This is a talk that I gave at a T Systems DevOps day. It's answers to Frequently Asked Questions about the Microservice Architecture

1. @crichardson
Microservices - an architecture
that enables DevOps
Chris Richardson
Microservice architecture consultant and trainer
Founder of Eventuate.io
Founder of the original CloudFoundry.com
Author of POJOs in Action and Microservices Patterns
@crichardson
chris@chrisrichardson.net
http://adopt.microservices.io
Copyright © 2020. Chris Richardson Consulting, Inc. All rights reserved

2. @crichardson
What you will learn
Answers to Frequently Asked
Questions about the
Microservice Architecture

3. @crichardson
About Chris
http://adopt.microservices.io

4. @crichardson
Discounts
35% discount
mtpsystems20
$120 discount coupon
KLDPZOJE
http://adopt.microservices.io

5. @crichardson
Agenda
1. What is the microservice architecture?
2. How small is a microservice?
3. Why is the microservice architecture important?
4. Is the monolithic architecture an anti-pattern?
5. What are the key challenges with using microservices?
6. How do you migrate a monolith to a microservice
architecture?

6. Pattern: microservice
architecture
Highly maintainable and
testable
Minimal lead time (time from
commit to deploy)
Loosely coupled
Independently deployable
Implements a business
capability
Owned/developed/tested/
deployed by a small team
An architectural
style
that structures an
application as a
set of deployable/
executable units,
a.k.a. services
A service is:

7. @crichardson
Food to Go: Microservice
architecture
Browser
Mobile
Application
API
Gateway
Order
Service
Restaurant
Service
Delivery
Service
…
Service
Order
Database
Restaurant
Database
Delivery
Database
…
Database
REST
REST
JavaScript
Message
Broker

8. @crichardson
Service architecture “mirrors”
the business
FTGO business
Kitchen Service
Delivery Service
Order Taking
Kitchen
Delivery
Accounting
….
….
Service
Order Service
Accounting Service
Maps to
Maps to
Maps to
Maps to
Maps to
Area of the business,
a.k.a.
Subdomain or Business Capability

9. @crichardson
API
The structure of a service
Operations
Event
Publisher
Commands
Queries
Synchronous
REST/gRPC
Asynchronous
Messaging
Events
Event
Subscriber
API
Client
Invokes
Operations
Events
Service
Database
Private!

10. @crichardson
Agenda
1. What is the microservice architecture?
2. How small is a microservice?
3. Why is the microservice architecture important?
4. Is the monolithic architecture an anti-pattern?
5. What are the key challenges with using microservices?
6. How do you migrate a monolith to a microservice
architecture?

11. @crichardson
Microservices should be
team-sized
Service
https://microservices.io/patterns/decomposition/service-per-team.html
Owned by a
team
Owns one
service
Not to exceed
cognitive capacity of
team

12. @crichardson
Service too large*: split service
Service
Small, autonomous
team
Service
Service
*Too large => unable to achieve desired -ilities, e.g.
short lead time (build/test/deploy time)

13. @crichardson
Agenda
1. What is the microservice architecture?
2. How small is a microservice?
3. Why is the microservice architecture important?
4. Is the monolithic architecture an anti-pattern?
5. What are the key challenges with using microservices?
6. How do you migrate a monolith to a microservice
architecture?

14. @crichardson
https://www.ft.com/content/f9356bdc-3102-11ea-a329-0bcf87a328f2
https://www.ft.com/content/3f498e64-1aa6-11ea-97df-cc63de1d73f4
https://techcrunch.com/2019/06/18/the-rise-of-the-gig-economy-helps-london-based-insurtech-zego-to-raise-42m/
C
O
VID
-19
The marketplace/world is
Volatile, Uncertain,Complex,
Ambiguous
Businesses must be nimble,
agile, and innovate faster
IT must deliver software
rapidly, frequently and reliably

15. @crichardson
Key development metrics
Faster
More reliable

16. @crichardson
Success triangle
Process: Lean + DevOps/Continuous Delivery & Deployment
Organization:
Small, loosely coupled,
teams
Architecture:
????
Deliver software
rapidly, frequently,
reliably and
sustainably
Enables
Enables

17. Required architectural quality
attributes (a.k.a. -ilities)
“Complete their work without
communicating and coordinating with
people outside their team”
“Make large-scale changes to the design
of their system without depending on
other teams to make changes in their
systems or creating significant work for
other teams”
“We can do most of our testing without
requiring an integrated environment.”
“We can and do deploy or release our
application independently of other
applications/services it depends on.”
Loosely coupled
(Conway’s law)
Modular
Testable
Deployable
API encapsulates design decisions

18. @crichardson
Architecture quality attributes
for sustainable development
Time
Technology A Technology B
V1 V2 V3 V…
Importance
The importance of a technology changes over time
Evolvability - Must be able to upgrade the
technology stack of long-lived applications

