# Configuring GitLab Scaling and High Availability

> **Note:** There is some additional configuration near the bottom for
  additional GitLab application servers. It's important to read and understand
  these additional steps before proceeding with GitLab installation.

1. If necessary, install the NFS client utility packages using the following
   commands:

    ```
    # Ubuntu/Debian
    apt-get install nfs-common

    # CentOS/Red Hat
    yum install nfs-utils nfs-utils-lib
    ```

1. Specify the necessary NFS shares. Mounts are specified in
   `/etc/fstab`. The exact contents of `/etc/fstab` will depend on how you chose
   to configure your NFS server. See [NFS documentation](nfs.md) for the various
   options. Here is an example snippet to add to `/etc/fstab`:

    ```
    10.1.0.1:/var/opt/gitlab/.ssh /var/opt/gitlab/.ssh nfs4 defaults,soft,rsize=1048576,wsize=1048576,noatime,nofail,lookupcache=positive 0 2
    10.1.0.1:/var/opt/gitlab/gitlab-rails/uploads /var/opt/gitlab/gitlab-rails/uploads nfs4 defaults,soft,rsize=1048576,wsize=1048576,noatime,nofail,lookupcache=positive 0 2
    10.1.0.1:/var/opt/gitlab/gitlab-rails/shared /var/opt/gitlab/gitlab-rails/shared nfs4 defaults,soft,rsize=1048576,wsize=1048576,noatime,nofail,lookupcache=positive 0 2
    10.1.0.1:/var/opt/gitlab/gitlab-ci/builds /var/opt/gitlab/gitlab-ci/builds nfs4 defaults,soft,rsize=1048576,wsize=1048576,noatime,nofail,lookupcache=positive 0 2
    10.1.0.1:/var/opt/gitlab/git-data /var/opt/gitlab/git-data nfs4 defaults,soft,rsize=1048576,wsize=1048576,noatime,nofail,lookupcache=positive 0 2
    ```

1. Create the shared directories. These may be different depending on your NFS
   mount locations.

    ```
    mkdir -p /var/opt/gitlab/.ssh /var/opt/gitlab/gitlab-rails/uploads /var/opt/gitlab/gitlab-rails/shared /var/opt/gitlab/gitlab-ci/builds /var/opt/gitlab/git-data
    ```

1. Download/install GitLab Omnibus using **steps 1 and 2** from
   [GitLab downloads](https://about.gitlab.com/downloads). Do not complete other
   steps on the download page.
1. Create/edit `/etc/gitlab/gitlab.rb` and use the following configuration.
   Be sure to change the `external_url` to match your eventual GitLab front-end
   URL. Depending your the NFS configuration, you may need to change some GitLab
   data locations. See [NFS documentation](nfs.md) for `/etc/gitlab/gitlab.rb`
   configuration values for various scenarios. The example below assumes you've
   added NFS mounts in the default data locations. Additionally the UID and GIDs
   given are just examples and you should configure with your preferred values.

    ```ruby
    external_url 'https://gitlab.example.com'

    # Prevent GitLab from starting if NFS data mounts are not available
    high_availability['mountpoint'] = '/var/opt/gitlab/git-data'

    # Disable components that will not be on the GitLab application server
    roles ['application_role']
    nginx['enable'] = true

    # PostgreSQL connection details
    gitlab_rails['db_adapter'] = 'postgresql'
    gitlab_rails['db_encoding'] = 'unicode'
    gitlab_rails['db_host'] = '10.1.0.5' # IP/hostname of database server
    gitlab_rails['db_password'] = 'DB password'

    # Redis connection details
    gitlab_rails['redis_port'] = '6379'
    gitlab_rails['redis_host'] = '10.1.0.6' # IP/hostname of Redis server
    gitlab_rails['redis_password'] = 'Redis Password'
    
    # Ensure UIDs and GIDs match between servers for permissions via NFS
    user['uid'] = 9000
    user['gid'] = 9000
    web_server['uid'] = 9001
    web_server['gid'] = 9001
    registry['uid'] = 9002
    registry['gid'] = 9002
    ```

