the osgi framework multiplication

Chapter 4.2 - Draft, Verse 138 : The Framework Multiplication

Clement Escoffier, akquinet A.G.

akquinet

Partner Power International GmbH Partnerbeteiligung

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In association 2007

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International

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Microsoft / .NET

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2 The Framework Multiplication

Modular and Mobile Solutions Competence Center focusing on

Modular Systems Modularization expertise OSGi-based Sophisticated, Large scale, Distributed systems

Mobile Solutions In the large

Mobile Devices, Interactions middleware, Server-side … M2M, Data collection and Mediation, Control loop

Technologies iPHONE / Android OSGi (Apache Felix, Apace Ace, OW2 Chameleon, Apache Sling…) Java EE (JBOSS, OW2 JOnAS)


Why multiple OSGi frameworks in one VM ? OSGi has made a successful

breakthrough THE module layer on the top of

Java

Wide spread usages as middleware kernel Mobile devices Desktop applications Lightweight Application servers Enterprise Application Servers

More and more used by application themselves Modularity Dynamism Provisioning

Java Virtual Machine

OSGi™ framework

Bundle (packaging and

deployment unit) Service binding (loose-coupled,

dynamic)


Why ? - Runtime/ Application isolation

Conflicts ! Internal / Private API

exposed by the middleware used unexpectedly by the applications

Version conflict on third-party libraries


OSGi™ framework


Why ? – Application Model Creation of composite

Deployment packages++ Allows to describes

applications

Such composites should be ran in an isolated child framework

composite {

Install-Bundle: foo; bundle-version=[1.0.0,1.2.0), bar; bundle-version=[1.0.0,1.0.0] Import-Package: waz; version=2.0.0 Export-Package: baz; version=1.0.1 }

Exemple


OSGi™ framework

Child framework


Why ? – Avoid applications conflicts Same issues as the middleware /applications conflicts

Two applications may share services But sometimes …. NOT ! Stateful services

Third-party library conflicts

By using separate frameworks Guaranty a service isolation Guaranty a third-party libraries isolation


How do we solve that today ? The Launcher approach

OSGi R4.2 has standardized how to create OSGi framework instances Framework Factory

factory.newFramework(config)


Launcher

FWK 1 FWK 2


How do we solve that today ? The Child approach

A bundle instantiates a new OSGi framework The lifecycle of this framework is managed by the bundle Relationships between the intra-bundle and the external world

are managed by the bundle May be tricky….


Bundle

OSGi Framework

OSGi Framework


Does this work ? In simple cases … YES In sophisticated cases …. Absolutely NO

Cross-framework singleton bundle ? A singleton bundle may be resolved several times on the JVM

URL Streams have to be multiplexed The JVM supports only ONE extension of the URL class What happens if several framework provide several times the same URL

Handler ?

The Security Manager is a JVM Singleton The condition permission admin directly uses the JVM security

No way to adapt the security policy per framework


The RFC 0138 Multiple Frameworks In One JVM

OSGi R4.2 RFC

Not pushed in the OSGi R4.2 because of some direct impacts on the framework Will be somewhere in OSGi R5

Assumption Each framework manages its own class space, and is responsible for

managing the lifecycle and resolution of its bundles. Class reachability inside the framework is managed by bundle resolution

and classloading rules Class reachability outside the framework is managed by standard

classloading rules and hierarchies


Child Framework Define a way to create child frameworks

Created thanks to a Framework service (CompositeBundleFactory)

Similar to the Launcher API Framework configuration Composite Manifest


Composite Manifest A Composite Manifest may contain

Bundle-Version and Bundle-SymbolicName Import-Package from the parent framework Export-Package from the child to the parent CompositeServiceFilter-Export

Exports services from the child to the parent Equivalent to iPOJO exports

CompositeServiceFilter-Import Imports a service from the parent to the child Equivalent to iPOJO imports

No way to install bundles directly in the composite At least in the last version of the RFC Allows to define your ADL, to choose your provisioning mechanism... Can be done with the framework configuration map


The parent – child relationship Child frameworks

managed by A composite bundle

Representing the child into the parent

A surrogate bundle Representing the parent into

the child


OSGi Framework

Child Framework

Composite Bundle

Surrogate Bundle


Surrogate & Composite Bundles The Surrogate represents the parent framework into the

child framework Publishes imported services into the child service registry Exports imported packages

The Composite represents the child framework into the parent framework Publishes exported services into the parent service registry Exports exported packages


Singleton Multiplexing Propose a way to multiplex URL Handler without

conflicts

Objective Resolve URL by using the ‘adequate’ URL Handler Already done inside Felix

Analyze from the stack trace which Framework triggers the URL resolving

Use the good URL Handler service


What else ?

…

RFC not included into OSGi R4.2 Break the system bundle lifecycle (RESOLVED state ?)

Impact the core specification

Surrogate bundles are complex Why not reusing the System Bundle ?

The specification does not cover all use cases Security ? Others singletons ?

However, it’s still a work in progress…


Conclusion Being able to launch several frameworks inside the same

VM is definitely required But it’s not so simple !

The RFC 0138 proposes a first draft addressing the issues Child framework creation and management Singleton multiplexing

However, it’s far from complete And complex to implement…


What might be cool A real composite bundle description language

ADL Abstract placeholder

Dynamism, Substitution

Creating a bridge with the deployment admin A deployment package could create a child framework

Sandbox mechanism Like on the iPHONE


Questions ?

The Framework Multiplication 20

Karl Pauls [email protected] Bülowstraße 66, 10783 Berlin +49 151 226 49 845

Dr. Clement Escoffier [email protected]

Bülowstraße 66, 10783 Berlin +49 175 2467717

the osgi framework multiplication

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