19. @crichardson
Process: Lean + DevOps/Continuous Delivery & Deployment
Architecture:
microservices
Testability
Deployability
Loose coupling
Deliver changes to
long-lived
applications rapidly,
frequently and reliably
Organization: Small, long-
lived, product-centric,
autonomous teams

20. @crichardson
Microservices experiment safely
and evolve the technology stack
Java
Java
Java
Java
Java
Golang
“GoLang
is cool!”
Java
Java
Java
“Kotlin
is better!”
Java
Kotlin

21. @crichardson
Agenda
1. What is the microservice architecture?
2. How small is a microservice?
3. Why is the microservice architecture important?
4. Is the monolithic architecture an anti-pattern?
5. What are the key challenges with using microservices?
6. How do you migrate a monolith to a microservice
architecture?

22. @crichardson
Tomcat/App. Server
Food To Go: Monolithic
architecture
Browser/
Client
WAR/EAR
MySQL
Database
Delivery
management
Order
Management
Kitchen
Management
Web UI
Restaurant
Management
HTML
REST/JSON
The application

23. -ilities of small monoliths
Testability
Deployability
Maintainability
Modularity
Evolvability
✅
✅
✅
✅
✅
(full rewrite)

24. @crichardson
Rapid, frequent and reliable delivery
eventually becomes impossible
Time
Maintainability
Testability
Deployability
Modularity
Evolvability
Size/
Complexity
-ilities required to be competitive
Risk of
disruption

25. @crichardson
Lack of sustainability:
Many decisions are global = difficult/
impossible to change incrementally
Programming language
Versions of dependencies - libraries and
frameworks
…

26. @crichardson
Agenda
1. What is the microservice architecture?
2. How small is a microservice?
3. Why is the microservice architecture important?
4. Is the monolithic architecture an anti-pattern?
5. What are the key challenges with using microservices?
6. How do you migrate a monolith to a microservice
architecture?

27. @crichardson
Challenge: complexity of
building a distributed system
Development:
IPC, partial failure
Distributed data - sagas etc
Testing: Integration, end to end, …
Deployment
…

28. @crichardson
Challenge: minimizing
coupling between services
Minimize design-time coupling
Design-time coupling = services changing in lockdown
Reduces productivity by increasing coordination between teams
How: DRY services, Iceberg services, avoiding shared database/
business logic libraries
Minimize runtime coupling
Runtime coupling - e.g. chains of REST calls
Reduces availability
How: use Self-contained services

29. @crichardson
Agenda
1. What is the microservice architecture?
2. How small is a microservice?
3. Why is the microservice architecture important?
4. Is the monolithic architecture an anti-pattern?
5. What are the key challenges with using microservices?
6. How do you migrate a monolith to a microservice
architecture?

30. @crichardson
Strangler
Application
http://www.martinfowler.com/bliki/StranglerApplication.html
Incrementally migrate
functionality
from
existing application
to
new (strangler)
application

31. @crichardson
Strangling the monolith
Monolith
Time
Monolith
Service
Monolith
Service
Service
Monolith
Service
Service
Service
Service
…. Monolith
Service
Service
Service
Service
Service
Service
Service
Service
Service
Service
Service
Service
Service
Service
Service
Service
….
Strangler application
The strangler application grows larger over time
The monolith shrinks over time
Service
Service
Service
Service
Service
Service
Service
Service
New
features

32. @crichardsonDatabase
Module
Iteratively: Module => Service
Monolith Service
API Gateway
Request
Module
Request
Monolith
Database
Module
Database
Module
Integration
glue
API
API

33. @crichardson
Start with the modules that
give you the greatest return
on investment (ROI)

34. Cost vs. Benefit of extraction
Benefit
Solves a significant
problem
Velocity frequently
updated
Scalability Conflicting
resource requirements
…
Cost
Cost of changing the
monolith and adapting/
rewriting module
Difficulty in decoupling/
breaking dependencies
Need to participate in
sagas/compensating
transactions

35. @crichardson
Iteratively: New feature = Service
Monolith Service
API Gateway
Request
DatabaseDatabase
Integration
glue

36. @crichardson
Measuring success
Success != Number of Microservices
Improved metrics:
Reduced lead time
Increased deployment frequency
Reduced changed failure rate
Improvements in other -ilities
…
Anti-pattern:
Microservices as the goal
https://chrisrichardson.net/post/antipatterns/2019/01/14/antipattern-microservices-are-the-goal.html

37. @crichardson
Summary
Modern enterprises need to deliver software rapidly frequently, reliably and
sustainably
This requires a loosely coupled, modular, testable and deployable
architecture
The monolithic architecture is not anti-pattern but its often best for smaller
applications
The microservice architecture is often better for large/complex
applications
Loosely coupled services are essential
Use the Strangler pattern to migrate a monolith to microservices

38. @crichardson
@crichardson chris@chrisrichardson.net
http://adopt.microservices.io
Questions?
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