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.
The installation is done through npm
npm install underverse --save
Add the --save if you want to save the module in your package.json.
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.
MIT