Add instructions for enabling the tracking DB for Geo

[ci skip]

doc/gitlab-geo/configuration.md

@@ -147,6 +147,34 @@ sensitive data in the database. Any secondary node must have the
     sudo -i
     ```
 
+1. Edit the /etc/gitlab/gitlab.rb:
+
+    ```
+    geo_secondary_role['enable'] = true
+    geo_postgresql['enable'] = true
+    ```
+
+1. Create `database_geo.yml` with the information of your secondary PostgreSQL
+   database.  Note that GitLab will set up another database instance separate
+   from the primary, since this is where the secondary will track its internal
+   state:
+
+    ```
+    sudo cp /opt/gitlab/embedded/service/gitlab-rails/config/database_geo.yml.postgresql /opt/gitlab/embedded/service/gitlab-rails/config/database_geo.yml
+    ```
+
+1. Reconfigure GitLab:
+
+    ```
+    sudo gitlab-ctl reconfigure
+    ```
+
+1. Set up the Geo tracking database:
+
+    ```
+    sudo gitlab-rake geo:db:setup
+    ```
+
 1. Create a new SSH key pair for the secondary node. Choose the default location
    and leave the password blank by hitting 'Enter' three times:
 

doc/gitlab-geo/configuration_source.md

@@ -33,6 +33,7 @@ next steps can be summed up to:
 
 1. Configure the primary node
 1. Replicate some required configurations between the primary and the secondaries
+1. Configure a second, tracking database for each secondary
 1. Start GitLab in the secondary node's machine
 1. Configure every secondary node in the primary's Admin screen
 
@@ -46,6 +47,9 @@ first two steps of the [Setup instructions](README.md#setup-instructions):
 1. You have set up the database replication.
 1. Your secondary node is allowed to communicate via HTTP/HTTPS and SSH with
    your primary node (make sure your firewall is not blocking that).
+1. You have set up another PostgreSQL database that can store writes for the secondary.
+   Note that this MUST be on another instance, since the primary replicated database
+   is read-only.
 
 Some of the following steps require to configure the primary and secondary
 nodes almost at the same time. For your convenience make sure you have SSH
@@ -136,6 +140,20 @@ sensitive data in the database. Any secondary node must have the
     sudo -i
     ```
 
+1. Create `database_geo.yml` with the information of your secondary PostgreSQL database.
+   Note that this must be a totally different instance from the primary, since this
+   is where the secondary will track its internal state:
+
+    ```
+    sudo cp /home/git/gitlab/config/database_geo.yml.postgresql /home/git/gitlab/config/database_geo.yml
+    ```
+
+1. Set up the Geo tracking database:
+
+    ```
+    bundle exec rake geo:db:setup
+    ```
+
 1. Open the secrets file and paste the value of `db_key_base` you copied in the
    previous step: