pub/sub upon update of key/value pair

[ORESoftware]

my goal is to use Redis pub/sub (hopefully using this library) to send messages upon an update or insert of a Redis key.

Does this library go low-level enough for that? How can I invoke an nrp.emit upon a Redis key/value update?

Is the best way to do this using keyspace notifications?

http://redis.io/topics/notifications

Please let me know, thanks

[RangerMauve]

Currently, this library only handles pub/sub and nothing more. Though it shouldn't be too hard to build a wrapper over it that does what you want.

You can access the raw Redis connection object with nrp.emitter. You could then potentially wrap over the get/set/etc functions in the emitter in order to have them do a nrp.emit call on whatever key is being modified.

This would need to be a separate library as it is outside the scope of this one.

[ORESoftware]

thanks, sounds like this library could easily do this. if you do add this functionality, it would be great to have a quick example, something along the lines of:

nrp.on('DEL key:74iegeag2', function (data) {
console.log('Hello ' + data.name);
});

I guess the emitting part would be taken care of by Redis itself, but a simple example of a handler with the right syntax would be good. Does this make sense?

[RangerMauve]

Again, that functionality is something that'd be best left to a library that build on top of this one.
The docs on the Redis API can be found here

A starting point might look like:

function make_wrapper(config){
  var nrp = new NRP(config);
  return {
     nrp: nrp,
     get: function(key, cb){
        return nrp.emitter.get(key, cb);
     },
     set: function(key, value, cb){
       nrp.emitter.set(key, value, function(err, result){
         if(err) return cb(err, result);
         nrp.emit("SET "+key, value);
         cb(err, result);
       })
     }
  }
}

[ORESoftware]

with all due respect, don't you think it's better to not wrap wrappers? It seems it would be best for me to fork this repo and fix the internals than to wrap a wrapper, no?

[ORESoftware]

this repo should ideally be doing the lower level listening to DELs, SETs, etc. Wrapping this library in order to do that is just going to create confusion, IMO

[RangerMauve]

When people think "redis pub sub", I doubt they expect much more than pub/sub functionality. And wrapping a wrapper is totally fine since that's how you use modules to create new modules.

If you want I can create this wrapper for you, but it would be more maintainable to keep functionality separated.

[ORESoftware]

It would be super awesome if you could create that, I am personally looking to listen to events such as these

http://redis.io/topics/notifications

DEL generates a del event for every deleted key.
SET and all its variants (SETEX, SETNX,GETSET) generate set events. However SETEX will also generate an expire events.
...
etc

please LMK what you think, thanks

[RangerMauve]

Created redis-update-events, please open an issue there with the minimal number of events you were thinking of.

[ORESoftware]

cool, thanks RM...can you reconcile this redis-update-events library with this answer here http://stackoverflow.com/questions/29785346/redis-client-to-listen-to-set-and-del-events/29785902#29785902

do you really think they should be separate libs?

[RangerMauve]

Yeah, since this would be events specific to operations rather than general pub/sub. I actually think I might not even use node-redis-pubsub for the other library since if you're only listening on events published by Redis itself, then you don't need to have a publish socket.

[ORESoftware]

huh