Equinox Summit 2007 Results

The Equinox Summit 2007 was arranged as a set of lightning talks and a series of breakout sessions. Each session had a number of parallel discussions with self-assigned and self-organizing participants. The groups then reported to a plenary session, summarizing their results and possibly adding more topics to be discussed in further breakouts.

Day One Results

First breakout meeting

Component Programming Models

• Service helper: ideal for one-time use.

• Spring
  • Injection model - no code to acquire the service
  • Client is handed a proxy to the service object
  • Framework manages binding of a real service to the proxy dynamically
  • Distinguish between mandatory and optional service requirements
    • Mandatory: your bundle isn't started until all the mandatory services are available
    • This only guarantees availability at a moment in time: at the moment of startup all mandatory services are available, but they could disappear after that moment.
    • If a mandatory service goes away, the services exported by the bundle needing the service is unregistered.
  • For stateful services, there is a listener model - bind an unbind events occur as service implementations arrive and depart
  • It would be interesting to be able to declare a default service implementation that would be used whenever no real service is available
• Spring and DS require eager activation, but only for service producers. Many bundles are just service consumers, and so they can be lazily started
• Requirements for Spring service support: Spring core, Spring AOP, a few other essential Spring core pieces
• Service Application Toolkit: IBM toolkit for making it easier to work with OSGi services
• How do we reconcile and combine the various component toolkits available: Spring, DS, SAT, extension registry
• Spring initializes the app context asynchronously. Typical Eclipse programming model assumes that all initialization has completed by the time any classes are loaded in that bundle.
• To be scalable, we need a model where service wiring is persisted across sessions, so we don't have the massive event storm of services being started and bound as the system comes up.
• Most bundles are POJO - how do they specify that they need Spring or some other component system to be available at runtime? Ideally 95% of bundles don't know or care about the active component system - but they need some component system to be around at runtime to inject the services they need.
• Can we come up with a common syntax where a bundle can specify its service and extension registry imports/exports, and be agnostic about the runtime that will parse it and provide the runtime capabilities.
• Scoping: extension registry / services are global - how can I publish extensions/services that are only available in a particular scope* only particular set of bundles have access to it. In J2EE world, sometimes only want to register/bind services within a particular web app. Scoped registries - local versus global extension registry.

p2 Design Deep Dive

Interesting topics:

• Profiles/ hierarchy of profiles

• Headless agent; managed installs

• Everything is possible

• Version range lineups,

• Security? JAAS

• Resolver - where does it go? when?

• Plugable download manager

• Plugable communications - within ECF. replacing ECF?