Difference between revisions of "Equinox FrameworkAdmin"

Revision as of 15:57, 24 January 2007

This document is under construction.

Motivation

Generally speaking, an OSGi framework needs some configuration files for its launch. A framework will be launched by invoking java command or by executing an executable launcher file. In the former case, configurations for framework implementation to read will be required. In the latter case, executable launcher file also might read some configuration files at its invocation.

• As in Eclipse, org.eclipse.osgi plug-in that contains main class of equinox framework implementation reads config.ini in a configuration area. In addition, eclipse.exe, an executable launcher, reads eclipse.ini in the same directory of it and invokes a framework implementation.

Currently, the focus of OSGi Service Platform Specification has been to standardize a runtime infrastructure. On the other hand, how to configure and launch a framework is not addressed. Therefore, scenarios such as bootstrapping OSGi on a clean system are left difficult to manage in a framework independent way.

Overview: What does FrameworkAdmin service enable?

We would like to address this problem by proposing FrameworkAdmin service, which allows a bundle running on a framework to do the followings in a framework independent way.

• Set configurations required to launch a framework, such as
  • Java VM location,
  • Java VM arguments,
  • executable launcher location, if used
  • beginning start level and initial bundle start level,
  • Bundles to be installed and started with their start levels,
  • framework configuration location,
  • framework persistent date location,
• Launch a framework with the specified configurations.
• Expect a bundles state if the specified configurations are used for a framework launch.

Terminologies used in here

Framework config files

configuration files that will be read by a framework implementation at its launching, e.g. config.ini in the directory specified by osgi.configuration.area system property as for equinox.

Executable launcher

an executable framework launcher file, e.g. eclipse.exe as for Eclipse.

Launcher config files

configuration files that will be read by an executable launcher, e.g. eclipse.ini as for eclipse.exe.

Bundles state

state of bundles that represents what kinds of bundles are installed, resolved and to be started on a framework.

Scenarios that the API would help

PDE UI

to ease the targeting of various frameworks

Provisioning agent

to setup a non running framework

Building an application

to create all the config files required to run

Running the framework

to configure and start a framework from java command

See [1] [2].

API: Package org.eclipse.equinox.frameworkadmin

Interfaces defined in org.eclipse.equinox.frameworkadmin package will be introduced briefly. See the codes and Java docs in detail.

FrameworkAdmin

The only interface whose implementation will be registered into the OSGi service registry in this package is FrameworkAdmin.

The client bundle will get the appropriate FrameworkAdmin service object that can meet its requirements by filtering service properties in the service registry. An example of filtering is the target framework implementation and its version. As for filtering, later section will explain it in detail. Then, the client will get new instance of Manipulator which plays a main role in this API.

The interface has a method which might return the Manipulator object initialized according to the running framework and launcher state. Detail of this would be introduced later.

In addition, it also has a method to launch a framework according to the specified Manipulator object.

Manipulator

A client bundle can get a Manipulator object by FrameworkAdmin.getManipulator(). This object keeps both a ConfigData object and a LauncherData object, each of which has setter and getter methods on parameters to be required for a framework launch. The client can set some parameters to be required for launching a framework via ConfigData object or LauncherData object. The parameters set in this object can be saved. Where to save is determined according to the parameters set at that time in a way dependent on a target framework and launcher implementation.

The client also can load parameters from framework config files and launcher config files in the specified locations.

After parameters are set to this object either by setting via a ConfigData or a LauncherData or loading from configuration files, FrameworkAdmin.launch(Manipulator, File) will launch a framework according to the current parameters set in this object. It might invoke a framework by java command or executing the specified launcher.

Remember if you have set parameters but not have saved yet, this launch might use other parameters because actual launch will use parameters retrieved from the configuration files.

In addition, Manipulator enables for a client bundle to expect bundles state if the specified configurations are used for launch without actual launch.

ConfigData

ConfigData is a class that keeps some parameters for a Manipulator object such as,

• Bundles list to be installed, with their persistently marked flag as started or not and their start level for its configuration.
• Beginning start level and initial bundle start level.
• System properties dependent on a framework implementation.
• System properties independent of a framework implementation.

