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

0.5.1 (May 8th 2014)

• Custom component loaders can be registered programmatically using the registerLoader method of NoFlo's ComponentLoader
• contains method for buffered inports returns the number of data packets the buffer has
• Call stack exhaustion on very large graphs has been fixed
• The error outport of AsyncComponents now sends the group information of the original input together with the error
• The error method of regular ports can now also handle groups as a second parameter
• Ports can now list their attached sockets (by array index) via the listAttached method
• function is now an accepted datatype for ports
• There is now initial support for making connections to and from addressable ports with a specified index

In the FBP format, these can be specified with the bracket syntax:

SomeNode OUT[2] -> IN OtherNode
'foo' -> OPTS[1] OtherNode

In the JSON file these are defined in connections by adding a integer to the index key of the src or tgt definition.

The NoFlo Graph class provides these with the following methods:

addEdgeIndex(str outNode, str outPort, int outIndex, str inNode, str inPort, int inIndex, obj metadata)
addInitiaIndex(mixed data, str inNode, str inPort, int inIndex, obj metadata)

If indexes are not specified, the fall-back behavior is to automatically index the connections based on next available slot in the port.