OSGi for Enterprises by Holger Hoffstätte & Robert Dunne (Paremus) at OSGi Users Forum UK, 23rd Nov 2010.

1. www.paremus.com
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Transforming the Way
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Copyright © 2010 Paremus Ltd. May not be reproduced by any means without express permission. All rights reserved.
Paremus Nov 2010
OSGi For Enterprises
Holger Hoffstätte
holger.hoffstatte@paremus.com
Robert Dunne
robert.dunne@paremus.com
The new Nimble Distribution with RSA
Available in December
http://nimble.paremus.com/distribution
Video Podcast available - http://skillsmatter.com/podcast/java-jee/osgi-for-enterprises/rl-311

2. www.paremus.com
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Transforming the Way
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Copyright © 2010 Paremus Ltd. May not be reproduced by any means without express permission. All rights reserved.
Paremus Nov 2010
Agenda
• Demo Technology Overview
• Local Demo Walkthrough
• OSGi Remote Services (Holger)

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Transforming the Way
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Technologies
• OSGi
• Scala + Lift
• HTML + CSS + Javascript (JQuery)

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Transforming the Way
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Build Tools
• Bnd
• Eclipse PDE
• Apache Sigil
• Tycho
• Bndtools

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Transforming the Way
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Nimble
• OSGi Distribution
• Posh: Bash like shell for OSGi based on Apache Gogo
• Nimble Resolver: APT like installation system for OSGi

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Transforming the Way
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Declarative Services
• Dynamic Dependency Injection & Service Publication
• Reduce Accidental Temporal Dependencies
• Increase Resilience

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Transforming the Way
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Configuration Admin
• Modular, Dynamic Configuration & Reconfiguration
• PIDs: Named Property lists
• Integrates with Declarative Services

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Transforming the Way
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OSGi Remote Services
A Flexible Foundation for
Composite Applications

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Transforming the Way
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Paremus Nov 2010
Who am I?
• Holger Hoffstätte (aka @asynchronaut)
Living & working in Germany, near Cologne
• Consulting Engineer for Paremus Ltd.
Working on next-generation Service Fabric product line
• >20 years experience with concurrent/distributed systems, incl.Agile/
Process coaching,AOP, B2B, Enterprise Integration etc.

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Transforming the Way
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Copyright © 2010 Paremus Ltd. May not be reproduced by any means without express permission. All rights reserved.
Paremus Nov 2010
What's this about?
• OSGi & Remote Services:
Motivation & History
• Overview of Remote Services/RSA Specifications
• Applicability & Use Cases
→ little to no code!

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Transforming the Way
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Paremus Nov 2010
OSGi = SOA!
• Physical and logical isolation of Bundles
• Bundle Wiring with dynamic behaviour
• Service registration, discovery & matching
• Lifecycle control
• In R4.2: scoped visibility of services & events

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Transforming the Way
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Copyright © 2010 Paremus Ltd. May not be reproduced by any means without express permission. All rights reserved.
Paremus Nov 2010
Systems Hygiene:
simply a good idea
“The ability of OSGi to handle
complex systems as a set of
interdependent modules is kind of
like toilet paper: Sooner or later,
you're going to want to use it.”
– Hal Hildebrand

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Paremus Nov 2010
..but what about Distributed
Systems?

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..hmm..why not..
“Just use RMI or EJB!
It's built-in and Standard!”
– your local Architecture Astronaut
...ooomphh →

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/**
* Implementation of ICustomRemote Interface.
*/
public class CustomRemoteImpl extends UnicastRemoteObject implements ICustomRemote {
/**
* Necessary because Super-Class constructor throws RemoteException.
* @throws java.rmi.RemoteException Will be thrown if there are some network
* errors.
*/
public CustomRemoteImpl() throws RemoteException {
}
/**
* Returns a string which say 'Hello World with RMI.'
* @return the string which holds the value.
* @throws java.rmi.RemoteException Will be thrown if there are some network
* problems.
*/
public String sayHello() throws RemoteException {
return "Hello World with RMI.";
}
} :-(