For most framework implementations, these parameters will be saved into their framework config files. However, this API doesn't restrict where to save. For example, a framework implementation and a launcher implementation might need to save these parameters not in framework config files but in a launcher config files. It depends on the target implementations.

LauncherData

LauncherData is a class that keeps some parameters for a Manipulator object such as,

• Location of Java VM.
• Java VM arguments.
• Location of framework config files.
• Location of framework persistent data, where a framework implementation saves information to be kept persistently, such as bundles state, permissions of bundles, start level information, private persistent storages for bundles, and so on.
• Clean flag: a flag to clean the specified location of framework persistent data.

For most framework implementations, these parameters will be saved into their launcher config files, if executable launcher is used. However, this API doesn't restrict where to save. As in Apache Felix, location of framework persistent data should be written in its framework config file. Therefore, the implementation of Manipulator for Felix should save it into not launcher config file but its framework config file.

BundlesState

The implementating object of BundlesState will be created by Manipulator object. At the time of its creation, this object will compose bundles state according to the parameters that the Manipulator object keeps. It means, bundles which can be obtained by Manipulator.getConfigData().getBundles() will be installed on a virtually launched framework using parameters about framework persistent data location. If the data location is not empty and clean flag is false, the installed bundles persistently recorded there should be taken into consideration to compose the bundles state.

After creating this object, this object also provides ways for a client to resolve bundles, install additional bundles, uninstall bundles virtually. Modification of this object never affects the parameters of the Manipulator object which created this object.

Provider of these APIs

First of all, we supposed that an implementation of this API for each framework implementation will be provided by the implementators of the target framework, because the persons who know the framework implementation the most are the implementators of the target framework.

For clients to filter the proper service object, the provider must register the FrameworkAdmin object with service properties keyed by the followings.

FrameworkAdmin.SERVICE_PROP_KEY_FW_NAME

String; name of the framework

FrameworkAdmin.SERVICE_PROP_KEY_FW_VERSION

String; version of the framework

FrameworkAdmin.SERVICE_PROP_KEY_LAUNCHER_NAME

String; name of the launcher

FrameworkAdmin.SERVICE_PROP_KEY_LAUNCHER_VERSION

String; version of the launcher

• Current Limitation: there is no version range.Version Range might be required.
• Offline, the implementator of FrameworkAdmin must declare these values and client must know them.

There is another service property name to be standardized.

FrameworkAdmin.SERVICE_PROP_KEY_RUNNING_SYSTEM_FLAG

true if its getRunningManipulator () returns the initialized Manipulator object of running system.

• Detail of it would be introduced later.

Client of these APIs

A client bundle will get appropriate FrameworkAdmin service object from an OSGi service registry by filtering the service properties described previously in order to get the Manipulator objects to handle the desired framework and launcher implementation.

TBD

Which interface should a method of launch operation belong to?

Currently, a method of launch operation belongs to FrameworkAdmin interface. I can separate this API into another interface like "FrameworkLauncher". But I am not sure how much merit of it would be.

• One merit of the separation is, we can restrict some bundles so that can configure a framework but cannot launch it, by not giving ServicePermission("GET","FrameworkLauncher").
• One demerit of it is, number of interface will be increased by one, even if this interface only has one method.

Launching a framework instance in the Same Process

At this point, launching a framework instance in the same process is not considered yet in this API, explicitly. However, it will be supported in the future.

• What is not sure is “general way of launching a framework instance in the same process”. The API might be able to support it (JavaVM and JavaVM arguments are not used for it obviously).

How to handle running framework information?

There is a need for manipulating configurations of not only a non-running framework but also a running framework. While there are several ways to realize it, currently we adopt the following way. The alternatives to realize it are shown Alternatives of Handling a Running Framework.

