debian-mirror-gitlab/doc/development/packages.md

Packages (PREMIUM)

This document will guide you through adding another package management system support to GitLab.

See already supported package types in Packages documentation

Since GitLab packages' UI is pretty generic, it is possible to add basic new package system support with solely backend changes. This guide is superficial and does not cover the way the code should be written. However, you can find a good example by looking at merge requests with Maven and NPM support:

• NPM registry support.
• Conan repository.
• Maven repository.
• Instance level endpoint for Maven repository

General information

The existing database model requires the following:

• Every package belongs to a project.
• Every package file belongs to a package.
• A package can have one or more package files.
• The package model is based on storing information about the package and its version.

API endpoints

Package systems work with GitLab via API. For example ee/lib/api/npm_packages.rb implements API endpoints to work with NPM clients. So, the first thing to do is to add a new ee/lib/api/your_name_packages.rb file with API endpoints that are necessary to make the package system client to work. Usually that means having endpoints like:

• GET package information.
• GET package file content.
• PUT upload package.

Since the packages belong to a project, it's expected to have project-level endpoint (remote) for uploading and downloading them. For example:

GET https://gitlab.com/api/v4/projects/<your_project_id>/packages/npm/
PUT https://gitlab.com/api/v4/projects/<your_project_id>/packages/npm/

Group-level and instance-level endpoints are good to have but are optional.

Remote hierarchy

Packages are scoped within various levels of access, which is generally configured by setting your remote. A remote endpoint may be set at the project level, meaning when installing packages, only packages belonging to that project will be visible. Alternatively, a group-level endpoint may be used to allow visibility to all packages within a given group. Lastly, an instance-level endpoint can be used to allow visibility to all packages within an entire GitLab instance.

Using group and project level endpoints will allow for more flexibility in package naming, however, more remotes will have to be managed. Using instance level endpoints requires stricter naming conventions.

The current state of existing package registries availability is:

Repository Type	Project Level	Group Level	Instance Level
Maven	Yes	Yes	Yes
Conan	No - open issue	No - open issue	Yes
NPM	No - open issue	Yes	No - open issue

NOTE: Note: NPM is currently a hybrid of the instance level and group level. It is using the top-level group or namespace as the defining portion of the name (for example, @my-group-name/my-package-name).

Naming conventions

To avoid name conflict for instance-level endpoints you will need to define a package naming convention that gives a way to identify the project that the package belongs to. This generally involves using the project id or full project path in the package name. See Conan's naming convention as an example.

For group and project-level endpoints, naming can be less constrained, and it will be up to the group and project members to be certain that there is no conflict between two package names, however the system should prevent a user from reusing an existing name within a given scope.

Otherwise, naming should follow the package manager's naming conventions and include a validation in the package.md model for that package type.

File uploads

File uploads should be handled by GitLab Workhorse using object accelerated uploads. What this means is that the workhorse proxy that checks all incoming requests to GitLab will intercept the upload request, upload the file, and forward a request to the main GitLab codebase only containing the metadata and file location rather than the file itself. An overview of this process can be found in the development documentation.

In terms of code, this means a route will need to be added to the GitLab Workhorse project for each level of remote being added (instance, group, project). This merge request demonstrates adding an instance-level endpoint for Conan to workhorse. You can also see the Maven project level endpoint implemented in the same file.

Once the route has been added, you will need to add an additional /authorize version of the upload endpoint to your API file. Here is an example of the additional endpoint added for Maven. The /authorize endpoint verifies and authorizes the request from workhorse, then the normal upload endpoint is implemented below, consuming the metadata that workhorse provides in order to create the package record. Workhorse provides a variety of file metadata such as type, size, and different checksum formats.

For testing purposes, you may want to enable object storage in your local development environment.

Services and finders

Logic for performing tasks such as creating package or package file records or finding packages should not live within the API file, but should live in services and finders. Existing services and finders should be used or extended when possible to keep the common package logic grouped as much as possible.

Configuration

GitLab has a packages section in its configuration file (gitlab.rb). It applies to all package systems supported by GitLab. Usually you don't need to add anything there.

Packages can be configured to use object storage, therefore your code must support it.

Database and handling metadata

The current database model allows you to store a name and a version for each package. Every time you upload a new package, you can either create a new record of Package or add files to existing record. PackageFile should be able to store all file-related information like the file name, side, sha1, etc.

If there is specific data necessary to be stored for only one package system support, consider creating a separate metadata model. See packages_maven_metadata table and Packages::MavenMetadatum model as an example for package specific data, and packages_conan_file_metadata table and Packages::ConanFileMetadatum model as an example for package file specific data.

If there is package specific behavior for a given package manager, add those methods to the metadata models and delegate from the package model.

Note that the existing package UI only displays information within the packages_packages and packages_package_files tables. If the data stored in the metadata tables need to be displayed, a ~frontend change will be required.

Authorization

There are project and group level permissions for read_package, create_package, and destroy_package. Each endpoint should authorize the requesting user against the project or group before continuing.

Keep iterations small

When implementing a new package manager, it is easy to end up creating one large merge request containing all of the necessary endpoints and services necessary to support basic usage. If this is the case, consider putting the API endpoints behind a feature flag and submitting each endpoint or behavior (download, upload, etc) in different merge requests to shorten the review process.

Potential MRs for any given package system

MVC MRs

These changes represent all that is needed to deliver a minimally usable package management system.

1. Empty file structure (API file, base service for this package)
2. Authentication system for 'logging in' to the package manager
3. Identify metadata and create applicable tables
4. Workhorse route for object storage direct upload
5. Endpoints required for upload/publish
6. Endpoints required for install/download
7. Endpoints required for remove/delete

Possible post-MVC MRs

These updates are not essential to be able to publish and consume packages, but may be desired as the system is released for general use.

1. Endpoints required for search
2. Front end updates to display additional package information and metadata
3. Limits on file sizes
4. Tracking for metrics

Exceptions

This documentation is just guidelines on how to implement a package manager to match the existing structure and logic already present within GitLab. While the structure is intended to be extendable and flexible enough to allow for any given package manager, if there is good reason to stray due to the constraints or needs of a given package manager, then it should be raised and discussed within the implementation issue or merge request to work towards the most efficient outcome.