How to receive Redis expire events with node?

Question

I want to listen the expire events from Redis. I've configured on my redis.conf the notify-keyspace-events "AKE" and this is my code on node:

const redis = require('redis');
const client = redis.createClient();
const subscriber = redis.createClient();
const KEY_EXPIRING_TIME = 10; // seconds

client.setex('myKey', KEY_EXPIRING_TIME, 'myValue');

subscriber.on('message', function(channel, msg) {
  console.log( `On ${channel} received ${msg} event`);
});

subscriber.subscribe('myKey', function (err) {
  console.log('subscribed!');
});

What I hope is to see in 10 seconds that the event is triggered. The setex command works correctly, in 10 seconds the key is not in the database, I have the problem when I try to capture the event.

What am I doing wrong?

Answer 1

It is in fact possible to listen to the "expired" type keyevent notification using a subscribed client to the specific channel ('__keyevent@db__:expired') and listening to its message event.

no need for setInterval / setTimeout or additional libraries

Proof-of-concept (working : tested with NodeJS v.9.4.0)

const redis = require('redis')
const CONF = {db:3}
var pub, sub
//.: Activate "notify-keyspace-events" for expired type events
pub = redis.createClient(CONF)
pub.send_command('config', ['set','notify-keyspace-events','Ex'], SubscribeExpired)
//.: Subscribe to the "notify-keyspace-events" channel used for expired type events
function SubscribeExpired(e,r){
 sub = redis.createClient(CONF)
 const expired_subKey = '__keyevent@'+CONF.db+'__:expired'
 sub.subscribe(expired_subKey,function(){
  console.log(' [i] Subscribed to "'+expired_subKey+'" event channel : '+r)
  sub.on('message',function (chan,msg){console.log('[expired]',msg)})
  TestKey()
 })
}
//.: For example (create a key & set to expire in 10 seconds)
function TestKey(){
 pub.set('testing','redis notify-keyspace-events : expired')
 pub.expire('testing',10)
}