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Platform Team/Package Management System

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Revision as of 09:41, 26 December 2009 by Walter (talk | contribs) (→‎All sugar developers)


Zero Sugar Distribution

Sugar Services provides transparency for users and convenience for activity developers across varying platforms (and their varying dependencies) as well as across Sugar releases. Sugar Services is a method to support this variety of activity dependencies and variety of dependency versions. In other words, Services is a common deployment system for activity dependencies; it is lightweight like sugargame and like Qt.

Workflows

Sugar Services looks different depending upon your point of view:

Users

In the case of a poor Internet connection (and implemented Zero Install integration feature), users can switch to offline mode and won't encounter any changes in their regular workflow. Switching to online mode brings additional progress bar to the launch dialog for activities that have pending/not-yet-downloaded/out-dated activity dependencies.

Activity developers

Sugar Services makes sense for activities that have non-Sugar Platform dependencies or support more then one Sucrose release cycle.

To utilize the benefits of Services, activity developer need only to mention all services that their activity is using. Services infrastructure will provide specified services (and specified versions) for the activity and will let activity know about them.

Sugar Services let activity developers:

  • use dependencies that are not intended to be included to Sugar Platform
    • including libraries that are used by only a few activities; or
    • have shorter or longer release/support schedules than Sucrose;
  • deploy dependencies that are specific to particular activity; for example, some Python activities include C libraries—by using Services, an activity developer need not bundle these binaries, they could be used as regular activity dependencies.

See Activity Developers Guide to know how to add service dependencies to your activity.

All Sugar developers

Services are intended to decentralize Sugar development process. If you have some idea in mind, you can start pushing it through the Sucrose release queue to get it in the next (maybe not nearest) release. However, since the release process is binary—either your feature is included or not—Services offers more flexibility. For example:

  • some features are of arguable general benefit; Sugar Services would allow interested end users to efficiently test (and even deploy) such features;
  • some feature are only stable in limited environments; Sugar Services would allow deployment in limited environmets without the risk of destabilizing the rest of Sugar.

A developer benefits from 0install features by:

  • letting users of all deployed Sucrose releases benefit from your new feature instead of having it only in a specific (latest) Sucrose release; for example Activity Triggers services;

See Service Developers Guide to know how to create service.

GNU/Linux distributions

The Sugar Platform cannot grow endlessly e.g. installing sugar from packages should not fetch a half of all available packages including several UI toolkits, several programming languages etc., so components like Qt or Ruby are (at least at present) out of Sugar Platform list. But with Sugar Services, activities can still use such dependencies by installing them from native packaging systems by demand and without bundling binaries.

See Native packages usage to know how to utilize native packages in your activity or service.

Detailed description

This proposal assumes that the core of Sugar development (in common sense) is a wide variety of developers, not just those developers who are taking part in Sugar core (glucose) development. It is all about seeing Sugar activity development from an activity/3rd-party developer's point of view.

From such new core POV, sugar development process will look like:

  • variety of Sugar activities
  • that use variety of Sugar Services

So, developers use a set of services that have their own API changes based schedules. Glucose could be wrapped to regular service(s) with proper versioning scheme as well e.g. if glucose's activity API wasn't backwards compatibility broken since 0.82(glucose-0.x service) all activities that requires glucose 0 will be launched but instead of launching activities with requirements glucose 1, user will be warned about outdated sugar environment.

The corner stone of Sugar Services proposal is Saccharin service. This service provides installing/upgrading (via 0install) mechanism for services. The rest of services is just variety of libraries/applications/native-packages. Saccharin could be a part of glucose (some of its releases) or bundled to .xo otherwise.

FAQ

A short list of questions that describe Sugar Services' purposes.

What is Sugar Services not?

  • It is not intended to cure all ills.
  • It is not "must have" for activity developers; use it only if you really need it.
  • Is is not a replacement for GNU/Linux distributions Sugar packaging efforts; Sugar Services places no need for special treatment regarding dependencies as part of the Sugar Platform.
  • It is not intended to be used to support large packages (such as Qt or Firefox) in parallel with distributions. Sugar Services should not be used to avert scenarios such as "It is too bad that you don't have Firefox-3.5 in your three-year-old distribution and cannot run last Browse activity." In such cases, we should require that users update their distribution and Sugar Platform to more recent versions.

How is Sugar Services different?

  • From the point of view of 0install: Sugar Services is just a method to create 0install infrastructure; think about "apt" vs. "dpkg" or "yum" vs. "rpm". In other words, Sugar Services are an analog of 0release command localized to Sugar needs.
  • From the point of view of PackageKit: PackageKit provides a distribution-agnostic method to install already packaged software. Via 0install, Sugar Services let users install unpackaged software as well. More over, 0install will use PackageKit to install missed dependencies if they present in user's distribution.
  • From the point of view of GNU/Linux distributions: see the 0install original goals.

List of services

To see entirely list of services, go to http://download.sugarlabs.org/services/.

Documentation

TODO

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