This is a talk I gave at Code Freeze 2018: The microservice architecture is becoming increasingly popular. However, frequent references to using “a microservice to solve a problem” suggest that the concept is not universally well understood. In this talk, I define the microservice architecture as an architectural style and explain what that actually means. I also describe how the primary goal of the microservice architecture is to enable continuous delivery and deployment, and how it achieves that. You will learn why the architecture that you pick for your application matters. And you will learn how to solve key challenges with decomposing an application into microservices. This talk explains why there is no such thing as a microservice!

1. @crichardson
There is no such thing as a
microservice!
Chris Richardson
Founder of Eventuate.io
Founder of the original CloudFoundry.com
Author of POJOs in Action
@crichardson
chris@chrisrichardson.net
http://microservices.io
http://eventuate.io
http://plainoldobjects.com
Copyright © 2017. Chris Richardson Consulting, Inc. All rights reserved

2. @crichardson
Presentation goal
Define the Microservice Architecture
as an architectural style
Explain what that means and why it
matters

3. @crichardson
About Chris

4. @crichardson
About Chris
Consultant and trainer
focusing on modern
application architectures
including microservices
(http://www.chrisrichardson.net/)

5. @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)

6. @crichardson
About Chris
http://learnmicroservices.io
40% off
ctwcodefreeze18

7. @crichardson
Agenda
A brief refresher on software architecture
From monolith to microservices
Microservices != silver bullet
Applying the microservice pattern language

8. About software architecture
“The software architecture of a computing system is the
set of structures needed to reason about the system,
which comprise software elements, relations among
them, and properties of both.”
Documenting Software Architectures, Bass et al

9. @crichardson
Architecture
=
(elements, relations, properties)

10. @crichardson
Architecture
=
Boxes and lines 😄

11. @crichardson
Architecture is multi-dimensional
e.g. Structural, electrical, plumbing,
mechanical
Described by multiple views
View = (elements, relations, properties)

12. 4+1 view model
Logical
View
Process
View
Deployment
View
Implementation
View
Scenarios

13. 4+1 Logical view
Logical
View
Process
View
Deployment
View
Implementation
View
Scenarios
Elements: classes and packages
Relations: inheritance, associations, …

14. 4+1 Implementation view
Logical
View
Process
View
Deployment
View
Implementation
View
Scenarios
Elements: modules and components
Relations: dependencies

15. 4+1 Process view
Logical
View
Process
View
Deployment
View
Implementation
View
Scenarios
Elements: processes
Relations: IPC

16. 4+1 Deployment view
Logical
View
Process
View
Deployment
View
Implementation
View
Scenarios
Elements: “machines”
Relations: networking

17. 4+1 Scenarios
Logical
View
Process
View
Deployment
View
Implementation
View
Scenarios
Derived from use cases/stories
Animate the views

18. @crichardson
""… An architectural style determines
the vocabulary of components and
connectors that can be used in instances
of that style, together with a set of
constraints on how they can be
combined….. ””
David Garlan and Mary Shaw, An Introduction to Software
Architecture

19. @crichardson
Layered architectural style
Layer N
Layer N - 1
Layer N - 2
Well defined
responsibilities
Constrained
dependencies
Uses Uses
UsesUses

20. The role of architecture
Requirements
=
Functional requirements
+
Non-functional requirements (-ilities)
Domain
knowledge
Architecture

21. Important -ilities
Maintainability
Testability
Deployability
Evolvability
Scalability
Security
Reliability
…
https://en.wikipedia.org/wiki/Non-functional_requirement
Development
velocity
Sunday afternoon 😀

22. @crichardson
Businesses must innovate
faster
Build better software faster

23. @crichardson
Reducing lead time
Increasing deployment frequency

24. @crichardson
Modern software development: moving
fast and not breaking things!
46x
440x
24x
5x lower
Amazon: ~0.001%
Netflix: 16 minutes

25. @crichardson
Modern software development
Architecture:
Process:
Small, autonomous
teams
???
DevOps/Continuous delivery/deployment
Organization:

26. Agenda
A brief refresher on software architecture
From monolith to microservices
Microservices != silver bullet
Applying the microservice pattern language

27. @crichardson
Tomcat/App. Server
Traditional: Monolithic
architecture
Browser/
Client
WAR/EAR
MySQL
Database
Review
Management
Catalog
Management
Recommendation
Management
StoreFrontUI
Order
Management
HTML
REST/JSON
Logical view
Implementation view

28. @crichardson
The monolithic architecture
is an architectural style
that structures the application
as a single executable
component
Implementation view

29. -ilities of small monoliths
Maintainability
Testability
Deployability
…
https://en.wikipedia.org/wiki/Non-functional_requirement
😄

30. @crichardson
But successful applications
keep growing….
Development
Team
Application

