OSGi Remote Services with SCA using Apache Tuscany

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OSGi Remote Services with SCA using Apache Tuscany

• Raymond Feng
• rfeng_at_apache.org

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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
• QA

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What are OSGi remote services?
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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?

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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)

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OSGi Remote Services
NOTE The diagram is copied from OSGi Service
Platform Service Compendium R4.2 spec
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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-e
  arly-draft4.pdf

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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.

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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.

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OSGi remote services- A sample scenario
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An OSGi based Calculator
Add Service
Subtract Service
Calculator Service
Multiply Service
Divide Service
Calculator bundle
Operations Bundle
Calculator Service
OSGi service
OSGi service interface
OSGi service reference
OSGi service implementation
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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.

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OSGi Remote Services enabled Calculator
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Modeling OSGi entities using SCA
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The Calculator Scenario OSGi Remote
Services with SCA runtime as the distribution
software
SCA Component implementation.osgi
binding.rmi or binding.ws
SCA Component implementation.osgi
Add Service
Subtract Service
Multiply Service
Calculator Service
Divide Service
OSGi bundle
OSGi bundle
SCA environment
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Defining the SCA composite for OSGi bundles
OSGI-INF/sca/bundle.composite
SCA bundle
binding.rmi
binding.ws
Operations
Calculator
Add Service
Subtract Service
Calculator Service
Multiply Service
Divide Service
Calculator bundle
Operations Bundle
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SCA view of OSGi services and references
Local Service
OSGi Service Registry
Local OSGi Service Implementation
SCA Service
Calculator Service
Web Service
Add Service
RMI
Subtract Service
RMI
Multiply Service
RMI
RMI
Divide Service
SCA References
SCA proxies
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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

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Predefined mapping from OSGi to
SCAhttp//svn.apache.org/repos/asf/tuscany/java/
sca/samples/dosgi-calculator/http//svn.apache.or
g/repos/asf/tuscany/java/sca/samples/dosgi-calcula
tor-operations/
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Mapping an OSGi bundle to an SCA componentType

• ltcomponentType xmlns"http//docs.oasis-open.org/n
  s/opencsa/sca/200903"
• xmlnst"http//tuscany.apache.org/xmlns/sca/1.1"
  gt
• lt!-- The service elment defines an SCA view
  of the OSGi service --gt
• ltservice name"CalculatorService"gt
• lt!-- The interface will be mapped into
  the OSGi service class --gt
• ltinterface.java interface"calculator.dosg
  i.CalculatorService"/gt
• lt/servicegt
• lt!-- The reference elment defines an SCA
  proxy to a remote OSGi service --gt
• ltreference name"addService"gt
• ltinterface.java interface"calculator.dosg
  i.operations.AddService"/gt
• lt/referencegt
• ltreference name"subtractService"gt
• ltinterface.java interface"calculator.dosg
  i.operations.SubtractService"/gt
• lt/referencegt
• ltreference name"multiplyService"gt
• ltinterface.java interface"calculator.dosg
  i.operations.MultiplyService"/gt
• lt/referencegt
• ltreference name"divideService"gt
• ltinterface.java interface"calculator.dosg
  i.operations.DivideService"/gt

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SCA composite for the OSGi bundle

• ltcomposite xmlns"http//docs.oasis-open.org/ns/op
  encsa/sca/200903
• xmlnstuscany"http//tuscany.apache.org/xmlns
  /sca/1.1
• targetNamespacehttp//calculator.dosgi
  name"CalculatorComposite"gt
• ltcomponent name"CalculatorComponent"gt
• lttuscanyimplementation.osgi
  bundleSymbolicName"calculator.dosgi"
  bundleVersion"1.0.0" /gt
• ltservice name"CalculatorService"gt
• ltbinding.ws uri"http//localhost8086
  /CalculatorService"/gt
• lt/servicegt
• ltreference name"addService"gt
• lttuscanybinding.rmi
  uri"rmi//localhost8085/AddService"/gt
• lt/referencegt
• ltreference name"subtractService"gt
• lttuscanybinding.rmi
  uri"rmi//localhost8085/SubtractService"/gt
• lt/referencegt
• ltreference name"multiplyService"gt
• lttuscanybinding.rmi
  uri"rmi//localhost8085/MultiplyService"/gt
• lt/referencegt
• ltreference name"divideService"gt
• lttuscanybinding.rmi
  uri"rmi//localhost8085/DivideService"/gt

