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.
- 1 Day One Results
- 2 Day Two Results
Day One Results
First breakout meeting
Component Programming Models
- Service helper: ideal for one-time use.
- 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
- 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?
- 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
Server Side Web apps++
Second breakout meeting
- 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
- 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.
Day Two Results
Third breakout meeting
We started with a discussion of requirements for the p2 download manager and transport layer:
- Robustness of download manager
- Different repos have different characteristics - some repos can support many connections
- Adaptive re-prioritization - if you are downloading 1GB of data, you may need to switch to a different mirror dynamically
- Weighting of repositories based on latency, availability, etc.
- For downloading many small pieces, may be more efficient to combine them into a single large artifact for download purposes (minimizing round-trips)
- Not good for many small files
- Great for Eclipse release periods where there are large download peaks.
- Could work well in a corporate environment where a large group of people are provisioning the same software around the same time.
- Where do we embed all this intelligence - in a single uber-smart download manager, or should some of that smarts be hidden away in repository implementations? Could have a single smart repo that acts as a facade to a group of backing repos.
- Scott: ECF is just intended to be a slim asynchronous transfer API - while some of these details could be handled at the transport level, some of this complexity should be built in a layer above ECF
- Requirement for ECF: be able to introspect download stats in order to make adaptive decisions, alter repo weightings, etc.
- Also need new API from ECF to start artifact downloads at a particular offset in an artifact. This is needed both for resume of downloads, and for multi-threaded download of a single file (each thread downloads a chunk, potentially from different mirrors, and then chunks are reassembled upon completion of download)
Getting more concrete on the design and how the pieces fit together. First cut: Intelligence and design making largely in download manager. However, repository implementations need to be able to answer various questions in order for the download manager to be able to make its decisions:
- Memory and disk space requirements
- CPU time requirements
- Latency/throughput of transport
- Download manager also needs to account for local machine characteristics - how many concurrent downloads can it run, etc
Aiming for a relatively simple download manager with pluggable download strategies. Can start with a simple d/l strategy much like our current implementation. Then be able to plug in a much fancier d/l strategy that does mult-threading, adaptive behaviour, etc.
- Modify current d/l manager to have pluggable strategies
- API for asynchronous interaction with repositories
- API for querying progress of repos
- Repo API for starting artifact downloads at some offset in the artifact
"Everything is possible with enough contributions"
self-hosting has been difficult historically
- provision from workspace
- imagine target platform + your workspace are one big repository
- push from workspace
- "Export -> metadata repository"
- ability to batch IU generation
- are we generating a repository as an archive?
- all plugins ar epushed and published in a repository
- archiving of a repository is a build operation
- installing agent and installing and downloading a runnable piece should give the same thing
- when do we integrate the generator during build/exporting?
- long-term we want people to author IUs (editors)
- probably not for 3.4
- for 3.4, we will probably have some sort of feature.xml -> IU translation
- hints, IUs, feature.xml -> generator => IUs
- manage content (browsing, expiration)
- simple APIs for repositories (addIU, removeIU)
- remote generation of metadata and remote management of clients
- what is the "runtime"? is provisioning included in "runtime"?
- how do we manage remote runtimes? DMT admin?
- workspace would be a "management console" using a specific API
- No cost for people doing plain plugin development
- pull model: running instance pulls from workspace implicitly-generated metadata
- Are IUs self-contained?
- we have no support for translation right now
- currently we're replicating common information across IUs
- How do we do translation of IUs?
- tooling support
- Dynamic tooling is a separate topic
- are my bundles really dynamic?
- will removing my bundles remove them completely?
- feature transitioning (branding, icons, etc.)