ClickHouse integration guidelines

DETAILS: Status: Experiment

This feature is an experiment.

Instructions about how to set up integration between GitLab and ClickHouse database.

Setup

To set up ClickHouse as the GitLab data storage:

Run ClickHouse Cluster and configure database.
Configure GitLab connection to Clickhouse.
Run ClickHouse migrations.

Run and configure ClickHouse

The most straightforward way to run ClickHouse is with ClickHouse Cloud. You can also run ClickHouse on your own server. Refer to the ClickHouse documentation regarding recommendations for self-managed instances.

When you run ClickHouse on a hosted server, various data points might impact the resource consumption, like the number of builds that run on your instance each month, the selected hardware, the data center choice to host ClickHouse, and more. Regardless, the cost should not be significant.

NOTE: ClickHouse is a secondary data store for GitLab. Only specific data is stored in ClickHouse for analytics purposes.

To create necessary user and database objects:

Generate a secure password and save it.
Sign in to the ClickHouse SQL console.

Execute the following command. Replace PASSWORD_HERE with the generated password.

CREATE DATABASE gitlab_clickhouse_main_production;
CREATE USER gitlab IDENTIFIED WITH sha256_password BY 'PASSWORD_HERE';
CREATE ROLE gitlab_app;
GRANT SELECT, INSERT, ALTER, CREATE, UPDATE, DROP, TRUNCATE, OPTIMIZE ON gitlab_clickhouse_main_production.* TO gitlab_app;
GRANT SELECT ON information_schema.* TO gitlab_app;
GRANT gitlab_app TO gitlab;

Configure the GitLab connection to ClickHouse

::Tabs

:::TabTitle Linux package

To provide GitLab with ClickHouse credentials:

Edit /etc/gitlab/gitlab.rb:

 gitlab_rails['clickhouse_databases']['main']['database'] = 'gitlab_clickhouse_main_production'
 gitlab_rails['clickhouse_databases']['main']['url'] = 'https://example.com/path'
 gitlab_rails['clickhouse_databases']['main']['username'] = 'gitlab'
 gitlab_rails['clickhouse_databases']['main']['password'] = 'PASSWORD_HERE' # replace with the actual password

Save the file and reconfigure GitLab:
```
sudo gitlab-ctl reconfigure
```

:::TabTitle Helm chart (Kubernetes)

Save the ClickHouse password as a Kubernetes Secret:

kubectl create secret generic gitlab-clickhouse-password --from-literal="main_password=PASSWORD_HERE"

Export the Helm values:

helm get values gitlab > gitlab_values.yaml

Edit gitlab_values.yaml:

global:
  clickhouse:
    enabled: true
    main:
      username: default
      password:
        secret: gitlab-clickhouse-password
        key: main_password
      database: gitlab_clickhouse_main_production
      url: 'http://example.com'

Save the file and apply the new values:

helm upgrade -f gitlab_values.yaml gitlab gitlab/gitlab

::EndTabs

To verify that your connection is set up successfully:

Sign in to Rails console
Execute the following:
```
ClickHouse::Client.select('SELECT 1', :main)
```
If successful, the command returns [{"1"=>1}]

Run ClickHouse migrations

To create the required database objects execute:

sudo gitlab-rake gitlab:clickhouse:migrate