GitLab

GitLab is an open-core, single-application DevSecOps platform that combines Git repository hosting, code review, CI/CD, container and package registries, security scanning, observability, and project management in one Ruby on Rails monolith. The canonical source lives at gitlab-org/gitlab on GitLab.com, and the same code powers both self-managed installations and the GitLab.com SaaS service. Most of the tree is MIT-licensed; files under ee/ are proprietary but source-available.

This wiki documents the canonical monorepo at version 19.0.0-pre (default branch: master). It is intended for engineers contributing to GitLab itself, not end users administering an installation. For user-facing documentation, see https://docs.gitlab.com.

What's in the box

The repository contains:

• A Rails 7.2 web application (app/, lib/, config/) that serves the web UI, REST API, and GraphQL API.
• A Vue.js / TypeScript frontend in app/assets/javascripts/ plus standalone "frontend islands" in frontend_islands/ and ee/frontend_islands/.
• The Enterprise Edition tree under ee/ (proprietary features: Geo, advanced security, Duo, audit events, etc.).
• Workhorse — a Go reverse proxy that handles long-running and resource-intensive HTTP traffic in front of Puma.
• The Sidekiq cluster for background jobs, with ~170 worker namespaces.
• A QA/end-to-end test framework in qa/.
• 26 in-tree Ruby gems under gems/ extracted from the monolith.
• Database schema for PostgreSQL 16+ in db/structure.sql (~2.8 MB DDL) and migrations in db/migrate/ and db/post_migrate/.

Companion repositories (not in this repo)

GitLab is delivered as a constellation of related projects whose versions are pinned here via *_VERSION files at the repo root:

• Gitaly — gRPC service for Git storage.
• GitLab Shell — handles SSH push/pull.
• GitLab Pages — static site hosting daemon.
• GitLab KAS — Kubernetes agent server.
• GitLab Zoekt — code search indexer.
• GitLab Elasticsearch Indexer — Elasticsearch indexer.

The pinned versions live in GITALY_SERVER_VERSION, GITLAB_SHELL_VERSION, GITLAB_PAGES_VERSION, GITLAB_KAS_VERSION, GITLAB_ZOEKT_VERSION, GITLAB_ELASTICSEARCH_INDEXER_VERSION, etc.

Where to start in this wiki

• New contributors should read Architecture and Getting started, then How to contribute.
• Backend engineers should browse Systems and Features.
• Frontend engineers should jump to Frontend.
• Database engineers should read Database.
• API consumers should read API.

Editions

Three editions ship from this tree:

• Community Edition (CE) — MIT-licensed, excludes ee/ at build time via the FOSS_ONLY=1 flag.
• Enterprise Edition (EE) — adds the ee/ tree under a proprietary "GitLab Source Available" license.
• JiHu Edition (JH) — a downstream fork tailored for the Chinese market, hosted separately at https://about.gitlab.cn/.

Most code in this repository is shared between CE and EE; the build pipeline strips ee/ to produce CE artifacts.

Software stack

Layer	Technology
Application server	Puma (Ruby on Rails 7.2.3 on Ruby 3.3.10)
Reverse proxy	Workhorse (Go)
Background jobs	Sidekiq
Database	PostgreSQL 16.5+ (multi-database: main + ci + sec + jh)
Cache and queues	Redis 6.0+
OLAP analytics	ClickHouse
Search	Elasticsearch / Zoekt (code search)
Frontend	Vue 2/3, GraphQL via Apollo, Vite + Webpack
Object storage	S3-compatible (Fog)
Git RPC	Gitaly (gRPC)
CI runners	GitLab Runner (separate repo)