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On-demand mapping from OSGi to SCAhttp//svn.apa
che.org/repos/asf/tuscany/java/sca/samples/dosgi-d
ynamic-calculator/http//svn.apache.org/repos/asf
/tuscany/java/sca/samples/dosgi-dynamic-calculator
-operations/
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Remote Service Admin
NOTE The diagram is copied from OSGi Remote
Service Admin spec (to be published)
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Remote Services with SCA
NOTE The diagram is copied from OSGi Remote
Service SCA Configuration Type spec (to be
published)
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Publish remote services

• public void start(BundleContext context) throws
  Exception
• DictionaryltString, Objectgt props new
  HashtableltString, Objectgt()
• props.put("sca.service",
  "CalculatorComponentservice-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//sampleCalculator")
• props.put("service.exported.interfaces",
  new String "")
• CalculatorService calculator new
  CalculatorServiceImpl(context)
• context.registerService(CalculatorService.
  class.getName(), calculator, props)

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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.getService
  s()

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MANIFEST.MF

• Manifest-Version 1.0
• Export-Package calculator.dosgiversion"1.0.1",
• calculator.dosgi.operationsversion"1.0.1"
• Bundle-Version 1.0.0
• Bundle-Name calculator.dosgi.dynamic
• Bundle-Activator calculator.dosgi.impl.Calculator
  Activator
• Bundle-ManifestVersion 2
• Import-Package org.oasisopen.sca.annotationversi
  on"2.0.0",
• org.osgi.framework,
• org.osgi.service.componentresolutionoptional,
• org.osgi.service.packageadmin,
• org.osgi.util.tracker
• Bundle-SymbolicName calculator.dosgi.dynamic
• Bundle-ActivationPolicy lazy
• Bundle-RequiredExecutionEnvironment
  J2SE-1.5,JavaSE-1.6
• SCA-Configuration OSGI-INF/sca-config/calculator-
  config.xml
• Remote-Service OSGI-INF/remote-service/.xml

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SCA Configuration

• ltscactsca-config targetNamespace"http//sample"
• xmlnsscact"http//www.osgi.org/xmlns/scact/v
  1.0.0"
• xmlnssca"http//docs.oasis-open.org/ns/openc
  sa/sca/200903"
• xmlnstuscany"http//tuscany.apache.org/xmlns
  /sca/1.1"gt
• ltscabinding.ws name"Calculator"
  uri"http//localhost8086/CalculatorService"/gt
• lt!-- bindings for the remote services --gt
• lttuscanybinding.rmi name"Add"
  uri"rmi//localhost8085/AddService"/gt
• lttuscanybinding.rmi name"Divide"
  uri"rmi//localhost8085/DivideService"/gt
• lttuscanybinding.rmi name"Subtract"
  uri"rmi//localhost8085/SubtractService"/gt
• lttuscanybinding.rmi name"Multiply"
  uri"rmi//localhost8085/MultiplyService"/gt
• lt/scactsca-configgt

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Local endpoint descriptions

• ltservice-descriptions xmlns"http//www.osgi.org/x
  mlns/sd/v1.0.0"
• xmlnssca"http//docs.oasis-open.org/ns/openc
  sa/sca/200903"
• xmlnstuscany"http//tuscany.apache.org/xmlns
  /sca/1.1"gt
• lt!-- Describe a remote OSGi service --gt
• ltservice-descriptiongt
• ltprovide interface"calculator.dosgi.opera
  tions.AddService" /gt
• ltproperty name"remote.exported.intents"gtlt
  /propertygt
• ltproperty name"remote.configs.supported"gt
  org.osgi.scalt/propertygt
• ltproperty name"org.osgi.sca.bindings"gtht
  tp//sampleAddlt/propertygt
• lt/service-descriptiongt
• lt/service-descriptionsgt

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SCA Domain based service discovery
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Domain Registry for OSGi discovery