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Transforming the Way
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Copyright © 2010 Paremus Ltd. May not be reproduced by any means without express permission. All rights reserved.
Paremus Nov 2010
..hmm..why not..
“We should just use JMS or our
Enterprisey 'Service Bus' for
everything!”
– probably someone on your team
..alrighty then.. →

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Paremus Nov 2010
..hmm..why not..
“I know!We can simply write our
own RPC library over sockets! It's
so easy! I did that back in Uni!”
– your “Rock Star” intern
..oh noes! →

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Transforming the Way
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Copyright © 2010 Paremus Ltd. May not be reproduced by any means without express permission. All rights reserved.
Paremus Nov 2010
Sad Reality
• Any kind of distribution often still hardwired into “stuff”
(and nobody really understands how it works..or wants to)
• System evolution often burdened with architectural decisions at the wrong
time of the development cycle:
• Distribution features added either “too early” or “too late”
• Negatively impacts time-to-feature & subsystem/integration testing
• Iterations increasingly resemble wading through mud
that keeps getting deeper

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Transforming the Way
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Copyright © 2010 Paremus Ltd. May not be reproduced by any means without express permission. All rights reserved.
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Silver Lining?
• Previous attempts:
Tuscany SCA, R-OSGi, Newton..
• All have more or less similar
ideas: composite applications,
distributed wiring..
• All more or less incompatible with
each other and/or “standard” OSGi

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Transforming the Way
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Key Realizations
• Distributed systems need adaptability for ALL aspects:
development, testing, deployment, runtime, maintenance
• No Silver Bullet/Golden Hammer possible:
too many contradicting requirements like
availability, cost, licensing, interop, latency, knowledge, security..

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Transforming the Way
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Copyright © 2010 Paremus Ltd. May not be reproduced by any means without express permission. All rights reserved.
Paremus Nov 2010
Standardize interaction,
not features!
• Allow multiple implementations using different technologies
side-by-side
• Prevent “Golden Hammer Syndrome”:
don't force choice of one technology for every kind of interaction, even
when inappropriate

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Transforming the Way
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Paremus Nov 2010
Consequences
• Almost-transparent extension of the OSGi service model:
no explicit infrastructure API in “user code”!
• No mandated use of SOAP/RMI/HTTP/JMS/etc.:
choice of technology can be driven by requirements
• anything that moves bytes from A to B should be usable
as transport!

23. www.paremus.com
www.paremus.com
Transforming the Way
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Copyright © 2010 Paremus Ltd. May not be reproduced by any means without express permission. All rights reserved.
Paremus Nov 2010
OSGi EEG to
the Rescue!
• Definition of Remote Services in OSGi R4.2
• Two minimalistic specs that accommodate each other:
• Remote Services: the “mechanics” of transports
• Remote Service Admin: standardized discovery &
import/export visibility control

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Transforming the Way
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Copyright © 2010 Paremus Ltd. May not be reproduced by any means without express permission. All rights reserved.
Paremus Nov 2010
Remote Services

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Transforming the Way
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Paremus Nov 2010
Remote Services
• Standardized Service Properties define the interaction between
participants
• Abstract “Intents” specify context-dependent “required vs. provided”
capabilities; matched by standard OSGi filters
• Flexible configuration: properties, code, vendor-specific..

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Transforming the Way
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Copyright © 2010 Paremus Ltd. May not be reproduced by any means without express permission. All rights reserved.
Paremus Nov 2010
Remote Services
Easier cross-platform
integration for OSGi!
ProtocolBuffers,Thrift,
JSON-RPC,Avro..

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Transforming the Way
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Paremus Nov 2010
Remote Service Admin

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Transforming the Way
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Remote Service Admin
• RSA itself merely an abstract control interface for implementors,
usually the vendor of a distribution provider
• Discovery providers discover/announce services on the network
• “Topology Manager” controls import/export visibility;
specifics left to implementation → innovation!

