WHY

1. Managing dependencies in Node.js
   • Encourages Single Responsibility Principle
   • Discourages God Objects
   • Facilitates Test Doubles
2. Lean and unopnionated
   • Not a framework
   • Wires components through their manifest
   • Everything can be a component

The Systemic redemption

• Common microservices structure
• No concern about start / stop order
• Graceful shutdown out-of-the-box

---

• Steep learnign curve
• Not widely used

Main concepts

• SYSTEMS
• COMPONENTS
• START interface
• Starts the component
• Exposes component's methods
• STOP interface
• Stops the component
• Closes any dangling connection
• DEPENDENCY INJECTION
• MANIFESTS
• RUNNERS

talk is cheap

Systems and Runners

system

const components = path.join(__dirname, 'components')
const exampleSystem = () => new System({ name: 'exampleSystem' }).bootstrap(components);
					

runner

runner(exampleSystem(), { logger: emergencyLogger }).start((err, components) => {
  	if (err) {
		emergencyLogger.error(err, message);
		process.exit(1);
  	}
  	logger.info('The system has started');
});
					

Manifests and Components

manifest

const loggerSystem = () => new System({ name: 'loggerSystem' })
	.add('logger', logger())
	.dependsOn('config')
					

component

const logger = () => {
	const start = async ({config}) => {
		console.log(`starting logger with config: ${config}`);
		return console
	};
	const stop = async () => {
		console.log('stopping logger');
	};

	return { start, stop };
};
					

wrap up

Systemic and microservices

• Hexagonal architecture
• Single responsibility
• Fine-grained separation of concerns
• Versioning and aliasing
• Tests stubs
• Out-of-the-box systemic components

Generator-Systemic

“ A generator for a systemic microservice ”

• yo systemic
• yo systemic --showcase

• open source on github
• available on npm

yo systemic

A white canvas service into which creating the components you do prefer according to your specific business logic.

Out-of-the-box non-business-logic-related components

yo systemic

yo systemic --showcase

A not so white canvas with a given business logic already in place to help you better understand how to get the best out of Systemic.

yo systemic --showcase

yo systemic --showcase