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org.osgi.service.remoteserviceadmin

Details of Remote Services and Remote Service Administration specification can be found in Release 4 Version 4.2 of OSGi Service Platform Enterprise Specification

These specifications together provide the discovery and service re-moting foundations necessary for building adaptive distributed OSGi based service oriented systems. The architecture defined by these specifications allowing (implementation dependent):

  • Remote Service to come and go; so addressing 1 & 5 of Peter Deutsch Fallacies; see The Eight Fallacies of Distributed Computing
  • A framework to support multiple distribution providers
  • A framework to support multiple discovery providers
  • The ability to dynamically added and remove providers from a running environment.

Local Services

As a reminder, OSGi services within a single JVM are represented as follows:

![centre Local Services](RSA-3.png “centre Local Services”)

Remote Services

In remote services, a distribution provider detects services in the local JVM (framework1) and publishes them to network endpoints. On the consumer side (framework 2), the distribution provider detects the network endpoints and creates proxy services for them. The consumer sees an ordinary service, and need not be aware that the actual service implementation is remote.

![centre Remote Services](RSA-4.png “centre Remote Services”)

Anatomy of a RSA Provider

  1. Service E has a service property service.exported.interfaces set.
  2. Local Topology Manager is informed of Service E.
  3. Based on policy, the Topology Manager informs registered Remote Service Admin services.
  4. If a Remote Service Admin can support Service E it creates a Service E endpoint.
  5. The framework wires the service endpoint to service.
  6. The Remote Service Admin also creates an Endpoint Description and passes this to registered Discovery Providers.
  7. Each Discovery Provider encapsulates the Endpoint Description in the appropriate manner and issues an implementation specific advertisement.

NOTE: multiple concurrent discovery providers can be supported.


![ centre Provider](RSA-1.png “ centre Provider”)

Anatomy of an RSA Consumer

  1. Discovery Provider X receives a remote-advertisement fromService E.
  2. Service E’s endpoint description is unpacked and sent to the local Topology Manager.
  3. The Topology Manager is aware that Service B has a reference to Service E, hence the Topology Manager sends the Endpoint Description to the appropriate Remote Service Admin.
  4. The Remote Service Admin creates a local proxy for Service E.
  5. The framework wires Service E proxy to Service B.
![ centre Consumer](RSA-2.png “ centre Consumer”)

Implementations

For a list of available Remote Services Admin implementations, see https://en.wikipedia.org/wiki/OSGi_Specification_Implementations

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