Voka

Reliabe pub-sub broker, using Redis and Nodejs

TL;DR

Create a subscriber

var voka = require("voka");
voka.subscriber(function(e, sub) {
  if(e) {
    return console.error(e);
  }
  sub.subscribe("channel1", function(data) {
    console.log(data);
  });
});

Create a publisher

var voka = require("voka");
voka.publisher(function(e, pub) {
  if(e) {
    return console.error(e);
  }
  setInterval(function() {
    pub.publish("channel1", Date.now());
  });
});

Create a hub that can send and recieve message

voka.hub(function(e, hub) {
  //publish
  hub.publish("foo", "bar");
  //subscribe
  hub.subscribe("foo", function(message) {
    //messages won't be sent to the hub itself
    //so no `bar` will get here
  });
});

Redis

Tell voka how to connect to a Redis server:

voka.publisher({
  redis: {
    //redis host
    host: "localhost",
    //redis port
    port: 6379,
    //redis authpass
    authpass: "helloworld"
  }
}, function(e, pub) {
  //TODO
});

Reliability

Slow joiner

Delay to publish

voka.publisher({ delay: 5000 }, function() {
  //delay 5 seconds to run this callback
  //TODO
});

Wait for subscribers

voka.publisher({ least: 4 }, function(e, pub) {
  //wait for at least 4 subscribers before running this callback
  
  //There are some related events:
  pub.on("least:match", function(numberOfLivingSubscribers) {
    //the least amount of subscribers are connected
  });
  
  pub.on("least:unmatch", function(numberOfLivingSubscribers) {
    //one or more subscribers are disconnected and the number of subscribers doesn't match
  });
  
  
  pub.on("reject", function(channel, data) {
    //messages are rejected if the number of subscribers doesn't match
  });
  
});

Heartbeat

Subscribers are required to send heartbeat to broadcast their existences.

A publisher can report the changes:

pub.on("report", function(data) {

  data.livingList; //names of the connected subscribers
  data.dropList; //names of disconnected subscribers since the last heartbeat

});

Producer & consumer

• multiple subscirbers can be assigned with an identical name for load balance
• multiple publishers can be assigned with an identical name for more horsepower

Notes

1. hiredis doesn't compile in node v0.11.x, so pure javascript implementation is used if you are running v0.11.x
2. For back-compatibilities, traditional promise-based style is used

License

MIT