Enterprise OSGi 4.2 standardized the use of a number of component models for developing Enterprise OSGi applications: Servlet, JSP, Blueprint, and JPA. Implementations of these specifications have since become available in many open source projects and products such as Apache Aries, Eclipse Gemini/Virgo, GlassFish, JBoss Application Server and WebSphere Application Server. Looking at a number of these environments, it's clear that when it comes to assembly and deployment there's still something missing, namely something to represent a collection of bundles (e.g. an Application). Eclipse Virgo has "PARs" and "Plans", Apache Aries has "Applications", and WebSphere Application Server has “Applications” and “Composites”. Looking further afield to kernel projects, other bundle collection concepts exist, such as Apache Karaf "Features". Each model has concepts in common, such as identity, versioning and content, but also differences like isolation and format. It is clear that this is an area of Enterprise OSGi that could benefit from standardization and hence the Subsystems specification is being created. Subsystems is currently a draft specification which is standardizing artefacts representing collections of bundles, such as an Application. This presentation will introduce the current Subsystems design. It will describe how Subsystems can be used for development and deployment of bundle collections with different isolation semantics, to address the application, composite and feature use cases seen in the OSGi community today.

1. Subsystems:
for those occassions where bundles are just too small
Graham Charters
IBM
21st September 2011
OSGi Alliance Marketing © 2008-2010 . 1
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2. Disclaimer
• Subsystems is an in-progress RFC. What follows is a
snapshot in time of the expert group thinking and is
subject to change.
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3. Agenda
• Motivation
• Model
• Development Meta-data
• Deployment Meta-data
• Packaging
• Life-cycle
• API
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4. Motivation
• Enterprise Java platforms are awash with bundle
collections
• Apache Aries – Applications
• Apache Geronimo - Applications
• Apache Karaf – Features
• Eclipse Virgo – Plans, PARs
• IBM WebSphere Application Server – Applications
and Composite
• Oracle GlassFish – Applications
• Paremus Service Fabric – Systems
• Crying out for standardization
• Portability
• Tools
• Ecosystem
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5. Subsystems Model: Hierarchy
• Most common model is subsystem
hierarchy and so
Subsystems are no subsystem
different
• Each has 1 parent subsystem
• Each can have many children
subsystem subsystem
• Children of the same parent
are siblings
• Visually represented by subsystem subsystem
containment
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6. Subsystem Model: Sharing Policies
• Subsystems may provide and consume capabilities
• E.g. packages, services, etc…
• Different subsystem types have different default sharing
policies
• E.g. share everything, share nothing, provide nothing
• Subsystem types that provide isolation may also have
affinity – i.e. prefer the capabilities of their contents
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7. Feature Subsystems
feature
bundle
• Collection of Resources
(e.g. Bundles) feature
• Shared life-cycle bundle
• Can be nested
• No isolation or affinity bundle
• Repository-based bundle
provisioning
• Examples: Karaf
Features, Virgo unscoped
Plans bundle bundle
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8. Composite Subsystems
• Coarse-grained sub- bundle
assembly module
• Isolated composite
• Explicit share in/out
bundle
• Affinity
bundle
• Repository-based
provisioning bundle
• Examples: RFC 138
Composite Bundles*,
WebSphere Composite
bundle bundle
Bundles
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*old design prior to resolver hooks

9. Application Subsystems
• Model for hosted
applications
• Isolated application
bundle
• No sharing out, implicit
sharing in bundle
• Affinity
bundle
• Repository-based
provisioning
• Examples: Aries
bundle bundle
Application, Virgo Scoped
Plans, Virgo PARs
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10. Example Combination
• Subsystem Types can be
mixed ‘n’ matched framework
• Example shows: application application
• Features used to assemble a
Composite
• Composite providing a ‘platform’ to
composite
Applications
feature feature
feature
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11. Developer Headers
• Manifest format with relaxed rules
• Common concepts use same headers
• Some headers unique to Subsystem type
• Headers cover:
• Identity
• Content
• Isolation policy
• Human readable information
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12. Identity Headers
• Identified by symbolic
name and version Manifest-Version: 1.0
Subsystem-ManifestVersion: 1.0
• All subsystem types Subsystem-SymbolicName:
my.first.subsystem
live in the same Subsystem-Version: 1.0.0
namespace so type
not part of the identity
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13. Type Header
• Type governs the sharing policy
• Standard Types:
Manifest-Version: 1.0
• osgi.application (the default) Subsystem-ManifestVersion: 1.0
• osgi.composite Subsystem-SymbolicName:
my.first.subsystem
• osgi.feature Subsystem-Version: 1.0.0
Subsystem-Type:
• All subsystem types live in osgi.application;
same resource type provision-policy:=acceptTransitive
(osgi.subsystem), so their
subsystem type is not part of
their identity
• One directive used in
provisioning (see later)
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14. Content
• Identifies the resources
contained in the Subsystem Manifest-Version: 1.0
Subsystem-ManifestVersion: 1.0
• Resources identified by name, Subsystem-SymbolicName:
my.first.Subsystem
version (range) and type Subsystem-Version: 1.0.0
• Composites only allow fixed Subsystem-Type:
versions osgi.application;
provision-policy:=acceptTransitive
• Standard types Subsystem-Content:
an.osgi.bundle1;version="[1.0, 1.1)",
• osgi.bundle (default) an.osgi.subsystem;
• osgi.subsystem type:=osgi.subsystem;
version="[1.2, 1.3)",
• osgi.configuration* an.osgi.config;
• Can be optional type:=osgi.configuration;
version="[1.0, 1.1)";
resolution:=optional
*if we get there…
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15. Informational
Manifest-Version: 1.0
• Headers for humans Subsystem-ManifestVersion: 1.0
Subsystem-Name: First Subsystem
• Localized just like bundles Subsystem-Description:
This is my first ever Subsystem and
it's sooo cool.
