A Pattern Language for Microservices

@crichardson

A pattern language for microservices

Chris Richardson

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

@crichardson chris@chrisrichardson.net http://learnmicroservices.io

Copyright © 2017. Chris Richardson Consulting, Inc. All rights reserved

@crichardson

Presentation goal

Overview of the microservice architecture pattern language

and how to use it to architect an

application

@crichardson

About Chris

@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

http://learnmicroservices.io

@crichardson

The paper that never made it to PLoP 2001

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Agenda

Why microservices?

Benefits of the microservice architecture

Microservices != silver bullet

The microservice pattern language

Applying the microservice pattern language

@crichardson

Modern software development: moving fast and not breaking things!

46x

440x

24x

5x lower

Amazon: ~0.001%

Netflix: 16 minutes

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How to move fast and not break things?

Architecture:

Process:

Small, autonomous teams ????

DevOps/Continuous delivery/deployment

Organization:

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The monolithic architecture

Tomcat

Browser

WAR

SQL database

HTML

REST/JSON

Client App

Simple to ….

Develop Test

Deploy Scale

Catalog Module

Reviews Module

Orders Module

StoreFront UI Module

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But successful applications keep

growing ….

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… and modularity breaks down…

http://www.laputan.org/mud/

“Shantytowns are squalid, sprawling slums.”

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Monolithic hell

Agile development and deployment

becomes impossible

By John Martin, Public Domain, https://commons.wikimedia.org/w/index.php?curid=3353638

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Monolithic hell:

Technology stack becomes increasingly obsolete BUT a rewrite is not feasible

The microservice architecture is an architectural style that

structures an application as a set of loosely coupled, services

organized around business capabilities

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The Microservice architecture tackles complexity through

modularization

Improved scalability is secondary

*

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Microservice architecture

Browser

Mobile Device

Content Router

API Gateway

Catalog Service

Review Service

Order Service

… Service

Catalog Database

Review Database

Order Database

… Database

HTTP /HTML

REST

REST

Browse & Search WebApp

Product Detail WebApp

….

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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

Organization:Small, agile, autonomous,

cross functional teams

Architecture: Microservice architecture

Enables

Enables Enables

SuccessfulSoftware

Development

Services =

testability and

deployability

Teams own services

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Smaller, simpler applications

Easier to understand, develop and test

Less jar/classpath hell - who needs OSGI?

Faster to build, test and deploy

Reduced startup time - improves MTTR

Scales development: develop, deploy and scale each service independently

Small, autonomous teams

Clearly defined responsibilities

Catalog Service

Review Service

Order Service

… Service

Catalog Team

Review Team

Order Team

… Team

Responsible for

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Easier to scale

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Improves fault isolation

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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

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Complexity

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

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Complexity of developing a distributed system

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Multiple databases &

Transaction managementMust use event-driven eventual consistency

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Complexity of testing a distributed system

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Complexity of deploying and operating a distributed system

You need a lot of automation: VM/container

orchestration or PaaS

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Developing and deploying features that span multiple services requires careful coordination

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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 make testing easier?

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

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

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Microservice pattern language =

collection of patterns that solve these

architecture, design, development and operational problems

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What’s a pattern?

Reusable solution to a problem

occurring in a particular context

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The structure of a pattern encourages objectivity

Resulting context

aka the situation

Name

Context

Problem

Related patterns

(conflicting) issues etc to address Forces

Solution Benefits

Drawbacks

Issues to resolve

Alternatives

Solutions to issues

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Microservice architecture pattern

Context Developing large, complex architecture

Problem What’s the runtime architecture?

Benefits Faster development Easy adopt new technologies

Drawbacks Complexity of a distributed system

Issues Decomposition Distributed system issues: IPC, discovery, …

Alternative patterns Monolithic architecture

Successor patterns Service Registry, API Gateway, …

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Microservices pattern language: http://microservices.io

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Microservices pattern language: layers

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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

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Predecessor - Successor ⇒

Sequence?

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Key patterns

Problem: What’s the architecture?Forces

Maintainability

Deployability

Testability

Extensibility

…

Monolithic architecture

Microservice architecture

Single deployable/executable OR

Tightly coupled services

Multiple loosely coupled services

Problem: How to decompose an application into services?

Forces

Stability

Cohesive

Loosely coupled

Not too large

Decompose bybusiness capability

Decompose bysubdomain

Organize around business capabilities

Organize around DDD subdomains

Problem: how to ensure services are loosely coupled?

Forces:

Services must be loosely coupled

Evolving schema of shared database = coordination

… Ensures loose coupling

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Problem: how to maintain data consistency?Context

• Each service has its own database

• Data is private to a service

Forces

Transactional data consistency must be maintained across multiple services

2PC is not an option

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Problem: how to perform queries?

CQRS

Context

Each service has its own database

Forces

Queries must join data from multiple services

Data is private to a serviceMaintain query views by subscribing to events

API Composition

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Problem: How do services communicate?

Messaging Remote ProcedureInvocation

Domain-specific

Forces

Services must communicate

Usually processes on different machines

…

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The rest are generic technical architecture patterns

= Undifferentiated heavy lifting!

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Problem: How to handle cross cutting concerns?

Microservice Chassis

Forces

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

Problem: How to deploy an application’s services?

Multiple Services per host

Single Service per Host

Service-per-Container

Service-per-VM

Serverless deployment

Service deployment platform

Forces

Multiple languages

Isolated

Constrained

Monitor-able

Reliable

Efficient

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Problem: How to discover a service instance’s network location?

Client-side discovery

Server-side discovery

Service registry

Self registration

3rd party registration

Forces

Client needs IP address of service instance

Dynamic IP addresses

Dynamically provisioned instances

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Problem: How do external clients communicate with the services?

API gateway

Backend for front end

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Problem: How to prevent a network or service failure from cascading?

Circuit Breaker

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Problem: how to monitor the behavior of your application?

Exception tracking

Distributed tracing

Audit logging Application metrics

Log aggregation

Health check API

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Summary

The monolithic architecture is a good choice for small/simple applications

Use the microservice architecture for large/complex applications

Microservice architecture != silver bullet

Use the microservice architecture pattern language to guide your decision making

@crichardson

@crichardson chris@chrisrichardson.net

http://learnmicroservices.io

Thank you!