Help me obr you are my only hope - osgi users forum uk 16-nov2011

Help Me OBR, You’re My Only Hope
David Savage
david.savage@paremus.com
Help Me OBR,You’re My Only Hope www.paremus.com November 2011
Copyright © 2011 Paremus Ltd. May not be reproduced by any means without express permission. All rights reserved.

Help Me OBR,You’re
My Only Hope
A Brief Introduction To The OSGi Bundle Repository


A Long Time Ago...

• OSGi Bundle Repository
• Motivation, History
• Main Aspects
• Beneﬁts, Impact on Ecosystem


Common OSGi Pain
Points


• Dependency Management:
• Development
• Deployment
• Runtime
• Which bundles to install when, why, how

The Story So Far...


• Informally speciﬁed & implemented by
Richard Hall ~2004, add-on to Felix


• Various problems:
• Provisioning external runtimes
• Distinction between development/
runtime


• Others:
• P2
• Nimble
• Sigil
• Maven
• Ivy

• Ofﬁcial OBR revived in 2009 by Hal
Hildebrand

• Spec'd by David Savage in EEG


The Problem


OBR Is...

• Primarily a standardised Model to describe:
• Which Bundles are available?
• What do they do?


OBR Is Not...

• A management agent/deployer:
• “calculator only”
• A “server” or “database”:
• no deﬁned protocol


Main Aspects

• Repository
• Resolver
• Interchange Format


A New Model

• Uses 4.3 concept of "wiring"
• Implements often requested functionality
for introspection


Environment

<<contains>>

<<expressed by>> <<provides>>
Resource

BundleRevision

<<connected by>> <<connected to>>
Requirement Capability

BundleRequirement Wire BundleCapability

BundleWire


• Resources can be
physical or virtual

• Resources have
Capability Requirement

Requirements and
Capabilities


• Capabilities have a
namespace and a
map of attributes
Capability Requirement

• Requirements have
a namespace and a
set of directives


• A Requirement
matches a Capability
if the namespaces
are equal and the
directives match the
attributes


Common Namespaces
• Capabilities:
• osgi.identity → Unique per resource
• osgi.content → Checksums, SCM, etc
• Requirements:
• osgi.wiring.package → Import-Package
• osgi.wiring.bundle → Require-Bundle

Repository

• Repository: simple
service(s) that
provide resources
with capabilities


Resolution

• Resources + Wiring A
B

C
D

= Environment
• Environment +
Requirements = D B

Resolution C A


An Example
osgi.service=servlet.container
effective=active
Active
Servlet
Servlet
Bundle
Container

Servlet
Container
Provider


Subsystems


Interchange Format

• Based on XML Schema
• Human-readable Name & URI for
repository identity
• Version increment (long)
• Resource URLs, Size, Checksums..

<?xml version=”1.0”?>
<repository name=”example” increment=”1”
targetNamespace=”http://www.osgi.org/xmlns/obr/v1.0.0”>
<resource>
<capability namespace=”osgi.identity”>
<attribute name=”osgi.identity” value=”org.foo.mumble” />
<attribute name=”version” type=”version” value=”1.0.0” />
<attribute name=”type” value=”osgi.bundle” />
</capability>
<capability namespace=”osgi.content”>
<attribute name=”osgi.content” value=”org/foo/
org.foo.mumble-1.0.0.jar” />
<attribute name=”size” type=”long” value=”46725” />
<attribute name=”checksum”
value=”1bafd2ece2e88db4cdf835a7f8f0de65fab5b1147977a5dcc59b7c1b8
c6f5080” />
</capability>
</resource>
</repository>


Leftovers

• Limited resolution failure introspection
• Repository event model
• License handling
• Web based service
• Deployment model → Subsystems

Conclusion

• OBR:
• Small, robust, reliable
• Fixes Things Automatically
• Gets The Job Done!


Questions?
• Email: david.savage@paremus.com

• Twitter: @davemssavage

• Blog: http://chronological-
thought.blogspot.com

• Book: http://www.manning.com/hall/

• Paremus: http://www.paremus.com

• OSGi: http://www.osgi.org


Help me obr you are my only hope - osgi users forum uk 16-nov2011

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