The Promise of Node.js
Building Scalable Web Applications
Hi!
Product Lead @ Pulse Energy
Paul Teehan
Energy Analytics Developer @ Pulse Energy
Big Data
+
Web technology
+
Data analytics
+
Behavioural science
Energy utilities
Smart grid data
Make the world a better place
Platform for building scalable web applications
Javascript virtual machine
Core set of libraries
Server-side Javascript - WTF?
A brief history of Javascript (abridged)
1995: Invented by Brendan Eich
XMLHttpRequest
2004: Ajax becomes de facto
2006: Javascript gets respect
2008: Chrome launched - browser wars resume
2009: Node.js launched
2014
- Javascript: programming language of the web
- V8: one of the most heavily optimized, widely used VMs
- Node.js: unprecedent growth, web-centric community
2014
Server-side Javascript - who cares?
Node.js: asynchronous, evented I/O
Event-driven architecture (SEDA)
Low CPU, high I/O
Thread-based architectures: scale later
Service-oriented architecture
Node.js: built from the ground up for asynchrony
Node.js event loop
Dealing with asynchrony
Callbacks
Callback example
fs.readFile(filename, [options], callback)var callback = function (err, data) {}
Callback example
fs.readFile('/buildings.csv', function (err, data) {
if (err) {
throw err;
}
console.log(data);
});
Callback results
var result = fs.readFile('/buildings.csv', function (err, data) {
if (err) {
throw err;
}
return data;
});
console.log(result); // ????
Callback chaining
var loadBuildings = function (buildingType, cb) {
fs.readFile('/buildings.csv', function (err, data) {
if (err) {
cb(err);
}
processData(data, cb);
});
}
Callback hell
What's the alternative?
Promises
JQuery Promises
Promise example
loadBuildings(buildingType).then(function (buildingData) {
return processData(buildingData);
}).fail(function (err) {
return handleError(err);
});
EventEmitters
process.on('uncaughtException', function (err) {
logger.error(err, 'Unhandled error');
process.exit(1);
});
process.on('exit', function () {
logger.info('Process is exiting');
});
More information