Current our proposal

The bundle that registers a FrameworkAdmin service for a particular framework and launcher implementation will do at its registration as follows;

1. A bundle checks if the bundle can register a FrameworkAdmin object whose getManipulatorRunning() returns not null but a Manipulator object initialized according to the running framework and launcher implementation, somehow. The way how the bundle checks it is dependent of its target framework and launcher implementation.
2. If no, the bundle registers a FrameworkAdmin service for a target framework and launcher implementation, whose getRunningManipulator() returns null, with specified service properties including the ones representing framework name/version and launcher name/version.
3. If yes, the bundle registers a FrameworkAdmin service for a target framework and launcher implementation, whose getRunningManipulator() returns a Manipulator object initialized according to the running framework and launcher implementation. The registration is done with specified service properties including not only the ones representing framework name/version and launcher name/version, but also FrameworkAdmin.SERVICE_PROP_KEY_RUNNING_SYSTEM_FLAG="true".

Regarding when the bundle should register a FrameworkAdmin service is not addressed. However, the typical timing is at its start up.

A client bundle can get the initialized Manipulator object as follows;

String filter = “(FrameworkAdmin.SERVICE_PROP_KEY_RUNNING_SYSTEM_FLAG=true)”.
ServiceReference references[] = context.getServiceReferences(FrameworkAdmin.class.getName(), filter);
FrameworkAdmin FrameworkAdmin = (FrameworkAdmin) context.getService(references[0]);
Manipulator manipulator = FrameworkAdmin.getManipulatorRunning(); <-- initialized.

Configurator

Bundles provided by this incubator subproject

1. "org.eclipse.equinox.frameworkadmin": API related with FrameworkAdmin and Configurator. In addition, utility classes used for implementing "org.eclipse.equinox.frameworkadmin.equinox", "org.eclipse.equinox.frameworkadmin.knopflerfish", "org.eclipse.equinox.simpleconfigurator" and "org.eclipse.equinox.simpleconfigurator.manipulator
2. "org.eclipse.equinox.frameworkadmin.equinox": Implementation of FrameworkAdmin service for Equinox. See javadoc of BundleActivator of this plug-in.
   • It supports taking framework persistent data into consideration and supports resolving bundles, if running on the Equinox.
   • It supports taking a configurator bundle into consideration.
   • Limitation of current implementation:
     • A bundle must be JAR.
     • FrameworkAdmin.getRunningManipulator() returns not null just if the vendor and bundle version of running system bundle equal the target. The launcher name and version is not checked.
       • For checking the launcher name and version, eclipse.exe needs to tell them to a fw launching.
3. "org.eclipse.equinox.frameworkadmin.felix": Implementation of FrameworkAdmin service for Apache Felix. See javadoc of BundleActivator of this plug-in.
   • Essentially, this bundle should be provided by the implementator of Felix. This implementation is tentative.
   • No supports for taking framework persistent data into consideration nor supports resolving bundles.
   • It supports taking a configurator bundle into consideration.
4. "org.eclipse.equinox.frameworkadmin.knopflerfish": Implementation of FrameworkAdmin service for Knopflerfish. See javadoc of BundleActivator of this plug-in.
   • Essentially, this bundle should be provided by the implementator of Knopflerfish. This implementation is tentative.
   • No supports for taking framework persistent data into consideration nor supports resolving bundles.
   • It supports taking a configurator bundle into consideration.
5. "org.eclipse.equinox.simpleconfigurator": Implementation of SimpleConfigurator.
6. "org.eclipse.equinox.simpleconfigurator.manipulator": Implementation of ConfiguratorManipulator for SimpleConfigurator.
7. "org.eclipse.equinox.frameworkadmin.examples": An example of client bundle of the APIs related with FrameworkAdminr.

To understand how a provider implements the APIs, see bundle 1 and 2. To understand how a client uses the API, see bundle 1 and 8.

References

1. Requirements for a new update manager (of Eclipse)
2. Requirements discussed in OSGi Alliance Enterprise Workshop
3. Equinox: Runtime options of Eclipse 3.2
4. Felix: Usage
5. Knopflerfish: Usage