Subsystem-SymbolicName:
my.first.subsystem
Subsystem-Version: 1.0.0
Subsystem-Type:
osgi.application;
provision-policy:=acceptTransitive
Subsystem-Content:
an.osgi.bundle;version="[1.0, 1.1)",
an.osgi.subsystem;
type:=osgi.subsystem;
version="[1.2, 1.3)",
an.osgi.config;
type:=osgi.configuration;
version="[1.0, 1.1)"
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16. Explicit Sharing Manifest-Version: 1.0
Subsystem-ManifestVersion: 1.0
Subsystem-Name: A Composite Subsystem
Subsystem-Description:
This is a Composite Subsystem
Subsystem-SymbolicName:
my.first.composite
Subsystem-Version: 1.0.0
• Composite subsystems Subsystem-Type: osgi.composite
Subsystem-Content:
share nothing unless an.osgi.bundle1;version="[1.0, 1.0]",
explicitly stated an.osgi.bundle2;version="[1.0, 1.0]"
Subsystem-ExportService:
• Re-use existing bundle exported.service.Interface;
headers where applicable filter:="(color=blue)"
Subsystem-ImportService:
• Not applicable for implicitly imported.service.Interface
isolated subsystems (i.e. Export-Package:
an.exported.pkg;version="1.0"
Features and Import-Package:
Applications) an.imported.pkg;version="[1.0, 2.0)"
Require-Bundle:
a.required.bundle;
bundle-version="[1.0, 2.0)"
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17. Locking down deployment
• Subsystem manifest allows version variability
• Enables flexibility during development
• Bounds operational upgrade
• Desirable to lock down versions during QA
• Carry same deployment from testing to production
• Deployment Manifest
• Locks down contents to specific versions
• Identifies supporting transitive dependencies
• Describes package/service import/export details
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18. Deployment Manifest
DESCRIPT’N SUBSYSTEM.MF DEPLOYMENT.MF
Boilerplate Manifest-Version: 1.0 Manifest-Version: 1.0
Subsystem-ManifestVersion: 1.0 Deployment-ManifestVersion: 1.0
Identity + Subsystem-SymbolicName: Subsystem-SymbolicName:
Subsystype my.first.subsystem my.first.subsystem
Subsystem-Version: 1.0.0 Subsystem-Version: 1.0.0
Subsystem-Type: osgi.application
Content Subsystem-Content: Deployed-Content:
an.osgi.bundle;version="[1.0, 1.1)", an.osgi.bundle;type:=osgi.bundle;
an.osgi.subsystem;type:=osgi.subsystem; deployed-version=1.0.0,
version="[1.2, 1.3)", an.osgi.subsystem;type:=osgi.subsystem;
an.osgi.config;type:=osgi.configuration; deployed-version=1.2.0,
version="[1.0, 1.1)"; an.osgi.config;type:=osgi.configuration;
resolution:=optional deployed-version=1.0.5
Transitive <Only part of the deployment> Provision-Resource:
Dependencies an.osgi.bundle2;type:=osgi.bundle;
deployed-version=1.0.0
an.osgi.bundle3;type:=osgi.bundle;
deployed-version=1.0.0
Sharing Policy <Implicit for Application Subsystems> Deployed-ServiceImport:
(objectClass=an.osgi.Service)
Import-Package:
a.pkg;version="1.0.0",
a.pkg2;version="1.4"
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19. Manifest-Version: 1.0
Example
Deployment-ManifestVersion: 1.0
Subsystem-SymbolicName:
my.first.subsystem
Subsystem-Version: 1.0.0
Deployed-Content:
an.osgi.bundle;type:=osgi.bundle;
deployed-version=1.0.0, application
an.osgi.subsystem;type:=osgi.subsystem;
deployed-version=1.2.0,
an.osgi.config; config subsystem
type:=osgi.configuration;
deployed-version=1.0.5
Provision-Resource:
an.osgi.bundle2;type:=osgi.bundle; bundle
deployed-version=1.0.0
an.osgi.bundle3;type:=osgi.bundle;
deployed-version=1.0.0 Service pkg pkg2
Deployed-ServiceImport:
(objectClass=an.osgi.Service)
Import-Package:
a.pkg;version="1.0.0", bundle3 bundle2
a.pkg2;version="1.4"
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20. Transitive
Subsystem-Type: osgi.composite;
Dependencies provision-policy:=acceptTransitive
Subsystem-Type:
• Provision-Resource identifies osgi.application
resources to be provisioned in
Subsystem-Type:
support of a Subsystem config osgi.composite
• A Subsystem can choose to accept
transitive dependencies from itself
and its children bundle
Subsystem-Type: osgi.composite;
provision-policy:=acceptTransitive
Service pkg pkg2
• The Root Subsystem always
accepts transitive dependencies
