1) Lean microservices can be implemented on OSGi by creating independently deployable services that communicate through OSGi services. This allows for flexible packaging and deployment compared to frameworks like Spring Boot. (2) OSGi supports semantic versioning, remote services, and flexible packaging of modular bundles. (3) A demo chat application shows how different components like an IRC connector, display, and shell integration can be implemented as bundles that communicate through OSGi services locally or remotely.

1. Lean microservices
on OSGi
By Christian Schneider
Open Source Architect at Talend
chris@die-schneider.net
@schneider_chris

2. Participate in Demo
Connect to irc network freenode
Channel #osgichat

3. Microservices
...way of designing software applications as suites of independently deployable services.... organization around business
capability, automated deployment, intelligence in the endpoints, and decentralized control of languages and data. - Martin
Fowler
● Create application out of independently deployable services
● Verticals around business capabilities
● Decentralized data
● Automated deployment
● 1 service per process
● Lightweight communications between services (typically REST)

4. Spring boot
● Framework for micro service development based on spring
● Easy to start. Paste snippets of “starter” dependencies into pom
● Convention over configuration
● Good docker and cloud support

5. The Dark side of
microservices

6. No, no, no. Quicker, easier,
more seductive...
Are microservices
stronger than OSGi?

7. Dependencies between microservices

8. Operations
Container vessel - Application Server

9. Microservices operation - Theory

10. Microservices operation - Practice

11. Microservices can not cure bad design

12. Microservices with
spring-boot…
What is wrong with it?
● Lots of dependencies already
at design time
● Microservices always must
communicate remotely
● Proprietary Annotations / API
● No flexibility in packaging
1 Microservice = 1 Deployment
Unit = 1 Process

13. A small spring boot project
● Pollutes the classpath
● Difficult to establish rules which APIs to use
90
dependencies
20 MB
jar file

14. Why is OSGi
different?
● Coding against APIs and specs
● Self describing modules
(bundles)
● OSGi services to communicate
between bundles
● Semantic versioning
● Remote Service Admin for
Remote calls and REST
● Flexible packaging

15. Semantic Versioning
● MAJOR version - incompatible API changes,
● MINOR version - added functionality in a backwards-compatible manner
● BUGFIX version - backwards-compatible bug fixes
Mind the difference between API and SPI.

16. Remote Service Admin
● Exports and imports OSGi services
● Service Properties to mark for export and configure transports, …
● Highly customizable (Policies, Transports, Serialization, Discovery)

17. Rest services with RSA
● Just JAX-RS annotations on interface
REST Endpoint User bundle
HTTP
OSGi
service
CXF Transport for
Aries RSA
Creates
Topology
Manager
Detects
Selects
transport

18. Lets see it in practice
Small chat application
● Modules talk to each other using
an OSGi ChatListener interface
described in API bundle
● IRC connector using camel
● Shell integration using gogo
● Tinkerforge Display and Motion
detector
● Optional Remoting using Aries
RSA

19. Chat API
Chat shell integration
Tinkerforge LCD display
IRC Connector
IRC
All in one
● 1 Process
● 6MB runnable jar
● No remote calls inside application
● Still modular as bundles only coupled
through API and OSGi service

20. Container vessel - OSGi deployment in one process

21. Chat API
IRC Connector
Aries RSA
IRC
Microservice Deployment
Chat API
Tinkerforge LCD and
motion detect
Aries RSA
Chat API
Chat shell integration
Aries RSA
Zookeeper

22. Microservice Deployment
● Same bundles as before
● As many deployment units as needed
● Each deployment unit can scale
● Runnable jars or docker containers
● Cloud native if needed
● Aries RSA overhead 300 KB + 800 KB zookeeper lib
● Remote calls or local calls as needed
● Many options for remotings (tcp, fastbin, SOAP, REST, JMS)

23. But beware of the same management issues as any
other micro services

24. Demo time

25. OSGi can scale from very small to very
large
But no simple cure for the operational problems of microservices

26. Unsure if you actually need a
microservice architecture?
● Develop your application using modular bundles
● Stay on single process as long as possible
● Decide about the packaging and deployment as late as
possible
● Deploy only as fine granular as needed

27. Further Reading
● Achim Nierbeck - Microservices on OSGi
● Milen Dyankow - Microservices and
Modularity
● OSGi Chat example code
● Example for REST export using Aries RSA
and CXF