This document discusses the evolution from monolithic applications to service-oriented architectures (SOA) and microservices. It begins by describing the monolith approach of one giant application that does everything. It then explains that SOA breaks applications into services that communicate with each other. Microservices take this further by making each service independent and focused on doing one thing well. The document outlines some key differences between SOA and microservices, such as microservices having no shared schema/contract and being independently deployable. Overall, it provides an overview of moving from monolithic applications to microservices.

1. Road to
Microservices
Think small to go big
@parallelit

2. Monolith SOA Microservices
Road to Microservices

3. Monolith SOA Microservices
Road to Microservices

4. Monolith SOA Microservices
Road to Microservices

5. One giant app that did everything

6. Three-tier architecture

7. Monolithic application
• Web assets (CSS, JS, Images, etc.)
• REST API
• Data Persistance tier
• Sessions
• Authentication
• Security
• …

8. The age of the monolith is over

11. What is SOA?
• Service-Oriented Architecture (SOA) is an architectural
style that supports service-orientation. Service-
orientation is a way of thinking in terms of services
• A service is a function that is well-defined, self-
contained, and does not depend on the context or state
of other services
• A service-oriented architecture is essentially a collection
of services. These services communicate with each other
• There are two roles in SOA: a service provider and a
service consumer

12. SOA in plain english
Consumer Applications House
Bridge Services Infrastructure
Provider Components City

13. The four tenets of SOA
• Boundaries are explicit
• Services are autonomous
• Services share schema and contract, not class
• Service compatibility is based on policy
Don Box, Microsoft

14. Boundaries are explicit
• A boundary represents the border between a
service’s public interface and its internal,
private implementation
• A service's boundary is published by means of
WSDL and may include assertions dictating the
expectations of a given service

15. Services are autonomous
• Services are entities that are independently
deployed, versioned, and managed

16. Services share schema and
contract, not class
• A service's contract is generally defined using WSDL
or BPEL for aggregations of services. Service's
contract defines the behavior of the service itself
• Schema defines the structure and content of the
messages
• Classes combine behavior and data (messages) into a
single programming-language or platform-specific
construct. Services communicating using XML
schema-based messages are agnostic to both
programming languages and platforms, ensuring
broader levels of interoperability

17. Service compatibility is based
on policy
• It is not possible to communicate some requirements for
service interaction in WSDL alone
• Policy expressions can be used to separate structural
compatibility (what is communicated) from semantic
compatibility (how or to whom a message is communicated)
• Policy expressions provide a configurable set of interoperable
semantics governing the behavior and expectations of a given
service
e.g. A government security service may require a policy
enforcing a specific service level (Passport photos meeting
established criteria must be cross-checked against a terrorist
identification system)

18. What are microservices?
“The microservice architectural style is
an approach to developing a single
application as a suite of small services,
each running in its own process and
communicating with lightweight
mechanisms, often an HTTP resource
API”
Martin Fowler, ThoughtWorks

19. What are microservices?
Every microservice does one thing and
one thing well

20. What are microservices?
“Fine grained SOA”
Adrian Cockcroft, Netflix

21. SOA vs Microservices (1)
SOA four tenets:
• Boundaries are explicit
• Services are autonomous
• Services share schema and contract, not class
Microservices does’t expose schema and contract. Each
services communicate with lightweight mechanisms
(often an HTTP resource API)
• Service compatibility is based on policy

22. SOA vs Microservices (2)
Microservices must be independently
deployable by fully automated
deployment machinery, whereas SOA
services are often implemented in
deployment monoliths
Torsten Winterberg, Oracle ACE Director

23. Codebaseissmall

24. How small is small?
“Something that could be rewritten in
two weeks”
Jon Eaves, Real Estate Australia

25. Autonomous
• PaaS or own OS process
• Communication via network calls
• Black-box
• Application Programming Interface (API)

26. Technology heterogeneity

27. Embrace new technology

28. Resilience

29. Scaling

30. Ease of deployment

31. Composability

32. Optimizing for replaceability

33. Organization alignment

34. Disadvantages
• Network issues
• Distributed computing
• Authentication (SSO, Stateless, Mutual, etc.)
• Service discovery

35. Microservice Federation