npm:transaction-group

README

transaction-group

Collect [optionally unique] objects over a period of time and then act on them

example

In this example we collect item upates from a hypothetical pubsub module. Once the interval has elapsed, the function passed to TXG will be excuted with the items added during the time period.

var sub = require('pubsub');
var TXG = require('transaction-group');

var txg = TXG(function (items) {
    //process updates for items.
    items.forEach(function (item) {
        /* ... */
    });
}, { interval : 5000 }); //process transaction groups every 5 seconds

sub.subscribe('/item/updates', function (item) {
    txg.add(item, item.item_id);
});

api

var txg = TXG(callback, opts);

callback(items[, done]) - [function] the function which will be called to process the transaction group
- items - [array] the array of items that are part of this txg
- done - [function] - optional function to call when you are done procesing a txg. If this is specified in your callback signature then callback will not be called again until after you call done.
opts - [object] options object
- interval - [integer] the duration of time, in milliseconds to collect objects
- timeout - [integer] the duration of time, in milliseconds to wait for your callback to finish
  - requires a done function in your callback
  - value for timeout must be greater than 0
  - if done() is not called by timeout milliseconds then that transaction group will be emitted on the timeout event and txg will process the next transaction group

txg.add(item[, index])

item - [anything] the object to store for the next transaction group
index - some value that identifies the uniqueness of the object you are collecting. This can be used to make sure that there is only one instance of an object waiting to be processed. If the item already exists in the current transaction group, then the most recent item will over- write the existing one.

events

txg.on('timeout', function (items) {});

Called when timeout has elapsed if opts.timeout is specified and your callback function has a done() function

license

MIT

Usage no npm install needed!