services first migration to osgi - osgi users forum uk 16-nov2011

Services-First Migration to OSGi

BJ Hargrave (IBM)Peter Kriens (aQute)

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Agenda

• Modularity Maturity Model

• The Brick Wall

• Couplings

• µServices

• What Broker?

• Example

• Conclusion

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Modularity Maturity Model

• 1 Ad Hoc

• 2 Managed

• 3 Contracts

• 4 Fences

• 5 Optimize

Page 2 OSGi Alliance Marketing © 2008-2011 . All Rights Reserved, © IBM Corp. 2011

21.09.2011

Inspired by Graham Charters’ excellent OSGi Community Event 2011 presentation @ http://slidesha.re/q8EHFp

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Modularity Maturity Model

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1. Ad Hoc• Flat, manual class path

• Single name space

• Full visibility and normal accessibility

• Monolithic

• Highly coupled

• Split Packages

• Add/Shuffle JARs until it works

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1. Ad Hoc• Flat, manual class path

• Single name space

• Full visibility and normal accessibility

• Monolithic

• Highly coupled

• Split Packages

• Add/Shuffle JARs until it works

JAR H

ell

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2. Managed

• Treat JARs as a module

• JAR Identity

• Naming

• Versioning

• Dependencies

• Repositories

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2. Managed

• Treat JARs as a module

• JAR Identity

• Naming

• Versioning

• Dependencies

• Repositories

Down

load

the

inter

net

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3. Contracts

• Interface based design, POJOs

• Provide contracts for each connection between JARs

• Implementation details inside the JAR

• Versioning on contracts

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3. Contracts

• Interface based design, POJOs

• Provide contracts for each connection between JARs

• Implementation details inside the JAR

• Versioning on contracts

classloa

der

hacks

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4. Fences

• Explicitly Import/Export packages

• Explicitly specify requirements and capabilities

• Enforce the module boundaries

• Semantic Versioning

• Side-by-side versioning supported

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4. Fences

• Explicitly Import/Export packages

• Explicitly specify requirements and capabilities

• Enforce the module boundaries

• Semantic Versioning

• Side-by-side versioning supported

Good!

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5. Optimize• Exploit concepts for

modules and contracts

• Delegated Control

• Optimize the code base to leverage new patterns:

• Extender

• Whiteboard

• Repeat

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5. Optimize• Exploit concepts for

modules and contracts

• Delegated Control

• Optimize the code base to leverage new patterns:

• Extender

• Whiteboard

• Repeat

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Today1.

Ad Hoc

2.Managed

3.Contracts

4.Fences

5.Optimize

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Today1.

Ad Hoc

2.Managed

3.Contracts

4.Fences

5.Optimize

mvn

Ivy

jigsaw

guice

,CDI

sprin

g

Enterprise

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OSGi

Today1.

Ad Hoc

2.Managed

3.Contracts

4.Fences

5.Optimize

mvn

Ivy

jigsaw

guice

,CDI

sprin

g

Enterprise

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OSGi

Today1.

Ad Hoc

2.Managed

3.Contracts

4.Fences

5.Optimize

mvn

Ivy

jigsaw

guice

,CDI

sprin

g

Enterprise

4.Fences

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Class.forName(String)

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Class Space

class

package

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Class Space

class

package

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Class Space

class

package

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Class Space

V1 V2

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Class Space

V1 V2

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Class Space

V1 V2

Class.forName

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Class Space

V1 V2

xxClass.forName

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Class Space

V1 V2

xxClass.forName

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Why Class.forName?

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Why Class.forName?

COUP

LING!!!!!!!!!!!!!

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How to get an Instance?That is the Question!

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Couplings

modular not modular

Example

type FooImpl foo;

instanceFoo foo = (Foo) Class.forName(“FooImpl”) .newInstance();

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Type Couplingclass FooImpl{}class Client {}

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Type Couplingclass FooImpl{}class Client {}

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Type Couplingclass FooImpl{}

interface Foo{}

class Client {}

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Type Couplingclass FooImpl{}

interface Foo{}

class Client {}

uses implements

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Type Couplingclass FooImpl{}

interface Foo{}

class Client {}

uses implements

get instance

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Type Couplingclass FooImpl{}

interface Foo{}

class Client {}

uses implements

get instance

Contro

l

Issue

s?

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Instance Coupling

• New

• Factory

• Inversion of Control

• Broker

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Instance Coupling

• New

• Factory

• Inversion of Control

• Broker

implclient container

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Instance Coupling

• New

• Factory

• Inversion of Control

• Broker

implclient container

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Instance Coupling

• New

• Factory

• Inversion of Control

• Broker

implclient container

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Instance Coupling

• New

• Factory

• Inversion of Control

• Broker

implclient container

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Instance Coupling

• New

• Factory

• Inversion of Control

• Broker

implclient container

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µServices Primitive• Broker Pattern

• Direction

• Contract

• Publish

• Find

• Bind

• Who’s Listening?

