediately familiar with FBP:

This is the Unix philosophy: Write programs that do one thing and do it well. Write programs to work together. Write programs to handle text streams, because that is a universal interface.

It also fits well in Alan Kay's original idea of object-oriented programming:

I thought of objects being like biological cells and/or individual computers on a network, only able to communicate with messages (so messaging came at the very beginning -- it took a while to see how to do messaging in a programming language efficiently enough to be useful).

NoFlo has been written in CoffeeScript for simplicity. The system is heavily inspired by J. Paul Morrison's book Flow-Based Programming.

Read more at http://noflojs.org/.

Requirements and installing

NoFlo is available for Node.js via NPM, so you can install it with:

$ npm install -g noflo

You can customize and download the browser version of NoFlo at http://noflojs.org/download/.

Installing from Git

NoFlo requires a reasonably recent version of Node.js, and some npm packages. Ensure you have the grunt-cli package installed (grunt command should be available on command line) and NoFlo checked out from Git. Build NoFlo with:

$ grunt build

You can also build NoFlo only for the desired target platform with either grunt build:nodejs or grunt build:browser.

Then you can install everything needed by a simple:

$ npm link

NoFlo is available from GitHub under the MIT license.

Changes

Please refer to the Release Notes and the CHANGES.md document.

Usage

Please refer to http://noflojs.org/documentation/.

Development

NoFlo development happens on GitHub. Just fork the main repository, make modifications and send a pull request.

We have an extensive suite of tests available for NoFlo. Run them with:

$ grunt test

or:

$ npm test

Platform-specific tests

By default, the tests are run for both Node.js and the browser. You can also run only the tests for a particular target platform:

$ grunt test:nodejs

or:

$ grunt test:browser

Running tests automatically

The build system used for NoFlo is also able to watch for changes in the filesystem and run the tests automatically when something changes. To start the watcher, run:

$ grunt watch

To quit thew watcher, just end the process with Ctrl-C.

Discussion

Flow-based programming in general, including NoFlo can be discussed on the Flow Based Programming Google group.

There is also an IRC channel #fbp on FreeNode.

Changelog

0.5.0 (March 28th 2014)

• Support for setting the default baseDir of Node.js NoFlo environment with NOFLO_PROJECT_ROOT env var (defaults to current working directory)
• Support for loading graph definitions via AJAX on browser-based NoFlo
• Support for delayed initialization of Subgraph components via ComponentLoader
• Component instances now get the node's metadata passed to the getComponent function
• New methods for manipulating Graph metadata:
  • setProperties
  • setInportMetadata
  • setOutportMetadata
  • setGroupMetadata
  • setNodeMetadata
  • setEdgeMetadata
• Graph exports can now be renamed, and emit addExport, removeExport, and renameExport events
• New Graph transaction API for grouping graph changes. Transactions can be observed
  • startTransaction
  • endTransaction
• New Journal class, for following Graph changes and restoring earlier revisions. Currently supports undo and redo
• New port API allowing better addressability and metadata
• Graph's published ports are now declared in two separate inports and outports arrays to reduce ambiguity

With the new API component ports can be declared with:

@inPorts = new noflo.InPorts
@inPorts.add 'in', new noflo.InPort
  datatype: 'object'
  type: 'http://schema.org/Person'
  description: 'Persons to be processed'
  required: true
  buffered: true

The noflo.Ports objects emit add and remove events when ports change. They also support passing port information as options:

@outPorts = new noflo.OutPorts
  out: new noflo.OutPort
    datatype: 'object'
    type: 'http://schema.org/Person'
    description: 'Processed person objects'
    required: true
    addressable: true

The input ports also allow passing in an optional processing function that gets called on information packets events.

• New component API allowing simpler component definition in both CoffeeScript and JavaScript:

var noflo = require('noflo');

exports.getComponent = function() {
  var c = new noflo.Component();

  c.inPorts.add('in', function(event, payload) {
    if (packet.event !== 'data')
      return;
    // Do something with the packet, then
    c.outPorts.out.send(packet.data);
  });

  c.outPorts.add('out');

  return c;
};

• Support for dealing with component source code via ComponentLoader setSource and getSource methods