Channels

Channels keeps your messages in order for different endpoints(channels) of your nodeJS application.

In Etherpad Channels is used to ensure changes for specific pads have their own channel (gateway) and changesets (planes) are assigned to specific channels (gateways).

Channels is useful if you need to have lots of different IO operations on different endpoints that you need to keep in order.

Example

/*
  Imagine we have an airport with 2 gateways. Every gateway can only be used by one plane at the same time. 
  The planes should land in the order they registered their landing at the airport
*/

var channels = require("channels");

function doLanding(landing, callback)
{
  setTimeout(function()
  {
    console.log(new Date().toString() + " " +landing.planeName + " landed on " + landing.gateway);
    callback();
  },1000);
}

var airport = new channels.channels(doLanding);

airport.emit("gateway1", {planeName: "superjet1", gateway: "gateway1"});
airport.emit("gateway2", {planeName: "superjet2", gateway: "gateway2"});

airport.emit("gateway1", {planeName: "superjet3", gateway: "gateway1"});
airport.emit("gateway2", {planeName: "superjet4", gateway: "gateway2"});

airport.emit("gateway1", {planeName: "superjet5", gateway: "gateway1"});
airport.emit("gateway2", {planeName: "superjet6", gateway: "gateway2"});

Output

Thu Jul 28 2011 18:44:52 GMT+0100 (BST) superjet1 landed on gateway1
Thu Jul 28 2011 18:44:52 GMT+0100 (BST) superjet2 landed on gateway2
Thu Jul 28 2011 18:44:53 GMT+0100 (BST) superjet3 landed on gateway1
Thu Jul 28 2011 18:44:53 GMT+0100 (BST) superjet4 landed on gateway2
Thu Jul 28 2011 18:44:54 GMT+0100 (BST) superjet5 landed on gateway1
Thu Jul 28 2011 18:44:54 GMT+0100 (BST) superjet6 landed on gateway2