storage-backed-queue

AngularJS service that persists and retries a queue of promise-based asynchronous function calls to HTML5 storage.

This can be useful when you need to ensure calls to $http are succesful, along with their then success callback, even after a browser restart, or after failed requests due to a dropped internet connection.

Because failures are automatically retried, recoverable failures of $http, such as from insufficient permissions due to a session expiring, should be handled using http interceptors. You should ensure that any requests are idempotent on the server, as the browser treating a request as failed might have been succesful from the server's point of view.

Installation

The easiest way to install is be using Bower, which downloads all the requied dependencies

bower install intelligentgolf/storage-backed-queue --save

Usage

Add the dependency to your AngularJS app:

// Add module dependency 
angular.module('myApp', ['storage-backed-queue']);

Then use it by injecting StorageBackedQueue into your services:

angular.service('MyService', function(StorageBackedQueue) {
  // Use StorageBackedQueue
});

To allow queues to be reconstructed after a browser restart, functions must be registered with a unique identifier.

var sbQueue = StorageBackedQueue('requests');

sbQueue.register('http', function(params) {
  return $http(params).then(function(results) {
	// Process results;
  });
});

Then to add a function call to the queue, unique identifier must be passed to run, along with the parameters to pass to the registered function.

sbQueue.run('http', {
	'method': 'POST',
	'url': '/someUrl',
	'data': {'key': 'value'}
});

After a browser restart, once a function has been (re)-registered, then its queue will be processed, recovering any past queued parameters from HTML5 storage.

Limitations

Parameters passed to the queue are stored in HTML5 storage, and so must be JSON encodable, and completely reconstructable from JSON encode -> JSON decode path. This means they cannot hold circular references, or references to functions.