This is a keynote I gave at Oracle Code 2017 in New York: https://developer.oracle.com/code/newyork 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 we define the microservice architecture as an architectural style and explain what that actually means. You will learn why the architecture that you pick for your application matters. We describe how the primary goal of the microservice architecture is to enable continuous delivery/deployment and how it achieves that. You will learn how to solve key challenges with decomposing an application into microservices. We describe 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
https://www.manning.com/books/microservice-patterns

7. @crichardson
For more information
http://learnmicroservices.io

8. @crichardson
Agenda
A brief refresher on software architecture
From monolith to microservices
Microservices != silver bullet
Managing distributed data

9. 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

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

11. @crichardson
Architecture
=
Boxes and lines 😄

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

13. 4+1 view model
Logical
View
Process
View
Deployment
View
Implementation
View
Scenarios

14. 4+1 Logical view
Logical
View
Process
View
Deployment
View
Implementation
View
Scenarios
Elements: classes and packages
Relations: inheritance, associations, …

15. 4+1 Implementation view
Logical
View
Process
View
Deployment
View
Implementation
View
Scenarios
Elements: modules and components
Relations: dependencies

16. 4+1 Process view
Logical
View
Process
View
Deployment
View
Implementation
View
Scenarios
Elements: processes
Relations: IPC

17. 4+1 Deployment view
Logical
View
Process
View
Deployment
View
Implementation
View
Scenarios
Elements: “machines”
Relations: networking

18. 4+1 Scenarios
Logical
View
Process
View
Deployment
View
Implementation
View
Scenarios
Derived from use cases/stories
Animate the views

19. @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

20. @crichardson
Layered architectural style
Layer N
Layer N - 1
Layer N - 2
Well defined
responsibilities

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

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

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

24. @crichardson
Reducing lead time
Increasing deployment frequency

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

26. Agenda
A brief refresher on software architecture
From monolith to microservices
Microservices != silver bullet
Managing distributed data

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

36. @crichardson
A business has a business
capabilities
Acme, Inc
Order
Taking
Inventory
management
Delivery
management
A
Business Capability
is something a
business
does in order to
deliver value
…

37. @crichardson
Service = business capability
Order Taking
Service
Inventory
management Service
Delivery management
Service
…
Service

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
Example microservice architecture
Browser
Mobile
Device
Store
Front
Web App
API
Gateway
Catalog
Service
Review
Service
Order
Service
…
Service
Catalog
Database
Review
Database
Order
Database
…
Database
HTML
REST
REST
Supplier
Inbound
Gateway
Catalog update
messages
Supplier
System

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

43. @crichardson
Microservices enable
continuous delivery/deployment
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

44. @crichardson
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

45. @crichardson
Agenda
A brief refresher on software architecture
From monolith to microservices
Microservices != silver bullet
Managing distributed data

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

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

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

49. @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?

50. @crichardson
It depends!

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

52. @crichardson
The structure of a pattern
Resulting context
aka the situation
Name
Context
Problem
Related patterns
(conflicting) issues
etc to address
Forces
Solution

53. @crichardson
Example resulting context
Microservice
Architecture
Benefits
Drawbacks
Issues to resolve

54. @crichardsonMicroservice patterns
Communication patterns
Core
Cross-cutting concerns Security
Deployment
Maintaining data consistency
Database architecture
External API
Reliability
Discovery
Communication style
Testing
Observability
UI
Decomposition
API gateway
Client-side discovery
Server-side
discovery
Service registry
Self registration
3rd party registration
Multiple Services
per host
Single Service per
Host
Service-per-
Container
Service-per-VM
Messaging
Remote Procedure
Invocation
Database per
Service
Event-driven
architectureShared
database
Microservice
Chassis
Backend for front end
Event
sourcing
Transaction
log tailing
Database
triggers
Application
events
Monolithic
architecture
Microservice
architecture
CQRS
Motivating
Pattern
Solution
Pattern
Solution A Solution B
General Specific
Serverless
deployment
Circuit BreakerAccess Token
Domain-specific
Externalized
configuration
Service Integration
Contract Test
Service
Component Test
Exception
tracking
Distributed
tracing
Audit logging
Application
metrics
Log
aggregation
Health check
API
Service deployment
platform
Server-side page
fragment
composition
Client-side UI
composition
Decompose by
business capability
Decompose by
subdomain
Application patterns
Infrastructure patterns
Application Infrastructure patterns
Microservices pattern language: http://microservices.io

55. @crichardson
Agenda
A brief refresher on software architecture
From monolith to microservices
Microservices != silver bullet
Managing distributed data

56. @crichardson
Loose coupling =
encapsulated data
Order Service Customer Service
Order Database Customer Database
Order table
Customer
table
orderTotal creditLimit

57. @crichardson
How to enforce credit limit?
sum(order.total) <= customer.creditLimit

58. @crichardson
How to enforce credit limit?
BEGIN TRANSACTION
…
SELECT ORDER_TOTAL
FROM ORDERS WHERE CUSTOMER_ID = ?
…
SELECT CREDIT_LIMIT
FROM CUSTOMERS WHERE CUSTOMER_ID = ?
…
INSERT INTO ORDERS …
…
COMMIT TRANSACTION
Private to the
Order Service
Private to the
Customer Service
Distributed transactions

59. @crichardson
2PC is not an option

60. @crichardson
Saga
Instead: use event-driven sagas
Distributed transaction
Order Customer
Local transaction
Order
Local transaction
Customer
Local transaction
Order
Event
Event

61. @crichardson
Order Service
Saga-based, eventually consistent
order processing
Customer Service
Order created
Credit Reserved
Credit Check Failed
Create Order
OR Customer
creditLimit
creditReservations
...
Order
state
total
…
approve()/reject()
Event Handler
Event Handler
reserveCredit()

62. @crichardson
But how to reliably
update the database
and
publish events?

63. @crichardson
Event sourcing: event-centric
persistence
Event table
Entity type
Event
id
Entity
id
Event
data
Order 902101 …OrderApproved
Order 903101 …OrderShipped
Event
type
Order 901101 …OrderCreated

64. @crichardson
How to find recent, valuable
customers?
SELECT *
FROM CUSTOMER c, ORDER o
WHERE
c.id = o.ID
AND o.ORDER_TOTAL > 100000
AND o.STATE = 'SHIPPED'
AND c.CREATION_DATE > ?
Customer
Service
Order Service
What if event
sourcing is
used?…. is no longer easy

65. @crichardson
Command Query Responsibility
Segregation (CQRS)
Command side
Commands
Aggregate
Event Store
Events
Query side
Queries
(Materialized)
View
Events
POST
PUT
DELETE
GET

66. @crichardson
Queries database (type)
Command side
POST
PUT
DELETE
Aggregate
Event Store
Events
Query side
GET /customers/id
MongoDB
Query side
GET /orders?text=xyz
ElasticSearch
Query side
GET …
Neo4j

67. @crichardson
Summary
The goal of architecture is to satisfy non-functional
requirements
Use the appropriate architectural style
Small applications Monolithic architecture
Complex applications Microservice architecture
Use the pattern language to guide your decision making
Use an event-driven architecture for transactions and queries

68. @crichardson
@crichardson chris@chrisrichardson.net
http://learnmicroservices.io
Thank you!