• Sharing policies need to be correct bundle3 bundle2
to ensure children can see their
transitive dependencies
Transitive Dependencies
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21. Portability
• Subsystem Manifests are
portable to a point
• Target Environment +
Subsystem Definition
Transitive Dependencies must
support the required resource
implementation types (e.g. Transitive
Blueprint, WAB, DS, etc) Dependencies
• Deployment manifests may
be portable Target Environment
• Different Target Environments
likely to require different
Transitive Dependencies
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22. Packaging
• Packaged in a Subsystem my.first.subsystem.ssa
Archive
• A zip file with .ssa OSGI-INF/SUBSYSTEM.MF
extension: OSGI-INF/DEPLOYMENT.MF
• Subsystem Manifest
(optional)
an.osgi.bundle-1.0.0.jar
• Deployment Manifest
(optional) an.osgi.bundle2-1.0.0.jar
• Resources
(optional)
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23. Life-cycle
install
INSTALLING
• Life-cycle similar to that of
INSTALLED UPDATING
bundles update
resolve
• Adds ‘transitional states’
uninstall
to reflect periods where RESOLVING
STARTING
contents are in process of
changing state RESOLVED ACTIVE
uninstall
• E.g. INSTALLING, stop
RESOLVING, …
STOPPING
UNINSTALLIN
G
UNINSTALLED
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24. Shared resource life-cycle
• Resources may be shared
between Subsystems
• Intersecting Features
ACTIVE
• Common transitive
dependencies
• Shared resource states
determined by states of RESOLVED
Subsystems that depend on
them
• State precedence used to INSTALLED
determine shared resource state
• Highest state wins
• All uninstalled == garbage
UNSTALLED
collection
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25. Application Subsystem
Example installed and resolved
Composite ACTIVE
Application RESOLVED
bundle
RESOLVED
transitive bundle
RESOLVED
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26. Second Application
Example Subsystem installed and
started
Composite ACTIVE
Application RESOLVED Application ACTIVE
bundle bundle
RESOLVED ACTIVE
transitive bundle transitive bundle
ACTIVE ACTIVE
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27. Second Application
Example Subsystem uninstalled
Composite ACTIVE
Application RESOLVED Application UNINSTALLED
bundle bundle
RESOLVED UNINSTALLED
transitive bundle transitive bundle
RESOLVED UNINSTALLED
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28. First Application Subsystem
Example uninstalled
Composite ACTIVE
Application UNINSTALLED Application UNINSTALLED
bundle bundle
UNINSTALLED UNINSTALLED
transitive bundle transitive bundle
UNINSTALLED UNINSTALLED
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29. Subsystem Service
• Each subsystem framework
logically has it’s own application
Subsystem service
• An environment can choose to
hide for certain subsystems
composite
• Life-cycle management
• Install, start, stop, uninstall, feature feature
cancel
• Navigation feature
• getParent, getChildren,
getConstituents
• Introspection
• getHeaders, getState,
getSymbolicName, getVersion,
getLocation
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30. Summary
• Subsystems are the standard way to manage groups of
resources
• Version ranges allow flexibility in resource selection
• Subsystem types define sharing semantics
• Deployment definition
• locks down versions and sharing
• Identifies transitive dependencies
• API enables management of Subsystem life-cycle
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31. Trademarks
IBM and WebSphere are trademarks or registered trademarks of
International Business Machines Corp., registered in many
jurisdictions worldwide.
Java and all Java-based trademarks and logos are trademarks or
registered trademarks of Oracle and/or its affiliates.
Other product and service names might be trademarks of IBM or other
companies. A current list of IBM trademarks is available on the Web at
“Copyright and trademark information” at
www.ibm.com/legal/copytrade.shtml.
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