This a simple wrapper for pubsub via redis.
var redisPubSub = require('redis-pubsub-emitter');
// The factory method takes the same parameters as redis.createClient()
var redisPubSubClient = redisPubSub.createClient(6379, 'localhost');
// Both on() and once() support *-wildcards, therefore the actual topic
// is always passed through
function handleNews(payload, topic) {
console.log('News on channel %s: %s', topic, payload);
};
redisPubSubClient.on('news.uk.*', handleNews);
// removeListener() will also remove the subscription from redis if
// no other handler is attached
redisPubSubClient.removeListener('news.uk.*', handleNews);
// Publish send a message to redis. This will also call all event
// listeners that are attached to that topic
redisPubSubClient.publish('news.uk.politics', 'message');
// Emit will ONLY emit to local event listeners, no redis message
// will be send
redisPubSubClient.emit('news.uk.*', 'fake news', 'news.uk.fake');Behaves pretty much like events.EventEmitter with the difference
that ````emit()calls the internal event handlers without publishing to a topic whilstpublish()``` is the function that actually sends
a message to redis.
All the usual functions from EventEmitter work like you'd expect,
e.g. on(), once(), setMaxListeners(), removeListener() and
removeAllListeners(). See http://nodejs.org/api/events.html
Wildcards * are allowed for on() and once() are allowd as
described in http://redis.io/topics/pubsub
Listeners will receive two parameters, a payload as javascript object and the actual channel name (useful in case wildcards have been used).
Multiple subscriptions to the same topic will not create multiple subscriptions with redis, it's therefore safe to subscribe to the same topic(-pattern) more than once. If all listeners are removed from one topic the subscription will be removed from redis.