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OSGi goes beyond service invocations in a single JVM with the introduction of RFC 119 - Distributed OSGi. It will enable an OSGi bundle deployed in a JVM to invoke a service (either OSGi or non-OSGi) in another JVM or process, potentially on a remote computer accessed via a network protocol. Meanwhile, an OSGi service deployed in another JVM or a non-OSGi program such as Web Service client, potentially on a remote computer, to find and access a service running in the "local" OSGi JVM (i.e. an OSGi deployment can accept service invocations from remote OSGi bundle or external environments). The distributed computing functionality is added to the OSGi programming model without additional APIs or concepts as the distribution layer will be mostly transparent to OSGi developers by configuration.SCA (Service Component Architecture) provides a technology-neutral approach to abstract business logic into components and assemble them into composite applications. It greatly simplifies the component communications using declarative bindings. QoS requirements can be uniformly declared as SCA intents which can be mapped and realized using different stacks. SCA is a great fit to be a distribution provider for distributed OSGi.Apache Tuscany is an open source project that implements the SCA specifications. It provides integrations of implementation types (such as Java, Scripting, BPEL, Spring, OSGi and JEE) and binding types (such as Web Service, JMS, EJB, CORBA, RMI, JSONRPC, and ATOM) as the infrastructure for SCA programming. The latest version of Tuscany runtime is fully built on top of OSGi as the foundation. We recently added the OSGi RFC 119 support.In this session, we will teach you how to develop a distributed OSGi application to leverage the SCA capabilities using Apache Tuscany. A calculator scenario will be used to demonstrate the distributed OSGi service invocations using RMI and Web Service protocols. We will also explain how to model an OSGi bundle as an SCA component and configure the SCA composite to provide communications between services. The readers will understand the basic ideas behind distributed OSGi in the concrete example and the power of Tuscany SCA for service composition.
Citation preview
OSGi Remote Services with SCA using Apache Tuscany
Raymond Feng
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
Local/Domain Registry for OSGi discovery
Calculator
Service
SCA proxiesSCA proxies
Local ServiceLocal Service
Local OSGi ServiceImplementation
OSGi Service Registry
Subtract
Service
Multiply
Service
Divide
Service
OSGi Service Registry
Add
Service
Subtract
Service
Multiply
Service
Divide
Service
RMIRMI
RMIRMI
Add
Service
OSGi runtime #1OSGi runtime #1 OSGi runtime #2OSGi runtime #2
Node
Node
ListenerHook
Filter Matching
ServiceTracker
SCA Domain
Endpoint descriptionsin Local XML file
Endpoint descriptionsin Local XML file
SCA Domain Registry•Endpoints•Intent/PolicySet Definitions
SCA Domain Registry•Endpoints•Intent/PolicySet Definitions
