sloppy-queue-flow

A constructor function for queue-flow that sacrifices queue correctness for parallelism

npm install sloppy-queue-flow
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Quick install instructions

For Node.js

npm install sloppy-queue-flow

Note: sloppy-queue-flow version 0.1.10 requires Node version 0.8.17 and NPM version 1.2.0 to take advantage of the new peerDependencies mechanism. This means that if you require a specific version of queue-flow in your application, sloppy-queue-flow will use that version rather than pulling in its own copy. It is otherwise identical to version 0.1.9.

For developers, npm test to check your changes (using nodeunit) haven't broken existing functionality. Literate programming documentation can be found inside of the /docs directory, generated by docco.

Usage

For details on how it all works in general, see the queue-flow library for detailed API documentation and usage examples.

sloppy-queue-flow is a replacement constructor function that eliminates guarantees on queue order to allow execution on each item in the queue to traverse through the flow as fast as possible. This is a trade-off that makes sense for things like the Express-like server example from the main queue-flow library, but would break the dependency resolution example. Essentially, sloppy-queue-flow is only valid for cases where all operations are commutative, which is not everything, but does cover a surprising number of cases.

To use sloppy-queue-flow in Node.js, simply:

var q = require('queue-flow');
var sloppy = require('sloppy-queue-flow');

q('sloppyQueue', sloppy) // Code here

When should you use sloppy-queue-flow over the "regular" queue-flow?

Are the items in the queue totally independent?

Such as HTTP request-response pairs that will be served to totally different users and have no impact on one another? Then sloppy-queue-flow will improve the performance of the system and push the bottlenecks out to your I/O.

Can the items in the queue be processed in any order even if the outcome depends on all of them?

Such as 4*3*2 == 2*3*4? Then sloppy-queue-flow can be used, but you must be cautious. If at any time in the future you change it to something that can't be reordered, such as 4/3/2 != 2/3/4, then you need to drop usage of sloppy-queue-flow.

General Rule of Thumb

queue-flow as a source code organizer for event/request handlers can use sloppy-queue-flow.

queue-flow as a data processor should not use sloppy-queue-flow, unless you're sure it won't screw things up and you're sure the queueing is the bottleneck (if each step along the flow has a predictable processing time, sloppy-queue-flow will not provide any measureable advantage if the number of stages exceeds the number of processor cores).

License (MIT)

Copyright (C) 2012-2013 by David Ellis

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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