kanban

Kanban is a node.js control-flow library. As the Japanese methodology, it is pull-based.

npm install kanban
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Kanban

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Kanban is a node.js control-flow library. As the Japanese methodology, it is pull-based.

Rationale

Node.js is all about concurrency: the more, the better. If you use external tools, or slow external services, you might reach a point were more concurrency reduce your throughput. You have to do something, and yet you have no data to decide.

Kanban focus is on recording stats and identifying bottlenecks. Then, it helps you improving your system, by specifying a work-in-progress limit to limit the concurrency of a processing step in your app.

Install

npm install kanban --save

Usage

As in kanban, there is a Board and the processing of Jobs happens in Steps.

First, you must create a new Board:

var kanban = require("kanban");
var board = new kanban.Board();

Then, you define some tasks:

board.defineStep("fast", { wip: 2 }, function (obj, done) {
  console.log("Fast step started for " + obj);
  setTimeout(function () {
    console.log("Fast step done for " + obj);
    done();
  }, 1000);
});
board.defineStep("buffer");
board.defineStep("slow", { wip: 1 }, function (obj, done) {
  console.log("Slow step started for " + obj);
  setTimeout(function () {
    console.log("Slow step done for " + obj);
    done();
  }, 5000);
});

Note that the second and third parameters are optional.

Finally you insert some jobs in the Board:

var print = function (err, job) {
  // job is an instance of the Job class
  console.dir(job); 
};

for (var i = 0; i < 15; i++) {
  board.insert(i, print);
}

You can find more examples in the examples folder.

Errors

The errors are handled in a pure node.js-style callbacks, so you MUST call the callback with the error as the first parameter.

If an error happens, the job is removed from the board and the function you inserted with the job is called.

instance.defineStep("a", function (obj, job, cb) {
  cb(new Error("hello world"));
});

instance.insert({ a: "b" }, function (err) {
  console.log(err)
});

Jumping to a specific step

It is possible to jump to a specific step in the board:

instance.defineStep("a", { wip: 1 }, function (obj, job, cb) {
  job.jumpTo("c");
  cb();
}).defineStep("b", { wip: 1 }, function (obj, cb) {
  cb(new Error("hello world"));
}).defineStep("c").defineStep("d", function (obj, cb) {
  cb();
});

instance.insert({ a: "b" }, function (err) {
  console.log(err)
});

Timeouts

It is possible to specify a timeout for a given step, in milliseconds.

If a timeout happens, the job is removed from the board and the function you inserted with the job is called.

// define a timeout of a minute
instance.defineStep("a", { timeout: 60 * 1000 }, function (obj, job, cb) {
  // this function is stuck somewhere, it will not complete
});

instance.insert({ a: "b" }, function (err) {
  console.log(err)
});

Contributing to Kanban

  • Check out the latest master to make sure the feature hasn't been implemented or the bug hasn't been fixed yet
  • Check out the issue tracker to make sure someone already hasn't requested it and/or contributed it
  • Fork the project
  • Start a feature/bugfix branch
  • Commit and push until you are happy with your contribution
  • Make sure to add tests for it. This is important so I don't break it in a future version unintentionally.
  • Please try not to mess with the Makefile and package.json. If you want to have your own version, or is otherwise necessary, that is fine, but please isolate to its own commit so I can cherry-pick around it.

LICENSE - "MIT License"

Copyright (c) 2013 Matteo Collina, http://matteocollina.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.

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