redis-scheduler

redis-scheduler

Use redis keyspace notifications to trigger timed events inspired by http://blog.codezuki.com/blog/2013/07/07/redis-queue.

Features

• Listen for expiring events by registering handlers to simple redis keys.
• Multiple handlers can be set per key.
• Events can be rescheduled or cancelled with automatic handler cleanup.
• Can listen for patterns with one or many handlers using regular expressions.

Requirements

• Redis 2.8.0 or higher.
• Enabling keyspace notification by either setting notify-keyspace-events Ex in redis configuration file.

Installation

$ npm install redis-scheduler

Usage

Initialization

Create a new scheduler instance

var Scheduler = require('redis-scheduler');
var scheduler = new Scheduler({ host: 'localhost', port: 6379 });

#new Scheduler(options)

• options - Can be object or null. If null defaults to host: 'localhost', port: 6579 and db: 0
  • host (string) - Redis connection host.
  • port (number) - Redis connection port.
  • db (number) - Redis zero-based numeric database index
  • path (string) - Redis pid file
  • password (string) - Redis password
  • redisOptions (object) - Redis options

Scheduling event

Add a timed event.

var expirationTime = 1000;

function eventTriggered(err, key) {
  console.log(key + ' triggered');
}

scheduler.schedule({ key: 'test-key', expire: expirationTime, handler: eventTriggered }, function (err) {
  // Schedule set
});

#schedule(options, cb)

• options
  • key (string) - The key of event to store.
  • expire (date/number) - Date/number of milliseconds until expiration.
  • handler (function) - Function to call when scheduled time occurs.
• cb - Function to call after schedule set.

Adding event handler

You can add multiple handlers per event.

scheduler.addHandler({ key: 'test-key', handler: function () {
  console.log('another event');
}});

#addHandler(options, fn)

• options
  • key (string) - The event key to add the handler for (can be simple string or regex string in case of patterns).
  • handler (function) - The extra handler to add when the event is triggered.
  • pattern (boolean) - Designates whether key is a regular expression.

###Rescheduling an Event###

Reschedules a scheduled event. Will take either a new date to trigger or explicit milliseconds.

scheduler.reschedule({ key: 'test-key', expire: 3000 }, function () {
  console.log('rescheduled');
});

#reschedule(options, cb)

• options
  • key (string) - Event to reschedule.
  • expire (number) - Milliseconds/date to reset expiration to.
• cb (function) - Function to call after rescheduling is complete.

###Cancel scheduled item###

Cancels a scheduled event and cleans up handlers

scheduler.cancel({ key: 'test-key' }, function () {
  console.log('canceled');
});

#cancel(options)

• options
  • key (string) - Key to remove event for. If a regular expression will cancel all pattern matching handlers.

###A event pattern matching ###Close scheduler###

Disconnects and closes all connections to redis and cleans up all existing event handlers

#end()

Testing

Clone the repo and run from the project root:

$ npm install
$ npm test

Examples

$ cd examples/events
$ npm install
$ node simple.js
$ node multi-handlers.js
$ node loop.js
$ node reschedule.js