Difference between revisions of "Equinox/p2/Engine/Galileo"

Revision as of 00:04, 16 October 2008

Note: current activity is being prototyped in the "engine_changes_3_5" branch for:

* org.eclipse.equinox.p2.engine
* org.eclipse.equinox.p2.metadata
* org.eclipse.equinox.p2.metadata.repository
* org.eclipse.equinox.p2.tests
* org.eclipse.equinox.p2.touchpoint.eclipse
* org.eclipse.equinox.p2.touchpoint.native

Greater flexibility around touchpoints and actions

Currently an IU references a single touchpoint and then may only use actions from that touchpoint while performing the provisioning operation in the Engine. As a result of this restriction we've ended up with duplicate actions (e.g. chmod, mkdir, rmdir) in both the "eclipse" and "native" touchpoints. In addition, any user wanting to do anything outside of what's scoped by our current actions is forced to write their own touchpoint and collection of actions.

There is a bug open covering this requirement here -- https://bugs.eclipse.org/bugs/show_bug.cgi?id=203323

Approaches under consideration:

• Add an "actions" extension point (touchpint reference and IU authoring metadata). This changes the action/touchpoint relationship so that an action now refers to a touchpoint instead of the other way around.

-name
-version
-class
-touchpointType
-touchpointVersion

• Adjust the Engine's action lookup to use actions extensions. This might force us to adjust some of the lifecycle events for touchpoints as they should only be involved in phases where there are associated actions.
• When referencing an action in the metadata we want to add an "actions" attribute to help disambiguate actions with the same name from different providers. As a result the Touchpoint Data instructions will likely have to be updated to include information to disambiguate actions.

<instruction key='configure' 
 qualifier='org.eclipse.equinox.p2.touchpoint.eclipse.setStartLevel;version=[1.0,2.0),
  org.eclipse.equinox.p2.touchpoint.eclipse.markStarted;version=[1.0,2.0)'>
 setStartLevel(startLevel:2);markStarted(started: true);
</instruction>

• To try to be backwards compatible with existing action metadata, upon encountering an unqualified action name the actionlookup algorithm will give the IU's touchpoint a chance to qualify the action name. For example the eclipse touchpoint might qualify the action name "installBundle" into the qualified name "org.eclipse.equinox.p2.touchpoint.eclipse.installBundle".

Some questions we're not sure about:

• What if anything do we want to do about substitutability of actions?

Authoring and validation metadata in touchpoints, actions and phases

We have a general lack of validation mechanisms that provide the user the oppportunity to apply corrective action. For example, there is no way to indicate the need for user interaction when required configuration properties are missing. In addition there is a shortage of useful metadata to allow one to construct a useful IU authoring environment without having to know the inner details of phases, touchpoints, and actions.

Approaches under consideration:

• Add "description" elements to the touchpoint and action extensions to allow one to add a localizable description of the item.
• Consider adding a "phases" extension just to hold metadata useful for authoring and validation
• Add some paramater validation metadata. For example a touchpoint might want to add some metadata to describe it's profile properties requirements. The user might then get a specially purposed UI to add those properties.

-profileProperties
 -name
 -description (localizable)
 -type (string, number, boolean)
 -use (optional, required)
 -default (implies optional)

• One good source we already have for some of this metadata is Equinox/p2/Engine/Touchpoint Instructions.
• Add new validation phases similar to sizing for unconfigure, uninstall, property, install, configure. This will allow us to create a validation phase set the ui or other clients can run to determine if there are elements used by the engine that need to be first installed or configured.

Install Handler like mechanism

We currently lack a general mechanism to allow a user to use actions that are not currently installed/avialable in the agent while in the process of an install. This is particularly important since Update Manager had Install Handlers for this usecase.

Approaches under consideration:

• Provide is a special "dynamicAction" that allow one to reference an artifact in the IU and then load a special class from a jar file and run it. This is similar to what we had with InstallHandlers and as a consequence will have the same limitations around authoring and build.
• Sort out a way to let us install the necessary bundles that contain the actions and touchpoints we need to proceed in an install. This might be a workflow we drive through the UI or just do behind the scenes in a nested transaction.