isabella232 / underverse

Underverse is a small backlog/queue manager that detects when items in your backlog are out of sync

Underverse

Underverse is a small backlog/queue manager that detects when items in your backlog are out of sync and issues a fetch event to retrieve the missing items. This module makes the following assumptions about your backlog of data:

• The backlog works with a bag of a ids.
• The ids a nummeric which equals the position of the backlog.
• The ids are ordered.
• The backlog has limit.
• The backlog resets it's ids once the limit is reached.

Build status

Installation

The installation is done through npm

npm install underverse --save

Add the --save if you want to save the module in your package.json.

Usage

The module is initialized with the size of the backlog;

var Underverse = require('underverse')
  , uv = new Underverse(1000);

The snippet above creates a new underverse that works with a backlog that can contain 1000 items. You should set the initial id of log. For example if your queue is filled with 100/10000 slots:

uv.cursor(100);

As it could be possible that your messages get out of sync if you use a remote backlog (for example a reconnect) you can listen to the fetch event to know which ids are missing.

uv.on('fetch', function (missing, mark) {

})

The fetch event receives 2 arguments, an array of missing id and a mark function. The mark function allows you set all ids in to a fetching state so you won't retrieve duplicate fetch calls that retrieve the same information. If you call the mark function with a boolean true it will mark all missing ids as received.

When you have received a message from your backlog call the uv.received() method with the id.

uv.received(10)

and that's it. Take a look at the tests for some examples.

License

MIT