Geo with external PostgreSQL instances [PREMIUM ONLY]

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: 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
```
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, in AWS RDS).
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. Skip to the Configure secondary application node section below.

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:

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

##
## Geo Primary Role
## - postgresql.conf
##
sql_replication_user = gitlab_replicator
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 postgresql.conf of external replica database:

##
## 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>'

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. For high availability, refer to Geo High Availability. If you want to run this database external to Omnibus, please follow the instructions below.

The tracking database requires an FDW connection with the secondary replica database for improved performance.

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

NOTE: 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.

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

Edit /etc/gitlab/gitlab.rb with the connection params 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_secondary['db_fdw'] = true       # enable FDW
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

Configure the PostgreSQL FDW connection and credentials:

Save the script below in a file, ex. /tmp/geo_fdw.sh and modify the connection params to match your environment. Execute it to set up the FDW connection.

#!/bin/bash

# Secondary Database connection params:
DB_HOST="<public_ip_or_vpc_private_ip>"
DB_NAME="gitlabhq_production"
DB_USER="gitlab"
DB_PASS="<your_password_here>"
DB_PORT="5432"

# Tracking Database connection params:
GEO_DB_HOST="<public_ip_or_vpc_private_ip>"
GEO_DB_NAME="gitlabhq_geo_production"
GEO_DB_USER="gitlab_geo"
GEO_DB_PORT="5432"

query_exec () {
  gitlab-psql -h $GEO_DB_HOST -d $GEO_DB_NAME -p $GEO_DB_PORT -c "${1}"
}

query_exec "CREATE EXTENSION postgres_fdw;"
query_exec "CREATE SERVER gitlab_secondary FOREIGN DATA WRAPPER postgres_fdw OPTIONS (host '${DB_HOST}', dbname '${DB_NAME}', port '${DB_PORT}');"
query_exec "CREATE USER MAPPING FOR ${GEO_DB_USER} SERVER gitlab_secondary OPTIONS (user '${DB_USER}', password '${DB_PASS}');"
query_exec "CREATE SCHEMA gitlab_secondary;"
query_exec "GRANT USAGE ON FOREIGN SERVER gitlab_secondary TO ${GEO_DB_USER};"

NOTE: Note: The script template above uses gitlab-psql as it's intended to be executed from the Geo machine, but you can change it to psql and run it from any machine that has access to the database. We also recommend using psql for AWS RDS.

Save the file and restart GitLab

Populate the FDW tables:

gitlab-rake geo:db:refresh_foreign_tables

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