    > **Note:** To maintain uniformity of links across HA clusters, the `external_url`
    on the first application server as well as the additional application
    servers should point to the external url that users will use to access GitLab.
    In a typical HA setup, this will be the url of the load balancer which will
    route traffic to all GitLab application servers in the HA cluster.
    > 
    > **Note:** When you specify `https` in the `external_url`, as in the example
    above, GitLab assumes you have SSL certificates in `/etc/gitlab/ssl/`. If
    certificates are not present, Nginx will fail to start. See
    [Nginx documentation](http://docs.gitlab.com/omnibus/settings/nginx.html#enable-https)
    for more information.
    >
    > **Note:** It is best to set the `uid` and `gid`s prior to the initial reconfigure of GitLab. Omnibus will not recursively `chown` directories if set after the initial reconfigure.

## First GitLab application server

As a final step, run the setup rake task **only on** the first GitLab application server.
Do not run this on additional application servers.

1. Initialize the database by running `sudo gitlab-rake gitlab:setup`.
1. Run `sudo gitlab-ctl reconfigure` to compile the configuration.

> **WARNING:** Only run this setup task on **NEW** GitLab instances because it
  will wipe any existing data.

## Extra configuration for additional GitLab application servers

Additional GitLab servers (servers configured **after** the first GitLab server)
need some extra configuration.

1. Configure shared secrets. These values can be obtained from the primary
   GitLab server in `/etc/gitlab/gitlab-secrets.json`. Copy this file to the
   secondary servers **prior to** running the first `reconfigure` in the steps
   above.

    ```ruby
    gitlab_shell['secret_token'] = 'fbfb19c355066a9afb030992231c4a363357f77345edd0f2e772359e5be59b02538e1fa6cae8f93f7d23355341cea2b93600dab6d6c3edcdced558fc6d739860'
    gitlab_rails['otp_key_base'] = 'b719fe119132c7810908bba18315259ed12888d4f5ee5430c42a776d840a396799b0a5ef0a801348c8a357f07aa72bbd58e25a84b8f247a25c72f539c7a6c5fa'
    gitlab_rails['secret_key_base'] = '6e657410d57c71b4fc3ed0d694e7842b1895a8b401d812c17fe61caf95b48a6d703cb53c112bc01ebd197a85da81b18e29682040e99b4f26594772a4a2c98c6d'
    gitlab_rails['db_key_base'] = 'bf2e47b68d6cafaef1d767e628b619365becf27571e10f196f98dc85e7771042b9203199d39aff91fcb6837c8ed83f2a912b278da50999bb11a2fbc0fba52964'
    ```

1. Run `touch /etc/gitlab/skip-auto-reconfigure` to prevent database migrations
   from running on upgrade. Only the primary GitLab application server should
   handle migrations.

1. **Optional** Configure host keys. Copy all contents(primary and public keys) inside `/etc/ssh/` on
   the primary application server to `/etc/ssh` on all secondary servers. This
   prevents false man-in-the-middle-attack alerts when accessing servers in your
   High Availability cluster behind a load balancer.

1. Run `sudo gitlab-ctl reconfigure` to compile the configuration.

## Troubleshooting

- `mount: wrong fs type, bad option, bad superblock on`

You have not installed the necessary NFS client utilities. See step 1 above.

- `mount: mount point /var/opt/gitlab/... does not exist`

This particular directory does not exist on the NFS server. Ensure
the share is exported and exists on the NFS server and try to remount.

---

## Upgrading GitLab HA

GitLab HA installations can be upgraded with no downtime, but the
upgrade process must be carefully coordinated to avoid failures. See the
[Omnibus GitLab multi-node upgrade
document](https://docs.gitlab.com/omnibus/update/#multi-node--ha-deployment)
for more details.

Read more on high-availability configuration:

1. [Configure the database](database.md)
1. [Configure Redis](redis.md)
1. [Configure NFS](nfs.md)
1. [Configure the load balancers](load_balancer.md)
