OSGi Remote Services with SCA using Apache Tuscany Raymond Feng rfeng@apache.org

OSGi Remote Services with SCA using Apache Tuscany

Raymond Feng

rfeng@apache.org

Agenda

• What are OSGi remote services?• A sample scenario: Distributed Calculator• Representing OSGi entities using SCA• Predefined mapping from OSGi to SCA• On-demand mapping from OSGi to SCA• Discovery of OSGi remote services• Demo of distributed calculator• Q&A

What are OSGi remote services?

OSGi local services

• The OSGi framework decouples service providers and consumers via a local service registry, where a service is an object that one bundle registers and another bundle gets.

• The services are only be accessed locally by bundles within the same framework instance. It would be nice to make them remote without significant changes of the programming model?

OSGi Remote Services

• The OSGi core framework specifies a model where bundles can use distributed services. (R4.2)

• The basic model for OSGi remote services is that a bundle can:– register services that are exported to a

communication endpoint – use services that are imported from a

communication endpoint (registering a proxy in local service registry)

OSGi Remote Services

NOTE: The diagram is copied from OSGi Service Platform Service Compendium R4.2 spec

Related OSGi specs

• OSGi Service Platform Release 4 Version 4.2 Compendium Specification – Chapter 13: Remote Services (PM, concepts and

properties)– http://www.osgi.org/download/r4v42/r4.cmpn.pdf

• Early Access draft of the OSGi 4.2 Enterprise Release – SCA Configuration Type (SCA specific properties)– Remote Service Admin (runtime architecture, SPIs)– http://www.osgi.org/download/osgi-4.2-enterprise-earl

y-draft4.pdf

SCA Configuration Type

• SCA Configuration Type for Remote Services– This chapter provides a standard mechanism

to configure Remote Services and provide qualities of service or intents, through SCA configuration metadata and WS-Policy. Remote Service implementations that also implement the SCA config type provide a portable way to configuration.

Remote Service Admin

• Remote Service Admin– This specification adds an extra layer on top of the existing

Remote Services spec (chapter 13 in the 4.2 Compendium). – The Distribution Provider registers a RemoteServiceAdmin

service that exports and imports services when asked. – The Discovery System API (EndpointListener) provides a

standard view over any Discovery System, regardless of how it's realized or what protocol it uses.

– The Topology Manager provides a Policy over these things. It decides what services will be exported and for when to look for services in a Discovery System.

OSGi remote services- A sample scenario

An OSGi based Calculator

Add

Service

Operations Bundle

Subtract

Service

Multiply

Service

Divide

ServiceCalculator bundle

Calculator

Service

OSGi service

OSGi service reference

Calculator

ServiceOSGi service interface

OSGi service implementation

Making the Calculator Distributed

• Run the calculator bundle and the operations bundle on two OSGi framework instances. – The calculator bundle registers the

CalculatorService and it looks up the Add/Subtract/Multiply/Divide services (which are remote over RMI) from the service registry. The CalculatorService is exported as a Web Service.

– The operations bundle registers four remote services (Add/Subtract/Multiply/Divide). These services are exported over RMI.

OSGi Remote Services enabled Calculator

AddService

Operations Bundle

SubtractService

MultiplyService

DivideService

Calculator bundle

CalculatorService RMIWeb Service

RMI

RMI

RMI

OSGi runtime #1OSGi runtime #1 OSGi runtime #2OSGi runtime #2

Modeling OSGi entities using SCA

SCA environment

Add

Service

The Calculator Scenario: OSGi Remote Serviceswith SCA runtime as the distribution software

OSGi bundle

OSGi bundle

SCA Componentimplementation.osgi

SCA Componentimplementation.osgi

Subtract

Service

Multiply

Service

Divide

Service

Calculator

Service

binding.rmi or binding.ws

OperationsCalculator

binding.rmi

binding.ws

OSGI-INF/sca/bundle.composite

Add

Service

Operations Bundle

Subtract

Service

Multiply

Service

Divide

ServiceCalculator bundle

Calculator

Service

SCA bundle

Defining the SCA composite for OSGi bundles

SCA view of OSGi services and references

RMIRMI

RMIRMI

RMIRMI

RMIRMI

Calculator

ServiceWeb

ServiceWeb

Service

SCA proxiesSCA proxies

Local ServiceLocal Service

Local OSGi ServiceImplementation

OSGi Service Registry

Add

Service

Subtract

Service

Multiply

Service

Divide

Service

SCA Service

SCA References

SCA implementation.osgi

• The SCA implementation.osgi component will be used to encapsulate one or more OSGi bundles. – OSGi View: implementation.osgi provides the metadata and

infrastructure to enable the distribution of OSGi services– SCA View: implementation.osgi allows OSGi bundles to

participate in the SCA assembly.

• The references for an SCA OSGi component represents the OSGi services to be consumed by the bundles

• The services for an SCA OSgi component represents the OSGi services to be provided by the bundles

Predefined mapping from OSGi to SCA

http://svn.apache.org/repos/asf/tuscany/java/sca/samples/dosgi-calculator/http://svn.apache.org/repos/asf/tuscany/java/sca/samples/dosgi-calculator-operations/

Mapping an OSGi bundle to an SCA componentType

<componentType xmlns="http://docs.oasis-open.org/ns/opencsa/sca/200903" xmlns:t="http://tuscany.apache.org/xmlns/sca/1.1"> <!-- The service elment defines an SCA view of the OSGi service --> <service name="CalculatorService"> <!-- The interface will be mapped into the OSGi service class --> <interface.java interface="calculator.dosgi.CalculatorService"/></service> <!-- The reference elment defines an SCA proxy to a remote OSGi service --> <reference name="addService"> <interface.java interface="calculator.dosgi.operations.AddService"/> </reference> <reference name="subtractService"> <interface.java interface="calculator.dosgi.operations.SubtractService"/> </reference> <reference name="multiplyService"> <interface.java interface="calculator.dosgi.operations.MultiplyService"/> </reference> <reference name="divideService"> <interface.java interface="calculator.dosgi.operations.DivideService"/> </reference></componentType>

