breeze-dag

Async flow control for directed-acyclic-graph iteration.

Installation

Node.js

breeze-dag is available on npm.

$ npm install breeze-dag

Component

breeze-dag is available as a component.

$ component install qualiancy/breeze-dag

Usage

dag (edges, concurrency, iterator[, done])

• @param {Array} edges
• @param {Number} concurrency
• @param {Function} iterator
• @param {Function} callback

DAG, directed-acyclic-graph, is a graph of nodes in which there are no cyclic references, and therefor has a specific starting and ending point. The dag async method will take an array of edges and resolve a best fit path of execution. It will then iterate over each edge in parallel up to a set amount of threads (concurrency). Furthermore, an edge will not begin it's processing until all of its dependancies have indicated successful execution.

A set of edges is defined as an array, with each element being an array of x, y pairs, where x must complete before y can begin.

var edges = [
    [ 'a', 'b' ]
  , [ 'a', 'c' ]
  , [ 'd', 'e' ]
  , [ 'b', 'd' ]
];

With the above edges, we expect a to start processing. Upon completion, b and c will start. Upon b completion, d will execute, then e.

var dag = require('breeze-dag');

dag(edges, 2, function (e, next) {
  setTimeout(function () {
    next(); // or next(err);
  }, 1000);
}, function (err) {
  // our done callback
  should.not.exist(err);
});

If there are cyclical references in the set of edges, the done callback will be immediately called with an error indicating the problem.

If an error occurs the done callback will be executed immediately. No more items will begin processing, but items that have already started will run to completion.

License

(The MIT License)

Copyright (c) 2012 Jake Luer [email protected] (http://qualiancy.com)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.