Chapter 4.2 - Draft, Verse 138 :
The Framework Multiplication
Clement Escoffier, akquinet A.G.

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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
 MobileDevices, 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)
3 The Framework Multiplication

Why multiple OSGi frameworks
in one VM ?
 OSGi has made a successful
breakthrough Bundle
(packaging and Service binding
 THE module layer on the top of deployment unit) (loose-coupled,
Java dynamic)
 Wide spread usages as
middleware kernel
 Mobile devices
 Desktop applications
 Lightweight Application servers
 Enterprise Application Servers
 More and more used by OSGi™ framework
application themselves
 Modularity Java Virtual Machine
 Dynamism
 Provisioning
4 The Framework Multiplication

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
Java Virtual Machine
5 The Framework Multiplication

Why ? – Application Model
composite {
 Creation of composite
Install-Bundle:
 Deployment packages++ foo; bundle-version=[1.0.0,1.2.0),
bar; bundle-version=[1.0.0,1.0.0]
 Allows to describes Import-Package: waz; version=2.0.0
applications Export-Package: baz; version=1.0.1
}
Exemple
 Such composites should
be ran in an isolated child
framework
Child framework
OSGi™ framework
Java Virtual Machine
6 The Framework Multiplication

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
7 The Framework Multiplication

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)
FWK 1 FWK 2
Launcher
Java Virtual Machine
8 The Framework Multiplication

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….
OSGi Framework
Bundle
OSGi Framework
Java Virtual Machine
9 The Framework Multiplication

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
10 The Framework Multiplication

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
11 The Framework Multiplication

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
12 The Framework Multiplication

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
13 The Framework Multiplication

The parent – child relationship
 Child
frameworks
managed by
 A composite bundle Child Framework
 Representing the child into
the parent Surrogate
Bundle
 A surrogate bundle
 Representing the parent into
the child
Composite
Bundle
OSGi Framework
Java Virtual Machine
14 The Framework Multiplication

Surrogate & Composite Bundles
 The Surrogate represents the parent framework into the
child framework
 Publishes imported services into the child service registry
 Exports imported packages
 TheComposite represents the child framework into the
parent framework
 Publishes exported services into the parent service registry
 Exports exported packages
15 The Framework Multiplication

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
16 The Framework Multiplication

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…
17 The Framework Multiplication

Conclusion
 Beingable 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…
18 The Framework Multiplication

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
19 The Framework Multiplication

Questions ?
Karl Pauls Dr. Clement Escoffier
karl.pauls@akquinet.de clement.escoffier@akquinet.de
Bülowstraße 66, 10783 Berlin Bülowstraße 66, 10783 Berlin
+49 151 226 49 845 +49 175 2467717
20 The Framework Multiplication