Dynamic Wiring for implementation.osgi
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Key: TUSCANY-1940
URL: https://issues.apache.org/jira/browse/TUSCANY-1940
Project: Tuscany
Issue Type: New Feature
Components: Java SCA OSGi Integration
Reporter: Rajini Sivaram
This is a placeholder for the work required to support Distributed-OSGi using
SCA metadata and the Tuscany runtime. This is not expected to be committed into
Tuscany until the changes are discussed and finalized on the mailing list.
Graham Charters will be following this up in the new year.
The attached patch supports the following scenarios (based on the BeerOrder
example from RFC 119 for Distributed-OSGi):
<component name="BeerOrderComponent">
<implementation.osgi..../>
<reference name="warehouse" wiredByImpl="true" requires="integrity">
</component>
1) There are two Warehouse Services in the SCA domain. Proxies to both services
are installed by Tuscany in the OSGi registry. One of the services is chosen by
OSGi for BeerOrderComponent/warehouse. At the moment, OSGi properties of the
service are not set on the proxy, but this will be added once the component
description of the service component can be obtained from the SCA domain.
Property matching will be done by OSGi.
2) The warehouse service that the BeerOrderComponent is wired to is removed
from the SCA domain. The proxy corresponding to that warehouse service is
removed from the OSGi registry. OSGi service listener will be used by the
application to rewire to the other warehouse service.
3) The second warehouse service is also removed from the SCA domain. The second
proxy is removed, and the OSGi application's service listener is notified. Any
attempt to use cached proxies will throw an exception.
4) A new warehouse service is added to the SCA domain. A new proxy is installed
in the OSGi registry, and the application's service listener can wire to this
service.
5) Another warehouse service is added to the SCA domain. Another proxy is
installed in the OSGi registry, and the application is notified. But the proxy
to the previously installed service can be used without any disruption.
The changes to the Tuscany runtime to support these scenarios:
1) For references marked wiredByImpl inside a component using
implementation.osgi, the implementation.osgi provider is notified whenever a
matching service becomes available or unavailable. Proxies are
registered/unregistered into the OSGi registry by implementation.osgi.
Matching of interfaces/intents/policies is done by Tuscany, property matching
using OSGi filters is done by OSGi. OSGi applications will be notified when
matching services are available/removed.
2) If a service being used by an OSGi reference becomes unavailable, the OSGi
application will be notified (as long the SCA domain knows about the change).
It is upto the application to wire to a different service. implementation.osgi
registers/unregisters all matching services for references in the service
registry whenever the domain is updated. The rest is handled by OSGi. For OSGi
procedural services, services provided by the bundle will not be affected if
references are not satisfied. For OSGi declarative services, the component will
be deactivated by OSGi if mandatory references are not satisfied.
3) If an additional matching service becomes available, references to other
services should work without exception. And there should be no impact on
services provided by the component. The bundle should not be restarted.
Tuscany will add new wires to the new service, but the wires to previously
installed services will not be modified. This is different from the way
non-OSGi components are handled, where changes to domain cause whole components
to be restarted (causing disruption as well as restarting the scope).
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