gitlab-org/gitlab

Project

The unit of GitLab work — owns a Git repository, issues, MRs, CI configuration, packages, and most user-facing surfaces.

Source

app/models/project.rb (the largest model in the codebase), plus extensions:

ee/app/models/ee/project.rb — EE-only behavior.
Dozens of concerns under app/models/concerns/.
A nested app/models/projects/ namespace for support models.

Key associations

Association	What it owns
`repository`	The Git repo (via Gitaly)
`wiki`	The wiki repo
`merge_requests`, `issues`, `notes`	The issuable graph
`pipelines`, `builds`, `runners`, `runner_projects`	CI
`packages`, `package_files`	Packages
`container_repositories`	Container images
`releases`, `tags`, `protected_branches`	SCM lifecycle
`members`, `project_namespace.namespace_settings`	Access
`integrations`	70+ integrations
`web_hooks`	Outbound hooks
`audit_events`, `audit_events_streaming_destination`	Audit
`vulnerabilities`, `vulnerability_findings`, `merge_request_approvals` (EE)	Security
`labels`, `milestones`, `iterations`	Planning

Visibility

Projects have visibility levels matching their namespace plus optional override:

private — explicit members only.
internal — any logged-in user.
public — everyone.

The Gitlab::VisibilityLevel mixin enforces.

Storage layout

Projects use "hashed storage": the on-disk path is @hashed/<sha>/<sha>.git. The mapping is computed from the project ID. This avoids renames on disk when the project moves between groups.

Lifecycle

State	Triggered by
Created	`Projects::CreateService`
Updated	`Projects::UpdateService`
Transferred	`Projects::TransferService`
Forked	`Projects::ForkService` (creates a fork relation)
Imported	`Projects::ImportService` (and importer pipelines)
Archived	`Projects::UpdateService` setting `archived = true`
Marked for deletion	EE-only delayed deletion
Destroyed	`Projects::DestroyService`

A "fork" relationship lives in fork_network / fork_network_member.

Key services

Service	What it does
`Projects::CreateService`	Provisions repo, default branch, README, CI config option
`Projects::ImportService`	Drives the importer pipeline
`Projects::TransferService`	Moves a project between namespaces
`Projects::DestroyService`	Cleans up repo, packages, CI artifacts, ML metadata, etc.
`Projects::HousekeepingService`	Periodic git gc / pack-objects
`Projects::AfterImportService`	Post-import normalization

Performance hot spots

Project is touched by nearly every request. Common N+1 sources:

Loading project members in nested loops — use BatchLoader and the Member scopes.
Reading wiki/repo size for project-list pages — cache on project_statistics.
Computing a project's effective visibility — use the cached effective_visibility_level.

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