10 Reasons to use OSGi for your next cloud app

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Ten reasons to use OSGi for your next cloud app @pbakker

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Paul Bakker @pbakker

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Reason nr Developer Productivity 1

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Code Maven build full project Deploy to app server Re-initialize full app Typical Java development workﬂow…

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Typical OSGi development workﬂow… “Like working with a scripting language”

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How does it work? Class loader per bundle OSGi supports updating a bundle On compile, bundle is rebuild and re-installed

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Reason nr No more ClassNotFoundException 2

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Imports / Exports OSGi bundles deﬁne explicitly what classes they import Imports must be exported by some bundle Imports are calculated from your byte code

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Example code z

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Import packages are generated Import-‐Package: org.apache.felix.dm;version=“[4.0,5)", org.osgi.framework;version="[1.3,2)"

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The framework tells you what’s missing Unable to resolve 1.0: missing requirement [1.0] osgi.wiring.package; (&(osgi.wiring.package=org.apache.felix.dm) (version>=4.0.0)(!(version>=5.0.0))) Forgot to install Dependency Manager bundle…

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API versioning Deploy multiple versions of an API Import a speciﬁc version range Semantic Versioning

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Reason nr Great for Cloud Deployment 3

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Great for (Cloud) deployment No application server Executable JAR ﬁle Very small memory footprint Perfect for building Docker containers

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Building a binary gradle build export java -‐jar MyApp.jar

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Dockerﬁle FROM jeanblanchard/busybox-‐java:8 COPY release/myapp.jar /app/myapp.jar WORKDIR /app EXPOSE 8080 CMD java -‐jar myapp.jar

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Great commercial support RTI Kubernetes based clusters Logging and Monitoring for OSGi Automated Blue/Green deployments

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Reason nr Maintainable architecture 4

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Maintainable architecture Implementation hiding Enforce module boundaries Modules during development, build and runtime

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Bundles and services Only APIs are exported, the bundle’s contract Services provide functionality True decoupling Service Registry Bundle registering a service Bundle using a service Publish MyInterface Lookup MyInterface

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Data Business UI Big ball of mud Big ball of mud Big ball of mud

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Data Business UI

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Rooms Resource AngularJS Client Rooms Service RabbitMQ Service STOMP AMQP RabbitMQ Chat Log Mongose Jongo REST Personalized Ad Generator Word Counter Product Service MySQL

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Rooms Resource AngularJS Client Rooms Service RabbitMQ Service STOMP AMQP RabbitMQ Chat Log Mongo Jongo REST Personalized Ad Generator Word Counter Product Service MySQL Each part is a separate OSGi bundle

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Reason nr Dependency Injection 5 @ServiceDependency

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Reason nr The road to Micro Services 6

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Best preparation for Micro Services OSGi services are micro services within a VM Easy to migrate to remote services when needed Perfect balance between “Monolith First” and Micro Services from te get go

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OSGi Remote Services OSGi spec for remote service discovery and invocation Pluggable discovery and transport No code changes required!

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Client Server

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Reason nr All the libraries you need 7

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REST Scheduling Mongo JPA Web Resources Blob Stores Remote Services Security Email Config Components No core framework or half a zillion dependencies!

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Amdatu REST example

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Amdatu Mongo example Amdatu Mongo Service Setup Object Mapper Execute query

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Reason nr Plugin systems 8 Plugin Registry Plugin Plugin Plugin

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core.jar myplugin.jar Install plugin by installing a bundle

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Real world examples Amdatu Bootstrap (even directly from Git repos) Spring Roo Eclipse Glassﬁsh …