Multiple Databases (FREE SELF)

Introduced in GitLab 15.7.

WARNING: This feature is not ready for production use

By default, GitLab uses a single application database, referred to as the main database.

To scale GitLab, you can configure GitLab to use multiple application databases.

Due to known issues, configuring GitLab with multiple databases is an Experiment.

After you have set up multiple databases, GitLab uses a second application database for CI/CD features, referred to as the ci database.

All tables have exactly the same structure in both the main, and ci databases. Some examples:

When multiple databases are configured, the ci_pipelines table exists in both the main and ci databases, but GitLab reads and writes only to the ci_pipelines table in the ci database.
Similarly, the projects table exists in both the main and ci databases, but GitLab reads and writes only to the projects table in the main database.
For some tables (such as loose_foreign_keys_deleted_records) GitLab reads and writes to both the main and ci databases. See the development documentation

Known issues

Once data is migrated to the ci database, you cannot migrate it back.

Migrate existing installations

To migrate existing data from the main database to the ci database, you can copy the database across.

Existing source installation

Stop GitLab, except for PostgreSQL:

sudo service gitlab stop
sudo service postgresql start

Dump the main database:

sudo -u git pg_dump -f gitlabhq_production.sql gitlabhq_production

Create the ci database, and copy the data from the previous dump:

sudo -u postgres psql -d template1 -c "CREATE DATABASE gitlabhq_production_ci OWNER git;"
sudo -u git psql -f gitlabhq_production.sql gitlabhq_production_ci

Configure GitLab to use multiple databases.

Existing Omnibus installation

Stop GitLab, except for PostgreSQL:

sudo gitlab-ctl stop
sudo gitlab-ctl start postgresql

Dump the main database:

sudo -u gitlab-psql /opt/gitlab/embedded/bin/pg_dump -h /var/opt/gitlab/postgresql -f gitlabhq_production.sql gitlabhq_production

Create the ci database, and copy the data from the previous dump:

sudo -u gitlab-psql /opt/gitlab/embedded/bin/psql -h /var/opt/gitlab/postgresql -d template1 -c "CREATE DATABASE gitlabhq_production_ci OWNER gitlab;"
sudo -u gitlab-psql  /opt/gitlab/embedded/bin/psql -h /var/opt/gitlab/postgresql -f gitlabhq_production.sql gitlabhq_production_ci

Configure GitLab to use multiple databases.

Set up multiple databases

To configure GitLab to use multiple application databases, follow the instructions below for your installation type.

WARNING: You must stop GitLab before setting up multiple databases. This prevents split-brain situations, where main data is written to the ci database, and the other way around.

Installations from source

For existing installations, migrate the data first.
Back up GitLab in case of unforeseen issues.
Stop GitLab:
```
sudo service gitlab stop
```
Open config/database.yml, and add a ci: section under production:. See config/database.yml.decomposed-postgresql for possible values for this new ci: section. Once modified, the config/database.yml should look like:
```
production:
  main:
    # ...
  ci:
    adapter: postgresql
    encoding: unicode
    database: gitlabhq_production_ci
    # ...
```
Save the config/database.yml file.
Update the service files to set the GITLAB_ALLOW_SEPARATE_CI_DATABASE environment variable to true.

For new installations only. Create the gitlabhq_production_ci database:

sudo -u postgres psql -d template1 -c "CREATE DATABASE gitlabhq_production OWNER git;"
sudo -u git -H bundle exec rake db:schema:load:ci

Lock writes for ci tables in main database, and the other way around:
```
sudo -u git -H bundle exec rake gitlab:db:lock_writes
```
Restart GitLab:
```
sudo service gitlab restart
```

Omnibus GitLab installations

For existing installations, migrate the data first.
Back up GitLab in case of unforeseen issues.
Stop GitLab:
```
sudo gitlab-ctl stop
```

Edit /etc/gitlab/gitlab.rb and add the following lines:

gitlab_rails['env'] = { 'GITLAB_ALLOW_SEPARATE_CI_DATABASE' => 'true' }
gitlab_rails['databases']['ci']['enable'] = true
gitlab_rails['databases']['ci']['db_database'] = 'gitlabhq_production_ci'

Save the /etc/gitlab/gitlab.rb file.
Reconfigure GitLab:
```
sudo gitlab-ctl reconfigure
```

Optional, for new installations only. Reconfiguring GitLab should create the gitlabhq_production_ci database if it does not exist. If the database is not created automatically, create it manually:

sudo gitlab-ctl start postgresql
sudo -u gitlab-psql /opt/gitlab/embedded/bin/psql -h /var/opt/gitlab/postgresql -d template1 -c "CREATE DATABASE gitlabhq_production_ci OWNER gitlab;"
sudo gitlab-rake db:schema:load:ci

Lock writes for ci tables in main database, and the other way around:

sudo gitlab-ctl start postgresql
sudo gitlab-rake gitlab:db:lock_writes

Restart GitLab:
```
sudo gitlab-ctl restart
```

Further information

For more information on multiple databases, see issue 6168.

For more information on how multiple databases work in GitLab, see the development guide for multiple databases.

Since 2022-07-02, GitLab.com has been running with two separate databases. For more information, see this blog post.