Geo with external PostgreSQL instances (PREMIUM SELF)

This document is relevant if you are using a PostgreSQL instance that is not managed by Omnibus. This includes cloud-managed instances like AWS RDS, or manually installed and configured PostgreSQL instances.

NOTE: We strongly recommend running Omnibus-managed instances as they are actively developed and tested. We aim to be compatible with most external (not managed by Omnibus) databases but we do not guarantee compatibility.

Primary node

SSH into a GitLab primary application server and login as root:
```
sudo -i
```

Edit /etc/gitlab/gitlab.rb and add a unique ID for your node (arbitrary value):

# The unique identifier for the Geo node.
gitlab_rails['geo_node_name'] = '<node_name_here>'

Reconfigure the primary node for the change to take effect:
```
gitlab-ctl reconfigure
```
Execute the command below to define the node as primary node:
```
gitlab-ctl set-geo-primary-node
```
This command will use your defined external_url in /etc/gitlab/gitlab.rb.

Configure the external database to be replicated

To set up an external database, you can either:

Set up streaming replication yourself (for example AWS RDS, bare metal not managed by Omnibus, etc.).
Perform the Omnibus configuration manually as follows.

Leverage your cloud provider's tools to replicate the primary database

Given you have a primary node set up on AWS EC2 that uses RDS. You can now just create a read-only replica in a different region and the replication process will be managed by AWS. Make sure you've set Network ACL, Subnet, and Security Group according to your needs, so the secondary application node can access the database.

The following instructions detail how to create a read-only replica for common cloud providers:

Amazon RDS - Creating a Read Replica
Azure Database for PostgreSQL - Create and manage read replicas in Azure Database for PostgreSQL

Once your read-only replica is set up, you can skip to configure you secondary application node.

Manually configure the primary database for replication

The geo_primary_role configures the primary node's database to be replicated by making changes to pg_hba.conf and postgresql.conf. Make the following configuration changes manually to your external database configuration and ensure that you restart PostgreSQL afterwards for the changes to take effect:

##
## Geo Primary Role
## - pg_hba.conf
##
host    all         all               <trusted primary IP>/32       md5
host    replication gitlab_replicator <trusted primary IP>/32       md5
host    all         all               <trusted secondary IP>/32     md5
host    replication gitlab_replicator <trusted secondary IP>/32     md5

##
## Geo Primary Role
## - postgresql.conf
##
wal_level = hot_standby
max_wal_senders = 10
wal_keep_segments = 50
max_replication_slots = 1 # number of secondary instances
hot_standby = on

Secondary nodes

Manually configure the replica database

Make the following configuration changes manually to your pg_hba.conf and postgresql.conf of your external replica database and ensure that you restart PostgreSQL afterwards for the changes to take effect:

##
## Geo Secondary Role
## - pg_hba.conf
##
host    all         all               <trusted secondary IP>/32     md5
host    replication gitlab_replicator <trusted secondary IP>/32     md5
host    all         all               <trusted primary IP>/24       md5

##
## Geo Secondary Role
## - postgresql.conf
##
wal_level = hot_standby
max_wal_senders = 10
wal_keep_segments = 10
hot_standby = on

Configure secondary application nodes to use the external read-replica

With Omnibus, the geo_secondary_role has three main functions:

Configure the replica database.
Configure the tracking database.
Enable the Geo Log Cursor (not covered in this section).

To configure the connection to the external read-replica database and enable Log Cursor:

SSH into a GitLab secondary application server and login as root:
```
sudo -i
```

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

##
## Geo Secondary role
## - configure dependent flags automatically to enable Geo
##
roles ['geo_secondary_role']

# note this is shared between both databases,
# make sure you define the same password in both
gitlab_rails['db_password'] = '<your_password_here>'

gitlab_rails['db_username'] = 'gitlab'
gitlab_rails['db_host'] = '<database_read_replica_host>'

# Disable the bundled Omnibus PostgreSQL, since we are
# using an external PostgreSQL
postgresql['enable'] = false

Save the file and reconfigure GitLab

Configure the tracking database

Secondary nodes use a separate PostgreSQL installation as a tracking database to keep track of replication status and automatically recover from potential replication issues. Omnibus automatically configures a tracking database when roles ['geo_secondary_role'] is set. If you want to run this database external to Omnibus, please follow the instructions below.

If you are using a cloud-managed service for the tracking database, you may need to grant additional roles to your tracking database user (by default, this is gitlab_geo):

Amazon RDS requires the rds_superuser role.
Azure Database for PostgreSQL requires the azure_pg_admin role.

If you have an external database ready to be used as the tracking database, follow the instructions below to use it:

NOTE: If you want to use AWS RDS as a tracking database, make sure it has access to the secondary database. Unfortunately, just assigning the same security group is not enough as outbound rules do not apply to RDS PostgreSQL databases. Therefore, you need to explicitly add an inbound rule to the read-replica's security group allowing any TCP traffic from the tracking database on port 5432.

Ensure that your secondary node can communicate with your tracking database by manually changing the pg_hba.conf that is associated with your tracking database. Remember to restart PostgreSQL afterwards for the changes to take effect:
```
##
## Geo Tracking Database Role
## - pg_hba.conf
##
host    all         all               <trusted tracking IP>/32      md5
host    all         all               <trusted secondary IP>/32     md5
```
SSH into a GitLab secondary server and login as root:
```
sudo -i
```

Edit /etc/gitlab/gitlab.rb with the connection parameters and credentials for the machine with the PostgreSQL instance:

geo_secondary['db_username'] = 'gitlab_geo'
geo_secondary['db_password'] = '<your_password_here>'

geo_secondary['db_host'] = '<tracking_database_host>'
geo_secondary['db_port'] = <tracking_database_port>      # change to the correct port
geo_postgresql['enable'] = false     # don't use internal managed instance

Save the file and reconfigure GitLab

Run the tracking database migrations:

gitlab-rake geo:db:create
gitlab-rake geo:db:migrate