A Pattern Language for Microservices Chris Richardson

A pattern language for microservices Chris Richardson

Founder of Eventuate.io Founder of the original CloudFoundry.com Author of POJOs in Action

@crichardson [email protected] http://microservices.io http://eventuate.io http://plainoldobjects.com

Overview of the microservice architecture pattern language and how to use it to architect an application

@crichardson About Chris

Consultant and trainer focusing on modern application architectures including microservices (http://www.chrisrichardson.net/)

@crichardson About Chris

Founder of a startup that is creating an open-source/SaaS platform that simpliﬁes the development of transactional microservices (http://eventuate.io)

@crichardson About Chris

https://www.manning.com/books/microservice-patterns @crichardson Agenda

Why microservices? Beneﬁts of the microservice architecture Microservices != silver bullet The microservice pattern language Applying the microservice pattern language

@crichardson Let’s imagine you are building an online store

REST/JSON Browser/ StoreFrontUI Client HTML

Catalog Module

Recommendation SQL Module Database

Review Module

Order Module Layered and modular

@crichardson Problem: what’s the deployment architecture?

@crichardson Forces

Businesses must innovate faster ⇒ Develop more complex, higher-quality software faster

@crichardson Traditional Monolithic architecture

WAR/EAR

StoreFrontUI

HTML Catalog REST/JSON Browser/ Module MySQL Client Database Recommendation Module

Review Module

Order Module

Tomcat

@crichardson Simple to ….

Develop Test Deploy Scale

@crichardson Successful applications have a habit of growing ⇒ Big, complex, monolithic applications

@crichardson Eventually, agile development and deployment becomes impossible

@crichardson Requires long-term commitment to a technology stack

@crichardson Monolithic hell

Development is slow Application is becoming a big ball of mud No one fully understands the application It’s written in an obsolete technology stack

@crichardson The microservice architecture

Loosely coupled services organized around business capabilities

@crichardson The Microservice architecture tackles complexity through modularization

@crichardson Microservice architecture

HTML Store Catalog Catalog Browser Front UI Service Database

REST Review Review Service Database API Gateway REST Order Order Service Database

Mobile Device … … Service Database @crichardson Agenda

Why microservices? Beneﬁts of the microservice architecture Microservices != silver bullet The microservice pattern language Applying the microservice pattern language

@crichardson Microservices enable continuous delivery/deployment

Process: Continuous delivery/deployment

Enables Enables Successful Software Development

Organization: Architecture: Small, agile, autonomous, Microservice architecture cross functional teams Enables

@crichardson Smaller, simpler applications

Easier to understand and develop Less jar/classpath hell - who needs OSGI? Faster to build and deploy Reduced startup time

@crichardson Scales development: develop, deploy and scale each service independently

Catalog Responsible Catalog Team for Service

Small, autonomous teams Review Review Clearly deﬁned Team Service responsibilities Order Order Team Service

… … Team Service Easier to scale

@crichardson Improves fault isolation

@crichardson Easily evolve your technology stack

... and fail safely @crichardson Agenda

Why microservices? Beneﬁts of the microservice architecture Microservices != silver bullet The microservice pattern language Applying the microservice pattern language

@crichardson No silver bullets

http://en.wikipedia.org/wiki/Fred_Brooks @crichardson Complexity

http://highscalability.com/blog/2014/4/8/microservices-not-a-free-lunch.html

@crichardson Complexity of developing a distributed system

@crichardson Multiple databases & Transaction management

Must use event-driven eventual consistency

@crichardson Complexity of testing a distributed system

@crichardson Complexity of deploying and operating a distributed system

Yo u n e e d a lot o f automation: VM/container orchestration or PaaS

@crichardson Developing and deploying features that span multiple services requires careful coordination

@crichardson Agenda

Why microservices? Beneﬁts of the microservice architecture Microservices != silver bullet The microservice pattern language Applying the microservice pattern language

@crichardson Are microservices a good ﬁt for my application?

@crichardson When using microservices:

How to decompose an application into services? How to deploy an application’s services? How to handle cross cutting concerns? Which communication mechanisms to use?

How do external clients communicate with the services? How does a client discover the network location of a service instance? How to prevent a network or service failure from cascading to other services?

How to maintain data consistency and implement queries?

How to understand the behavior of an application and troubleshoot problems?

How to make testing easier?

How to implement a UI screen or page that displays data from multiple services?

@crichardson Microservice pattern language = collection of patterns that solve these architecture, design, development and operational problems

@crichardson What’s a pattern?

Reusable solution to a problem occurring in a particular context

@crichardson The structure of a pattern

Name

Context aka the situation

Problem (conﬂicting) issues Forces etc to address Solution Resulting context Related patterns @crichardson Beneﬁts

Resulting context Drawbacks

Issues to resolve

@crichardson Alternative pattern: Different solution to same problem

Related patterns

Successor pattern: Solves problem introduced by this pattern

@crichardson Microservices pattern language: http://microservices.io

Motivating Solution Pattern Pattern Application patterns

Solution A Solution B Server-side page General Speciﬁc CQRS Service Integration fragment Event Contract Test sourcing composition Decompose by Event-driven business capability Shared Database per architecture database Service Transaction Client-side UI log tailing Service composition Component Test Decompose by Database architecture subdomain Testing UI Database Decomposition triggers Application Application Audit logging events metrics Monolithic Maintaining data consistency architecture

Application Infrastructure patterns Distributed Health check tracing API Remote Procedure Messaging Invocation Microservice Externalized Access Token Circuit Breaker Chassis conﬁguration

Exception Log Domain-speciﬁc Reliability tracking aggregation Cross-cutting concerns Security Communication style Observability

Microservice architecture Core Client-side discovery Self registration

Infrastructure patterns

Multiple Services Single Service per Service registry per host Host API gateway

Serverless deployment Server-side 3rd party registration discovery Backend for front end Discovery Service-per- Service-per-VM Container

Service deployment External API platform Deployment Communication patterns

Microservice patterns @crichardson Microservices pattern language: http://microservices.io

Motivating Solution Pattern Pattern Application patterns

Application Infrastructure patterns Distributed Health check tracing API Remote Procedure Messaging Invocation Microservice Externalized Access Token Circuit Breaker Chassis conﬁguration

Exception Log Domain-speciﬁc Reliability tracking aggregation Cross-cutting concerns Security Communication style Observability

Microservice architecture Core Client-side discovery Self registration

Infrastructure patterns Decomposition Multiple Services Single Service per Service registry per host Host API gateway

Base Serverless deployment Server-side 3rd party registration Technical discovery Backend for front end Discovery Architecture Service-per- Service-per-VM Container

Service deployment External API platform Dev/Ops Deployment Concerns Communication patterns Microservice patterns @crichardson Agenda

Why microservices? Beneﬁts of the microservice architecture Microservices != silver bullet The microservice pattern language Applying the microservice pattern language

@crichardson The pattern language guides you when developing an architecture

What architectural decisions you must make For each decision: Available options Trade-offs of each option

@crichardson Issue: What’s the deployment architecture?

Monolithic Forces architecture Single deployable/ executable OR Maintainability Tightly coupled services Deployability Testability Extensibility Multiple loosely coupled … Microservice architecture services Issue: How to decompose an application into services?

Forces Organize around business capabilities Decompose by Stability business capability Cohesive Decompose by Loosely coupled subdomain Organize around DDD Not too large subdomains Issue: How to deploy an application’s services?

Forces Multiple Services Single Service per Multiple languages per host Host

Isolated Serverless deployment Constrained

Service-per- Service-per-VM Monitor-able Container Reliable Service deployment Efﬁcient platform Issue: How do services communicate?

Forces

Remote Procedure Messaging Services must Invocation communicate

Usually processes on Domain-speciﬁc different machines …

@crichardson Issue: How to discover a service instance’s network location?

Forces Client-side discovery Self registration Client needs IP address of service instance

Dynamic IP addresses Service registry Dynamically provisioned

instances Server-side 3rd party registration discovery

@crichardson Issue: How to handle cross cutting concerns?

Forces

Every service must Microservice implement logging; Chassis externalize conﬁguration; health check endpoint; metrics; …

@crichardson Issue: how to maintain data consistency?

Context

• Each service has its own database Event sourcing Event-driven architecture • Data is private to a service Transaction log tailing Forces

Database Transactional data consistency triggers must be maintained across Application events multiple services

2PC is not an option

@crichardson Issue: how to perform queries?

Context Each service has its own database CQRS Forces Queries must join data from multiple services Data is private to a service Maintain query views by subscribing to events

@crichardson Issue: how to monitor the behavior of your application?

Application Audit logging metrics

Distributed Health check tracing API

Exception Log tracking aggregation

@crichardson Summary

The monolithic architecture is a good choice for small/simple applications Use the microservice architecture for large/complex applications Micro service architecture != silver bullet Use the microservice architecture pattern language to guide your decision making

@crichardson @crichardson [email protected]

Thank you! http://learnmicroservices.io @crichardson