31. @crichardson
… and growing
Development
Team A
ApplicationDevelopment
Team B
Development
Team C

32. @crichardson
Eventually:
agile
development
and deployment
becomes
impossible
=
monolithic hell

33. @crichardson
Technology stack becomes
increasingly obsolete
BUT
A rewrite is not feasible

34. -ilities of large monoliths
Maintainability
Testability
Deployability
…
https://en.wikipedia.org/wiki/Non-functional_requirement
😭

35. The microservice architecture
is an architectural style
that structures an
application as a
set of loosely coupled,
services organized around
business capabilities

36. @crichardson
Application
Service = business capability
Acme, Inc
Order
Taking
Inventory
management
Delivery
management
Business Capability = something a business does to deliver value
…
Order
Service
Inventory
Management
Service
Delivery
Management
Service …
Service

37. @crichardson
Service = independently
deployable component
Command
Query
API
Event
Publisher
Event
Subscriber
API
Client
Consumer facing Implementation
Synchronous:
REST, gRPC, …
Asynchronous:
Command/Reply, Notification
Service database
Events
Events
Synchronous:
REST, gRPC, …
Asynchronous:
Command/Reply, Notification
Data owned by the service
Data replicated from elsewhere
SLA

38. Service size is secondary
microservice architecture

39. Service:
Meaningful business functionality
Developed by a small team
Minimal lead time/high deployment
frequency

40. Microservices
=
Microservice architecture
=
Application architecture
No such thing as a microservice

41. @crichardson
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
….
Supplier
Inbound
Gateway
Catalog update
messages
Supplier
System

42. -ilities of a microservice
architecture
Maintainability
Testability
Deployability
…
https://en.wikipedia.org/wiki/Non-functional_requirement
😄

43. @crichardson
Microservices
DevOps/Continuous delivery/deployment
of large/complex applications

44. @crichardson
Process:
Continuous delivery/deployment
Organization:
Small, agile, autonomous,
cross functional teams
Architecture:
Microservice architecture
Enables
Enables
Enables
Successful
Software
Development
Services improve
testability
and
deployability
Teams own services

45. @crichardson
Microservices evolve the
technology stack
Pick a new technology when
Writing a new service
Making major changes to an existing service
Let’s you experiment and fail safely

46. @crichardson
Agenda
A brief refresher on software architecture
From monolith to microservices
Microservices != silver bullet
Applying the microservice pattern language

47. @crichardson
No silver bullets
http://en.wikipedia.org/wiki/Fred_Brooks

48. @crichardson
Drawbacks of microservices
Complexity
Development: IPC, partial failure, distributed data
Testing: Integration, end to end, …
Deployment
…

49. @crichardson
Are microservices a good fit
for my application?

50. @crichardson
Do I have the pre-requisites in place:
automated testing
automated provisioning
…..
?

51. @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?

52. @crichardson
It depends!

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

54. @crichardson
What’s a pattern?
Reusable solution
to a problem
occurring
in a particular context

55. @crichardson
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

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

57. @crichardson
Agenda
A brief refresher on software architecture
From monolith to microservices
Microservices != silver bullet
Applying the microservice pattern language

58. @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

59. @crichardson
Key patterns

60. Issue: What’s the deployment
architecture?
Forces
Maintainability
Deployability
Testability
…
Monolithic
architecture
Microservice
architecture
Single deployable/
executable OR
Tightly coupled services
Multiple loosely coupled
services

61. Issue: How to decompose an
application into services?
Forces
Stability
Cohesive
Loosely coupled
Not too large
Decompose by
business capability
Decompose by
subdomain
Organize around
business capabilities
Organize around DDD
subdomains

62. @crichardson
Issue: 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

63. @crichardson
Issue: 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 service
Maintain query views by
subscribing to events
API
Composition

64. @crichardson
The rest are generic technical
architecture patterns
=
Undifferentiated heavy lifting!

65. @crichardson
Issue: How do services
communicate?
Messaging
Remote Procedure
Invocation
Domain-specific
Forces
Services must
communicate
Usually processes on
different machines
…

66. @crichardson
Issue: How to handle cross
cutting concerns?
Microservice
Chassis
Forces
Every service must
implement logging;
externalize configuration;
health check endpoint;
metrics; …

67. Issue: 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

68. @crichardson
Issue: 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

69. @crichardson
Issue: how to monitor the
behavior of your application?
Exception
tracking
Distributed
tracing
Audit logging
Application
metrics
Log
aggregation
Health check
API

70. @crichardson
Summary
The goal of architecture is to satisfy non-functional
requirements
For continuous delivery/deployment use the appropriate
architectural style
Small applications Monolithic architecture
Complex applications Microservice architecture
Use the pattern language to guide your decision making

71. @crichardson
@crichardson chris@chrisrichardson.net
http://learnmicroservices.io
Thank you!
40% off
ctwcodefreeze18