OSGi – introduction to

application modularity

Marek Koniew

the most probable future of core+

What is OSGi

OSGi Alliance - Open Services Gateway Initiative

http://www.osgi.org

Membership $5000 - $25000 per year.

Latest specification version is 5 (no implementation yet).

Implementations:

60

OSGi overview

Bundles - OSGi components made by the developers.

Services - connects bundles in a dynamic way.

Modules - defines how a bundle can import and export code.

Life-Cycle - to install, start, stop, update, and uninstall bundles.

58

Modularity Benefits

What OSGi brings:

Reuse – 3rd party components available as OSGi bundles

Dynamic updates – bundle can be updated in runtime

Adaptive – design forces to work when not everything is available

Versioning – many component versions at the same time

Simple – core API less than 30 classes/interfaces

Small – OSGi v4 implementation is 300KB JAR

Fast – working inside singe JVM – no serialization needed.

Lazy – loading only what is necessary

Reduced complexity – modules hides complexity from outside

56

OSGi bundles

Jar files

Exporting packages : bundle definition

Exporting services : runtime

54

OSGi bundles – manifest.mf

Bundle-Activator: com.hybris.kernel.regioncache.osgi.OSGiBundleActivator

Bundle-Name: kernel-cache

Bundle-Version: 1.0.1

Export-Package: com.hybris.kernel.regioncache

Import-Package: com.hybris.commons.tenant,com.hybris.kernel.api; version="[3.0,4)"

Private-Package: com.hybris.kernel.regioncache.counters,com.hybris.kerne

l.regioncache.impl,com.hybris.kernel.regioncache.jmx,com.hybris.kernel.

regioncache.osgi,com.hybris.kernel.regioncache.region

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OSGi bundles - versions

Transitive dependencies conflict is not a problem anymore:

50

OSGi bundles - lifecycle

48

GoGo shell

OSGi bundles - activator

public class OSGiBundleActivator implements org.osgi.framework.BundleActivator

{

@Override

public void start(final BundleContext context) throws Exception

{

System.out.println("Activating osgi module " +

context.getBundle().getSymbolicName());

}

@Override

public void stop(final BundleContext context) throws Exception

{

System.out.println("Stop " + context.getBundle().getSymbolicName());

}

}

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Whiteboard pattern

Also applicable to configuration bundle.

How it behavies when there is no service at the moment?

Configuration can be provided this way.

44

Semantic versioninig - definition

1.0.0.abc

Major.Minor.Micro.Qualifier

• Major: incompatible change for providers and consumers

• Minor: incompatible change for providers

• Micro: compatible change

• Qualifier: anything (e.g. Build identity)

42

Semantic versioninig - reference

OSGI

http://www.osgi.org/wiki/uploads/Links/SemanticVersioning.pdf

SemVer.org

http://semver.org/

Eclipse

http://wiki.eclipse.org/Version_Numbering

40

Semantic versioninig – version ranges

38

Semantic versioninig – bundle hell

Bundle hell

Feature grouping

Apache ACE

36

OSGi tools (selection)

Bndtools

Import analysis

Semantic versioning

Integrated testing

Apache Felix

OSGi implementation

Maven integration

GoGo shell

Apache ACE

Manage and distribute components

34

Bndtools

Eclipse only

Feature reach

Import analysis

Repositories

OBR resolving (OSGi bundle repository)

Semantic versioning

Instant builder

Integrated testing

Live presentation

Releasing and version control

Calculated imports

Integration tests

29

OSGi testing

Unit tests – use mocks

Integration tests

bndtools in eclipse

bndtools ant task (also from maven)

tycho-surefire maven plugin

OSGi Assertion library

https://github.com/dpishchukhin/org.knowhowlab.osgi.testing

assertServiceAvailable(CacheController.class)

findBundle(„kernel-cache”).stop()

…

27

Maven integration

<packaging>bundle</packaging>

…

<plugin>

<groupId>org.apache.felix</groupId>

<artifactId>maven-bundle-plugin</artifactId>

<configuration>

<instructions>

<Export-Package>com.hybris.kernel.regioncache</Export-Package>

<Private-Package>com.hybris.kernel.regioncache.*</Private-Package>

<Bundle-Activator>

com.hybris.kernel.regioncache.osgi.OSGiBundleActivator

</Bundle-Activator>

<Import-Package>com.hybris.kernel.api</Import-Package>

</instructions>

</configuration>

</plugin>

25

OSGi – DI

Declarative services

http://wiki.osgi.org/wiki/Declarative_Services

Blueprint

http://wiki.osgi.org/wiki/Blueprint

CDI-OSGi (draft)

https://speakerdeck.com/paulbakker/rfc-193-osgi-cdi

• Hide OSGi service management complexity

• Still to implement manually situation when service is not available !!!

• Only singleton services supported. RFC-195 (draft) introduces prototype.

23

OSGi – Declarative Services

Functionality provided by OSGi 4 specification

package com.hybris;

import aQute.bnd.annotation.component.*;

@Component

Class Hello {

private Log log;

@Reference(unbind = „unSetLog”)

public void setLog(Log log) { … }

public void unSetLog(Log log) { … }

}

Manifest.mf

Service-Component: com.hybris.*;

21

OSGi – Blueprint

Defined in OSGi v4.2

Implemented

Apache Aries

Eclipse Gemini

Spring DM (dead)

Manifest.mf

Spring-Context: config/hello-context.xml; wait-for-dependencies:=true; timeout:=1000

ServiceUnavailableException after timeout 19

OSGi – CDI (Contexts and Dependency Injection)

Draft RFC-193 no implementation yet

https://speakerdeck.com/paulbakker/rfc-193-osgi-cdi - Luminis Tech.

@OSGIComponent

public class MyComponent {

@Inject

@OSGiService(required=false)

MyService myService;

}

Service dynamics

Injection happens every time MyService is registered/deregistered

With required=true MyCOmponent is deregistered when MyService is not available

Declarative service listeners @ServiceAdded, @ServiceRemoved

17

Core+ cache as external module - motivation

15

Core+ cache as external module - overview

15

Embedded Felix. Separate Spring context. Service Proxy. Cache Client. API is a bundle.

Core+ cache as external module - demo

Architecture

• embedded Felix OSGi container

• Spring context startup in bundle activator

• OSGi Service proxy – can act as proxy over any protocol

• Possibility to run without OSGi

• Cache checker

Features

• No thigh coupling to OSGi

• Connect client to service without OSGi (direct spring)

• Incremental migration to OSGi

Life demo

• Start/stop bundle

• How application reacts

10

OSGi readings

Building Modular Cloud Apps with OSGi

Paul Bakker

8

OSGi conference

Never A Wrong (Semantic) Version Again! http://youtu.be/LBgNRsEJCWo

DS, BP, EJB, CDI, WTF!? http://youtu.be/wr85daWNpZo

Testing OSGi the "groovy" way http://youtu.be/UEWIoyIvT3Y

Continuous Automated Deployment with Apache ACE

http://www.slideshare.net/mfrancis/continuous-automated-deployment-with-apache-ace-jago-de-vreede-marcel-offermans

More: http://www.osgi.org/CommunityEvent2013/Schedule

6

Questions