183 lines
7.5 KiB
Markdown
183 lines
7.5 KiB
Markdown
# GitLab Architecture Overview
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---
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# Software delivery
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There are two editions of GitLab: [Enterprise Edition](https://www.gitlab.com/gitlab-ee/) (EE) and [Community Edition](https://www.gitlab.com/gitlab-ce/) (CE).
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GitLab CE is delivered via git from the [gitlabhq repository](https://gitlab.com/gitlab-org/gitlab-ce/tree/master).
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New versions of GitLab are released in stable branches and the master branch is for bleeding edge development.
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EE releases are available not long after CE releases.
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To obtain the GitLab EE there is a [repository at gitlab.com](https://gitlab.com/subscribers/gitlab-ee).
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For more information about the release process see the section 'New versions and upgrading' in the readme.
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Both EE and CE require an add-on component called gitlab-shell.
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It is obtained from the [gitlab-shell repository](https://gitlab.com/gitlab-org/gitlab-shell/tree/master).
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New versions are usually tags but staying on the master branch will give you the latest stable version.
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New releases are generally around the same time as GitLab CE releases with exception for informal security updates deemed critical.
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# System Layout
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When referring to ~git in the picures it means the home directory of the git user which is typically /home/git.
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GitLab is primarily installed within the `/home/git` user home directory as `git` user.
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Within the home directory is where the gitlabhq server software resides as well as the repositories (though the repository location is configurable).
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The bare repositories are located in `/home/git/repositories`.
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GitLab is a ruby on rails application so the particulars of the inner workings can be learned by studying how a ruby on rails application works.
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To serve repositories over SSH there's an add-on application called gitlab-shell which is installed in `/home/git/gitlab-shell`.
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## Components
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A typical install of GitLab will be on Ubuntu Linux or RHEL/CentOS.
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It uses Nginx or Apache as a web front end to proxypass the Unicorn web server.
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By default, communication between Unicorn and the front end is via a Unix domain socket but forwarding requests via TCP is also supported.
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The web front end accesses `/home/git/gitlab/public` bypassing the Unicorn server to serve static pages, uploads (e.g. avatar images or attachments), and precompiled assets.
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GitLab serves web pages and a [GitLab API](https://gitlab.com/gitlab-org/gitlab-ce/tree/master/doc/api) using the Unicorn web server.
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It uses Sidekiq as a job queue which, in turn, uses redis as a non-persistent database backend for job information, meta data, and incomming jobs.
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The GitLab web app uses MySQL or PostgreSQL for persistent database information (e.g. users, permissions, issues, other meta data).
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GitLab stores the bare git repositories it serves in `/home/git/repositories` by default.
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It also keeps default branch and hook information with the bare repository.
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`/home/git/gitlab-satellites` keeps checked out repositories when performing actions such as a merge request, editing files in the web interface, etc.
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The satellite repository is used by the web interface for editing repositories and the wiki which is also a git repository.
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When serving repositories over HTTP/HTTPS GitLab utilizes the GitLab API to resolve authorization and access as well as serving git objects.
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The add-on component gitlab-shell serves repositories over SSH.
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It manages the SSH keys within `/home/git/.ssh/authorized_keys` which should not be manually edited.
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gitlab-shell accesses the bare repositories directly to serve git objects and communicates with redis to submit jobs to Sidekiq for GitLab to process.
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gitlab-shell queries the GitLab API to determine authorization and access.
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## Installation Folder Summary
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To summarize here's the [directory structure of the `git` user home directory](../install/structure.md).
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## Processes
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ps aux | grep '^git'
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GitLab has several components to operate.
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As a system user (i.e. any user that is not the `git` user) it requires a persistent database (MySQL/PostreSQL) and redis database.
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It also uses Apache httpd or nginx to proxypass Unicorn.
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As the `git` user it starts Sidekiq and Unicorn (a simple ruby HTTP server running on port `8080` by default).
