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?

Tooling (builds)

• Enhancements to current export
  • pack/unpack/sign support
  • export to multiple targets (exporting platform dependent fragments)

• Current Export
  • leave behind generated files for debugging purposes

• Project Builder (can we get this into the pde.incubator)
  • a new builder project (like existing update site project)
  • Provides a mechanism to bootstrap from export to headless build
  • generates artifacts (features/build.properties/customTargets.xml/allElements.xml) that are input into pde.build
  • provides forms/editors (or wizards) to expose pde.build options
  • Consider different inputs : .product file, launch configuration
  • enable gradual discovery of customizability: customTargets.xml, plugin level build callbacks.
  • Synchronization between workspace and plugin level build properties.

• PDE/Build proper: selected refactorings to make project builder easier
  • remove need for allElements.xml

Second breakout meeting

API Tooling

• Clarify definition of API (what is API, what is API compatibility)
  • Public API (as defined by Jeem's API white paper)
  • Internal code
  • Provisional API
  • SPI - Service provider interfaces
  • Eclipse-specific API such as extension point ids, other data in extension/extension-point markup
• Tool to annotate code with API rules (javadoc tags that specify if a class may be implemented, instantiated, etc)
• Build API rule file from javadoc tags
• Want both IDE integration, and headless build usage
• Scalability
  • Be able to run API tools on smaller components/bundles/pieces rather than the whole world
  • Store results in various forms: XML files, or perhaps database for large scale use
  • API data may be stored locally or remotely
• Discussion on whether API rule files could replace JDT access restrictions. It's really a super-set of access rules, can express things that acess rules cannot
• API usage reports: could have simple HTML pages, or Eclipse integration into views/editors, like the Emma Eclipse plugin does for coverage data
• Support for API tooling in other languages and .so/DLL files
• Use of reflection is problematic because it's hard to detect programmaticaly

Server Side Remote Management

Provisioning will handle and cover much of the use case around managing the provisioning of servers.

The notion of a "nano" entity for initial provisioning will be useful,

A entity that can be tickled to check, verify and rectify the state of an equinox runtime.

There is not much available for managing totally non-running systems. Systems will need to have something running to talk to.

There are several frameworks to add on top of running osgi systems for managing the installs JMX, MX4J, Remote Console, DMTAdmin.

Things to look into: -DMT Admin: There is no spec available? -OSGi Monitoring Spec.