Microservices metrowest web developers 2016-09-14

Microservices
What are they, why use them, and how?

Who Am I?
Rob Raisch
Senior Staff Software Engineer @ Yieldbot
Team Lead - Config Services
More than 30 years online experience - "Internet Greybeard"

Overview
What are Microservices?
Definition, History
Why are they desirable?
Characteristics, Drawbacks
How should I organize/define them?
Business Domains
How about a quick example?

What are Microservices? - Definition
An Architectural Design Pattern of:
Small, Autonomous Modular Services
That Are Independently and Automatically Deployable
Using Lightweight Communication Mechanisms

What are Microservices? - Definition
An Architectural Design Pattern of:
Small, Autonomous Modular Services
That Are Independently and Automatically Deployable
Using Lightweight Communication Mechanisms
Do Only One Thing And Do It Well

What are Microservices? - Example
Monolithic Service
Graphic blatently stolen from microservices.io

What are Microservices? - Example
Microservices
Graphic blatently stolen from microservices.io

Microservices - History
A World of Small Interconnected Things
Unix Pipefitting - $> cat file.txt | awk '{print $2}' | sort | uniq > result.txt
Remote Procedure Call (RPC) - ASN.1, CORBA/IDL, etc.
Message Passing and Event Busses - Document Object Model, PubSub, ZeroMQ, etc.
SOA - XML, WSDL, SOAP, etc.
Microservices

Microservices - History
A World of Small Interconnected Things
Unix Pipefitting - $> cat file.txt | awk '{print $2}' | sort | uniq > result.txt
Remote Procedure Call (RPC) - ASN.1, CORBA/IDL, etc.
Message Passing and Event Busses - Document Object Model, PubSub, ZeroMQ, etc.
SOA - XML, WSDL, SOAP, etc.
Everything is deeply intertwingled. - Ted Nelson

Why Are Microservices Desirable?

Increase Cohesion
Reduce Coupling
Improved Resilience
Optimized for Replaceability
Better Alignment With Business Processes
Better Composability
Better Scaling
Technological Heterogeneity

Increase Cohesion
Group related functionality together
"Gather together those things that change for the same reason and separate
those things that change for different reasons."
- Robert C. Martin's Single Responsibility Principle

Reduce Coupling - Separation of responsibilities
Coupling - the manner and degree of interdependence between software
components.
Connascence - where a change to one software component requires changes
to other components.

Improved Resilience
Monolithic systems tend to fail completely.
Design so a failure of one software component will not cause the entire system
to fail, thus improving overall "fault tolerance"
Service boundaries become natural "bulkheads" and so reduce the "cascade"
of failure.

Optimized for Replaceability
As long as service contracts remain the same, all components can be easily
replaced.
Lessen technical debt
Reduce costs to replace underlying technologies

Better Alignment With Business Processes
Organized around business domains
Reduce development team size
Help focus participation from elsewhere in the organization

Better Composability
Monolithic systems cannot be easily reorganized as needs change
Lots of little independent workers that can be organized in different ways
Better software reuse - "DRY it up!"

Better Scaling
In Monolithic systems, everything must be scaled together
Using routing, requests can be directed to one of several instances of the
same service (see nginx)
The architecture can be scaled as needed

Technological Heterogeneity
Monolithic systems are typically written in a single language.
No requirement that all services be expressed in the same language
Use "the right tool for the right job"

Ease of Deployment
New functionality can be easily deployed as needed.
No "BIG" deploys reduce downtime.
"Deliver often" - Continuous Integration/Deployment

What Are The Drawbacks Of Microservices?
Distributed systems can be much more complex than monolithic ones.
The "Big Picture" can be difficult to envision without good documentation.
Operational Overhead
Interactions can be hard to track without copious, centralized logging.
Network latency must be monitored and managed well.

How Should Microservices Be
Designed?

How Should Microservices Be Designed?
Identify Domains Aligned to Business Units
Authorization
Payments - Deposits, Ledgers, Reconciliation
Billing
Reporting
Support
Not Components! Responsibilities!

Identify Stakeholders And Include Them In Design Process
Carve Out Well-Defined Functionality
Keep Martin's Single Responsibility Principle in mind at all times.

Identify Stakeholders And Include Them In Design Process
Keep Martin's Single Responsibility Principle in mind at all times.
"Gather together those things that change for the same reason and separate those
things that change for different reasons."

The BIG QUESTION:
How to determine the best size for a microservice?

The BIG QUESTION:
The BIG ANSWER:
As Small As They Need To Be To Solve A Need

The BIG QUESTION:
The BIG ANSWER:
As Small As They Need To Be To Solve A Need
BUT NO SMALLER!

An Example Using Node/Seneca

Microservice in Seneca - Server
const _ = require('lodash');
const SenecaFactory = require('seneca');
const seneca = SenecaFactory();
seneca.add('cmd:sum', (msg, respond) => {
let errs = [];
const left = Number(_.get(msg,'left',0));
const right = Number(_.get(msg,'right',0));
if(_.isNaN(left)) errs.push(new Error('left operand must evaluate to a number'));
if(_.isNaN(right)) errs.push(new Error('right operand must evaluate to a number'));
if(errs.length) {
respond(errs);
}
else {
const result = Math.floor(left) + Math.floor(right);
respond(null, { answer: result });
}
});

Microservice in Seneca - Server Side Call
// To call microservice from the same process…
seneca.act({cmd: 'sum', left: 1, right: 2}, (err, result) => {
if (err) {
console.error(err);
return;
}
console.log(`The result is ${result}`);
});

Summary
Architectural Pattern of Small, Independent Loosely-Coupled Services
Many Useful Benefits For Medium/Large Systems
Though By No Means A Panacea!
Do Only One Thing But Do It Very Well
Organize Around Business Domains
As Small As Needs Dictate But No Smaller

We Are Hiring!
IT Lead
Engineering Manager, Infrastructure
Front End Software Engineer
Server-side Javascript Engineer
DevOps Engineer
Software Test Engineer - Ad Serving Platform
Platform Software Engineer - Ad Serving

Thanks for your time!
rraisch@yieldbot.com

Microservices metrowest web developers 2016-09-14

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