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Transforming the Way
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Copyright © 2010 Paremus Ltd. May not be reproduced by any means without express permission. All rights reserved.
Paremus Nov 2010
Discovery
• Discovery providers are simply “EndpointListeners”
that map a specific service announcement to & from a
standardized “EndpointDescription”
• Can use any mechanism that can store & update
service state/visibility
• Obvious candidates: SLP, DNS-SD, Data Distribution Service,
Apache Zookeeper, RDBMS, Data Grids, P2P Systems, DHTs..

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Transforming the Way
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Copyright © 2010 Paremus Ltd. May not be reproduced by any means without express permission. All rights reserved.
Paremus Nov 2010
Sounds awesome!

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Transforming the Way
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Copyright © 2010 Paremus Ltd. May not be reproduced by any means without express permission. All rights reserved.
Paremus Nov 2010
..but not so fast!
• Service interactions defined by Java interface
– well-understood :-)
– not very flexible :-(
• Fundamental limits to what can be
expressed with a synchronous RPC model
• Fallacies of Distributed Computing etc.

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Transforming the Way
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Copyright © 2010 Paremus Ltd. May not be reproduced by any means without express permission. All rights reserved.
Paremus Nov 2010
Problems with RPC
• Lack of reliability necessitates Fault Detection (active & passive)
• Call-by-reference vs. Call-by-value:
impact on interaction semantics that cannot be ignored
• Latency spikes will introduce strong variance in perceived behaviour
• Variance adds up if remote services are chained

33. www.paremus.com
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Transforming the Way
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Copyright © 2010 Paremus Ltd. May not be reproduced by any means without express permission. All rights reserved.
Paremus Nov 2010
OSGi helps!
• Can't fix the network, but does help with „unexpected“ faults:
org.osgi.framework.ServiceException extends RuntimeException
• Service are expected to be dynamic – no change! :-)
• What changes is the scope of a disappearing service -
...but does that really matter? Gone is gone!

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Transforming the Way
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Copyright © 2010 Paremus Ltd. May not be reproduced by any means without express permission. All rights reserved.
Paremus Nov 2010
Actual Benefits (1)
• Isolate that special third-party native code that keeps crashing
your entire JVM
• Operational isolation through service visibility policies
→ smaller/faster test cycles → faster time-to-feature
→ no accidental crosstalk between development teams
→ runtime: security, confidentiality..

35. www.paremus.com
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Transforming the Way
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Copyright © 2010 Paremus Ltd. May not be reproduced by any means without express permission. All rights reserved.
Paremus Nov 2010
Actual Benefits (2)
• Ops teams usually more open to dynamic updates of isolated services in
separate processes – much easier now
• Service Migration on host downtime
→ switching services much faster than host recovery/reboot
• Service selection based on cost/performance/latency..
→ finally a good reason to do proper end-to-end system design :)

36. www.paremus.com
www.paremus.com
Transforming the Way
the World Runs Applications
Copyright © 2010 Paremus Ltd. May not be reproduced by any means without express permission. All rights reserved.
Paremus Nov 2010
Implementations
RSA Reference Implementation using Apache
CXF and Zookeeper
Built on Eclipse Communication Framework
Based on RI but rewritten for correctness, extensibility, RSA
compliance. Basis for commercial product.
Built with Tuscany/SCA?

37. www.paremus.com
www.paremus.com
Transforming the Way
the World Runs Applications
Copyright © 2010 Paremus Ltd. May not be reproduced by any means without express permission. All rights reserved.
Paremus Nov 2010
Thank You
Holger Hoffstätte
holger.hoffstatte@paremus.com
Robert Dunne
robert.dunne@paremus.com
The new Nimble Distribution with RSA
Available in December
http://nimble.paremus.com/distribution