RFC- uyuni support snap

accepted/00000-snap-package-support.md

@@ -0,0 +1,175 @@
+- Feature Name: support snap in ubuntu 22.04
+- Start Date: 6/01/2025
+
+# Summary
+[summary]: #summary
+
+Introduce Snap support in Uyuni, allowing users to:
+
+Install, update, and remove Snap packages.
+
+Manage Snap channels (stable, candidate, beta, edge).
+
+Handle Snap package management in airgapped environments.
+
+# Motivation
+[motivation]: #motivation
+
+Since Ubuntu 22.04 LTS, the Snap package technology has gained significant traction, and with the Ubuntu 24.04 LTS release, many deb packages are being migrated to Snap.
+
+With this increasing adoption of Snap packages in Ubuntu, Uyuni lacks native support for managing Snap-based applications. This creates a gap in package management, especially as more software is distributed via Snap.
+
+
+# Detailed design
+[design]: #detailed-design
+
+1 Data Analsis 
+
+Total unique packages: 6564 (6/11/2025)
+Total stable packages: 6564
+Architecture count in stable packages:
+  - amd64: 6463
+  - armhf: 45
+  - arm64: 58
+  - all: 101
+  - i386: 67
+  - ppc64el: 10
+  - s390x: 10
+
+Total unique packages checked: 13746
+- Total in 'beta': 1677
+- Total in 'candidate': 1782
+- Total in 'edge': 3740
+
+Total size: 493 GB  around 500GB
+Average package size: 76.82 MB
+
+At this stage, we may be able to store the beta and candidate Snap packages in the cache.
+However, since .snap binary packages are typically two to three times larger than .deb packages, it may be more efficient to use a pre-selection strategy for the stable channel.
+
+Proposed approach:
+
+1. Load the full list of available packages.
+
+2. Allow the client to select which packages they want to manage.
+
+3. Download only the selected packages to the repository cache. (by this way support part of airgap environment)
+
+2 Snap Repository Synchronization Workflow
+
+```text
+┌────────────────────────────────────────────┐
+│          spacewalk-repo-sync CLI           │
+│  $ spacewalk-repo-sync --channel=          │
+│    ubuntu_22.04_snap_stable --type=snap    │
+└────────────┬───────────────────────────────┘
+             │
+             │ Note: Snap packages do not have a public URL,
+             │       so no URL is required in CLI.
+             ▼
+┌────────────────────────────────────────────┐
+│            reposync.py (main logic)        │
+│ - Selects plugin by repo_type              │
+└────────────┬───────────────────────────────┘
+             │
+             ▼
+┌────────────────────────────────────────────┐
+│          snap_src.py (Snap plugin)         │
+│ - Creates ContentSource                    │
+│ - Wraps SnapRepo                           │
+└────────────┬───────────────────────────────┘
+             │
+             ▼
+┌────────────────────────────────────────────────────────────┐
+│        SnapRepo.get_all_package_list()                     │
+│  - Calls: https://api.snapcraft.io/api/v1/snaps/search?q={query}&limit={limit}    │
+│  - Creates SnapPackage objects (name, path, etc.)          │
+└────────────┬───────────────────────────────────────────────┘
+             │
+             ▼
+┌────────────────────────────────────────────────────────────┐
+│        SnapRepo.get_select_package_list()                  │
+│  - Filters selected packages                               │
+│  - Creates SnapPackage objects (name, path, etc.)          │
+└────────────┬───────────────────────────────────────────────┘
+             │
+             ▼
+┌────────────────────────────────────────────────────────────┐
+│            SnapRepo._download(url)                         │
+│  - Performs HTTP download of selected .snap file           │
+│  - GET https://api.snapcraft.io/v2/snaps/info/<snap_name> │
+└────────────┬───────────────────────────────────────────────┘
+             │
+             ▼
+┌────────────────────────────────────────────────────────────┐
+│      reposync.py → import_packages()                       │
+│  - Imports metadata into the database                      │
+│  - Saves .snap files under /var/spacewalk/packages/        │
+└────────────┬───────────────────────────────────────────────┘
+             │
+             ▼
+┌────────────────────────────────────────────────────────────┐
+│   Minions can now use Uyuni as a Snap repository           │
+│   (served through Uyuni-hosted channels)                   │
+│   e.g. `sudo snap install <pkg>` from Uyuni server         │
+└────────────────────────────────────────────────────────────┘
+```
+
+Fake URL Design for Snap Repositories
+
+Snap packages are distributed via the Snap Store using dynamic APIs rather than static URLs. To maintain consistency with other repository types (e.g., YUM, DEB),  introduce a Fake URL format to represent Snap sources uniformly in the database.
+
+Fake URL Format:
+```
+snap://<repo label>/<stable/edge/candidate/beta>
+```
+
+
+These URLs are not used for actual downloads. Instead, they serve as unique identifiers stored in the rhnContentSource.source_url field. The real package fetching will be handled through the Snap API.
+
+This approach keeps the database structure consistent, simplifies repository logic, and supports multiple Snap channels (managed through the rhnSnapChannel table).
+
+When a client creates a Snap repository through the UI, they do not need to enter a URL—only the channel (stable, edge, candidate, or beta) and a repository label are required. The API will automatically generate a fake URL internally.
+
+However, when creating a Snap repository using spacemd, the user may manually specify a fake URL, for example:
+```
+repo_create --name="Snap Store Repo" --url="https://fake.url" --type=snap
+```
+
+
+3 DB DESIGN
+
+rhnChannel stores basic channel information, such as label, org_id
+rhnContentSource stores the actual repo URL
+rhnChannelContentSource channel and content source mapping table (channel ↔ repo)
+
+Uyuni’s current database schema (rhnContentSource, rhnContentSourceType, rhnChannel) is designed for repositories like YUM or DEB, which use a static URL and do not have multi-channel semantics.
+
+However, Snap packages are distributed via multiple dynamic channels (e.g., stable, beta, candidate, edge) under a track (e.g., latest). The existing schema does not provide a way to associate a Snap repository with multiple channels, nor a place to store their metadata.
+``` text
+CREATE TABLE rhnSnapChannel (
+    id SERIAL PRIMARY KEY,
+    content_source_id INTEGER REFERENCES rhnContentSource(id) ON DELETE CASCADE,
+    channel VARCHAR(64) NOT NULL,
+    created TIMESTAMP WITH TIME ZONE DEFAULT now(),
+    modified TIMESTAMP WITH TIME ZONE DEFAULT now()
+);
+
+-- Insert 'snap' repo type
+insert into rhnContentSourceType (id, label) values
+(sequence_nextval('rhn_content_source_type_id_seq'), 'snap');
+
+-- Register supported channels for the repo
+INSERT INTO rhnSnapChannel (content_source_id, channel) VALUES
+(600, 'stable'),
+(600,  'beta'),
+(600, 'candidate'),
+(600,  'edge');
+```
+
+
+
+4 UI design 
+
+To be continue
+