• Cardinality

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µServices Primitive• Broker Pattern

• Direction

• Contract

• Publish

• Find

• Bind

• Who’s listening?

• Cardinality

BA S

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Patterns

• Factory

• Listener

• Discovery

• Distribution

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5. Optimize

E

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5. Optimize

D

A

G

B

E

H

C

F

I

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Back to the Brick Wall

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Migration

D

A

G

B

E

H

C

F

I

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Migration

D

A

G

B

E

H

C

F

I

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D

A

G

B

E

H

C

F

I

Migration

D

A

G

B

E

H

C

F

I

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D

A

G

B

E

H

C

F

I

Migration

D

A

G

B

E

H

C

F

I

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Migration

D

A

G

B

E

H

C

F

I

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So we need a broker that runs without

fences...

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So we need a Broker that runs without

Fences...

PojoSR

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POJOSR

• Developed by Karl Pauls

• JavaOne presentation 24811

• http://pojosr.googlecode.com

• Based on Apache Felix

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Gain• Existing libraries and many bundles work without

modification

• Bundle (JAR) activation (have their own local main)

• µServices

• Dynamicity (in µServices)

• Extender pattern (react on JAR content)

• Migration path to Fences (OSGi)

• Existing OSGi and non-OSGi tooling can be used

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Loss

• No dynamic install/uninstall/update

• No side-by-side versioning

• No module privacy

• No explicit dependencies

• No Lazy activation

• No Bundle classpath

• No Native Code support

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Migrating

• Example: extend ant … the tool we all (sometimes) love and (sometimes) hate

• We make different <helloXXX/> tasks

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Ant Your Service

• Base ant

• Activator

• Extenderant

......

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Ant Your Service

• Base ant

• Activator

• Extenderant

pojosrant

......

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Ant Your Service

• Base ant

• Activator

• Extenderant

......

pojosrant

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Ant Your Service

• Base ant

• Activator

• Extenderant

......

pojosrant

Class<Task>

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Ant Your Service

• Base ant

• Activator

• Extenderant

......

pojosrant

helloactivator

Class<Task>

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Ant Your Service

• Base ant

• Activator

• Extenderant

......

pojosrant

helloactivator

Class<Task>

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Ant Your Service

<project name="master">

<path id="bundles"> <fileset dir="bundles"> <include name="*.jar" /> </fileset> </path>

<taskdef name="auto" classname="aQute.ant.connect.AutoTask" classpathref="bundles" /> <auto />

<helloActivator />

</project>

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Ant Your Servicepublic class Activator implements BundleActivator {

public void start(BundleContext context) throws Exception { Properties props = new Properties(); props.put("ant", "helloActivator"); context.registerService(Class.class.getName(), HelloTask.class, props); }

public void stop(BundleContext context) throws Exception { }}public class HelloTask extends Task { String message = "Hello Activator"; public void execute() { System.out.println(message); } public void setMessage(String m) { this.message = m; }}

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Ant Your Servicepublic class Activator implements BundleActivator {

public void start(BundleContext context) throws Exception { Properties props = new Properties(); props.put("ant", "helloActivator"); context.registerService(Class.class.getName(), HelloTask.class, props); }

public void stop(BundleContext context) throws Exception { }}public class HelloTask extends Task { String message = "Hello Activator"; public void execute() { System.out.println(message); } public void setMessage(String m) { this.message = m; }}

cruft

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Ant Your Service

• Base ant

• Activator

• Extenderant

......

pojoant

helloactivator

Class<Task>

pojosrant

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Ant Your Service

• Base ant

• Activator

• Extenderant

......

pojoant

helloactivator

Class<Task>

pojosrant

helloextendee

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Ant Your Service

• Base ant

• Activator

• Extenderant

......

pojoant

helloactivator

Class<Task>

pojosrant

helloextendee

Manifest-Version: 1.0Ant-Task: helloExtender=HelloTask

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Ant Your Service

public class HelloTask extends Task { String message = "Hello Extender"; public void execute() { System.out.println(message); } public void setMessage(String m) { this.message = m; }}

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Ant Your Service

public class HelloTask extends Task { String message = "Hello Extender"; public void execute() { System.out.println(message); } public void setMessage(String m) { this.message = m; }}

NO cr

uft

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Conclusion

• Moving to Fences is hard because popular instance creation patterns are fundamentally not modular

• Services-First approach works without Fences

• After completion, moving to Fences is much easier

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Good FencesMake Good Neighbors

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Good FencesMake Good Neighborsmodules

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Q&A

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