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Under the gitlab user there are normally 4 processes: `unicorn_rails master` (1 process), `unicorn_rails worker` (2 processes), `sidekiq` (1 process).
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## Repository access
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Repositories get accessed via HTTP or SSH.
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HTTP cloning/push/pull utilizes the GitLab API and SSH cloning is handled by gitlab-shell (previously explained).
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# Troubleshooting
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See the README for more information.
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## Init scripts of the services
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The GitLab init script starts and stops Unicorn and Sidekiq.
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```
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/etc/init.d/gitlab
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Usage: service gitlab {start|stop|restart|reload|status}
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```
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Redis (key-value store/non-persistent database)
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```
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/etc/init.d/redis
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Usage: /etc/init.d/redis {start|stop|status|restart|condrestart|try-restart}
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```
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SSH daemon
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```
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/etc/init.d/sshd
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Usage: /etc/init.d/sshd {start|stop|restart|reload|force-reload|condrestart|try-restart|status}
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```
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Web server (one of the following)
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```
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/etc/init.d/httpd
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Usage: httpd {start|stop|restart|condrestart|try-restart|force-reload|reload|status|fullstatus|graceful|help|configtest}
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$ /etc/init.d/nginx
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Usage: nginx {start|stop|restart|reload|force-reload|status|configtest}
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```
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Persistent database (one of the following)
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```
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/etc/init.d/mysqld
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Usage: /etc/init.d/mysqld {start|stop|status|restart|condrestart|try-restart|reload|force-reload}
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$ /etc/init.d/postgresql
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Usage: /etc/init.d/postgresql {start|stop|restart|reload|force-reload|status} [version ..]
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```
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## Log locations of the services
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Note: `/home/git/` is shorthand for `/home/git`.
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gitlabhq (includes Unicorn and Sidekiq logs)
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* `/home/git/gitlab/log/` contains `application.log`, `production.log`, `sidekiq.log`, `unicorn.stdout.log`, `githost.log`, `satellites.log`, and `unicorn.stderr.log` normally.
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gitlab-shell
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* `/home/git/gitlab-shell/gitlab-shell.log`
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ssh
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* `/var/log/auth.log` auth log (on Ubuntu).
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* `/var/log/secure` auth log (on RHEL).
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nginx
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* `/var/log/nginx/` contains error and access logs.
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Apache httpd
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* [Explanation of apache logs](http://httpd.apache.org/docs/2.2/logs.html).
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* `/var/log/apache2/` contains error and output logs (on Ubuntu).
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* `/var/log/httpd/` contains error and output logs (on RHEL).
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redis
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* `/var/log/redis/redis.log` there are also logrotated logs there.
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PostgreSQL
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* `/var/log/postgresql/*`
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MySQL
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* `/var/log/mysql/*`
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* `/var/log/mysql.*`
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## GitLab specific config files
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GitLab has configuration files located in `/home/git/gitlab/config/*`.
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Commonly referenced config files include:
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* `gitlab.yml` - GitLab configuration.
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* `unicorn.rb` - Unicorn web server settings.
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* `database.yml` - Database connection settings.
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gitlab-shell has a configuration file at `/home/git/gitlab-shell/config.yml`.
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## Maintenance Tasks
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[GitLab](https://gitlab.com/gitlab-org/gitlab-ce/tree/master) provides rake tasks with which you see version information and run a quick check on your configuration to ensure it is configured properly within the application.
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See [maintenance rake tasks](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/raketasks/maintenance.md).
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In a nutshell, do the following:
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```
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sudo -i -u git
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cd gitlab
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bundle exec rake gitlab:env:info RAILS_ENV=production
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bundle exec rake gitlab:check RAILS_ENV=production
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```
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Note: It is recommended to log into the `git` user using `sudo -i -u git` or `sudo su - git`.
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While the sudo commands provided by gitlabhq work in Ubuntu they do not always work in RHEL.
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