SCA composite for the OSGi bundle

<composite xmlns="http://docs.oasis-open.org/ns/opencsa/sca/200903“ xmlns:tuscany="http://tuscany.apache.org/xmlns/sca/1.1“ targetNamespace=http://calculator.dosgi name="CalculatorComposite"> <component name="CalculatorComponent"> <tuscany:implementation.osgi bundleSymbolicName="calculator.dosgi" bundleVersion="1.0.0" /> <service name="CalculatorService"> <binding.ws uri="http://localhost:8086/CalculatorService"/> </service> <reference name="addService"> <tuscany:binding.rmi uri="rmi://localhost:8085/AddService"/> </reference> <reference name="subtractService"> <tuscany:binding.rmi uri="rmi://localhost:8085/SubtractService"/> </reference> <reference name="multiplyService"> <tuscany:binding.rmi uri="rmi://localhost:8085/MultiplyService"/> </reference> <reference name="divideService"> <tuscany:binding.rmi uri="rmi://localhost:8085/DivideService"/> </reference> </component></composite>

On-demand mapping from OSGi to SCA

http://svn.apache.org/repos/asf/tuscany/java/sca/samples/dosgi-dynamic-calculator/http://svn.apache.org/repos/asf/tuscany/java/sca/samples/dosgi-dynamic-calculator-operations/

Remote Service Admin

NOTE: The diagram is copied from OSGi Remote Service Admin spec (to be published)

Remote Services with SCA

NOTE: The diagram is copied from OSGi Remote Service SCA Configuration Type spec (to be published)

Publish remote services public void start(BundleContext context) throws Exception { Dictionary<String, Object> props = new Hashtable<String, Object>(); props.put("sca.service", "CalculatorComponent#service-

name(Calculator)"); props.put("calculator", "Calculator"); props.put("service.exported.configs", new String[] {"org.osgi.sca"}); props.put("org.osgi.sca.bindings", new String[]

{"{http://sample}Calculator"}); props.put("service.exported.interfaces", new String[] {"*"}); CalculatorService calculator = new CalculatorServiceImpl(context); context.registerService(CalculatorService.class.getName(), calculator,

props);}

Look up remote services (ServiceTracker)

Filter remoteFilter = null;try { remoteFilter = context.createFilter("(&(" + OBJECTCLASS +

"=calculator.dosgi.operations.*) (service.imported=*))");} catch (InvalidSyntaxException e) { …}this.remoteServices = new ServiceTracker(context, remoteFilter, null);remoteServices.open();…Object[] remoteObjects = remoteServices.getServices();

MANIFEST.MFManifest-Version: 1.0Export-Package: calculator.dosgi;version="1.0.1", calculator.dosgi.operations;version="1.0.1"Bundle-Version: 1.0.0Bundle-Name: calculator.dosgi.dynamicBundle-Activator: calculator.dosgi.impl.CalculatorActivatorBundle-ManifestVersion: 2Import-Package: org.oasisopen.sca.annotation;version="2.0.0", org.osgi.framework, org.osgi.service.component;resolution:=optional, org.osgi.service.packageadmin, org.osgi.util.trackerBundle-SymbolicName: calculator.dosgi.dynamicBundle-ActivationPolicy: lazyBundle-RequiredExecutionEnvironment: J2SE-1.5,JavaSE-1.6SCA-Configuration: OSGI-INF/sca-config/calculator-config.xmlRemote-Service: OSGI-INF/remote-service/*.xml

SCA Configuration<scact:sca-config targetNamespace="http://sample" xmlns:scact="http://www.osgi.org/xmlns/scact/v1.0.0" xmlns:sca="http://docs.oasis-open.org/ns/opencsa/sca/200903" xmlns:tuscany="http://tuscany.apache.org/xmlns/sca/1.1"> <sca:binding.ws name="Calculator" uri="http://localhost:8086/CalculatorService"/> <!-- bindings for the remote services --> <tuscany:binding.rmi name="Add" uri="rmi://localhost:8085/AddService"/> <tuscany:binding.rmi name="Divide" uri="rmi://localhost:8085/DivideService"/> <tuscany:binding.rmi name="Subtract" uri="rmi://localhost:8085/SubtractService"/> <tuscany:binding.rmi name="Multiply" uri="rmi://localhost:8085/MultiplyService"/></scact:sca-config>

Local endpoint descriptions<service-descriptions xmlns="http://www.osgi.org/xmlns/sd/v1.0.0" xmlns:sca="http://docs.oasis-open.org/ns/opencsa/sca/200903" xmlns:tuscany="http://tuscany.apache.org/xmlns/sca/1.1"> <!-- Describe a remote OSGi service --> <service-description> <provide interface="calculator.dosgi.operations.AddService" /> <property name="remote.exported.intents"></property> <property name="remote.configs.supported">org.osgi.sca</property> <property name="org.osgi.sca.bindings">{http://sample}Add</property> </service-description>…</service-descriptions>

SCA Domain based service discovery

Domain Registry for OSGi discovery

N ode 1

JVM 1

N ode 2

JVM 2

External clients and services

Domain

Composite 1 Composite 2

c1 c2Contributions definitionsc3

E ndpo in t

E ndpo in t

E ndpo in t

In ten t

P o licy S e t

B ind ing / Im p lem en ta t ion Type

DomainRegistry (Provide a view to the domain metadata)

Nodes receive m etadata (a view) from the S CA dom ain via the reg is try