Platform Team/Package Management System

Summary

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.

The major difference from existed sugar deployment techniques is that Sugar Services has a point of view of the activity developer. It doesn't exclude (because it reuses them) Sucrose releases or GNU/Linux distribution initiatives, but it does give activity developers an additional (optional) instrument.

Work flows

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.

For such activities, development focus is shifted from Sucrose to an API of services they are using. More over, an activity could be assigned to particular service API version (provided that service developers still support this branch); Sugar Services will support several branches for the same service simultaneously.

To utilize the benefits of Services, activity developer need only to mention all services (or pure 0install feeds) that their activity is using. Services infrastructure will provide specified services (and specified versions) for the activity and will export environment variables, e.g., LD_LIBRARY_PATH or PYTHONPATH, to activity session. Activity developer need not to adapt their code to Services.

Use of non-Sugar Platform dependencies in activities

The Sugar Platform cannot grow endlessly and components like Qt or OO4Kids are (at present) out of Sugar Platform list. But activities can still use such dependencies by installing them from native packaging systems without bundling binaries. See Non Sugar Platform Dependencies Guide to know how to use 0install features.

Service developers

Services could be:

libraries or applications that are not intended to be included to Sucrose
- could be used by few activities
- have shorter or longer release/support schedules
- just a useful way to share your library w/o bundling binary blobs
dependencies that are specific to particular activity e.g. some python activities have C libraries, using Services, activity developer should not bundle all binaries that sugar supports but provide links to binaries that he managed to build and let Services build C libraries from sources on user side in the rest of cases

To create new service, developer needs to create and share proper feed which could be used by activity developers.

Geeks

The entirety of the Sugar Services feature is nothing but a Sugarized UI built around 0install; i.e., feed files that are being used in activity bundles are just regular 0install local feeds. Services could be used to install/upgrade any software (including sugar core components).

Services are not intended for

Cure all ills.
This infrastructure is not "must have", use it only if you really need Services.
Replace GNU/Linux distributions efforts in packaging Sugar, there is no need in special treatment if some dependency is a part of Sugar Platform.
In parallel with distributions, support huge packages like Qt, of course it's still possible but much better to reuse native packages(if they exist) and switch back to "That's really bad that you don't have Firefox-3.5 in your 3 years old distribution, but we can't package Firefox-3.5 for you, so please update your distribution and Sugar Platform to last versions." otherwise.

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 Sugar Services

Developers use a set of services that have their own API changes based schedules. Existed glucose packages will be treated as a big service (split to several components, but thats not a task for this proposal). This proposal is about proposing basic infrastructure of Sugar Services and several services that are not part of glucose.

The corner stone of Sugar Services proposal is Saccharin service. This service provides installing/upgrading (via 0install) mechanism for all other services. The rest of services is just variety of libraries/applications.

Technically, Sugar Services could be a part of glucose (or some of its releases) but from activity POV it doesn't make much sense. If an activity requires some service, Saccharin will do nothing if requested service/version is already a part of the installed glucose or install proper service(via 0install). Various activities on the same system could use various versions of the same service, in that case Saccharin(via 0install) will just provide proper version to particular activity.