gitlab-org--gitlab-foss/doc/administration/geo/replication/external_database.md

# 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

1. SSH into a GitLab **primary** application server and login as root:

   ```shell
   sudo -i
   ```

1. Execute the command below to define the node as **primary** node:

   ```shell
   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](#configure-secondary-application-nodes-to-use-the-external-read-replica) section below.

#### Manually configure the primary database for replication

The [geo_primary_role](https://docs.gitlab.com/omnibus/roles/#gitlab-geo-roles)
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:

```plaintext
##
## 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
```

```plaintext
##
## 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:

```plaintext
##
## 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
```

```plaintext
##
## 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](https://docs.gitlab.com/omnibus/roles/#gitlab-geo-roles)
has three main functions:

1. Configure the replica database.
1. Configure the tracking database.
1. Enable the [Geo Log Cursor](index.md#geo-log-cursor) (not covered in this section).

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

1. SSH into a GitLab **secondary** application server and login as root:

   ```shell
   sudo -i
   ```

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

   ```ruby
   ##
   ## 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>'
   ```

1. Save the file and [reconfigure GitLab](../../restart_gitlab.md#omnibus-gitlab-reconfigure)

### 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](../../reference_architectures/index.md).
If you want to run this database external to Omnibus, please follow the instructions below.

The tracking database requires an [FDW](https://www.postgresql.org/docs/9.6/postgres-fdw.html)
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.

1. 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:

    ```plaintext
    ##
    ## Geo Tracking Database Role
    ## - pg_hba.conf
    ##
    host    all         all               <trusted tracking IP>/32      md5
    host    all         all               <trusted secondary IP>/32     md5
    ```

1. SSH into a GitLab **secondary** server and login as root:

   ```shell
   sudo -i
   ```

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

   ```ruby
   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
   ```

1. Save the file and [reconfigure GitLab](../../restart_gitlab.md#omnibus-gitlab-reconfigure)

1. Run the tracking database migrations:

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

1. Configure the [PostgreSQL FDW](https://www.postgresql.org/docs/9.6/postgres-fdw.html)
   connection and credentials:

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

   ```shell
   #!/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 -U $GEO_DB_USER -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.

1. Save the file and [restart GitLab](../../restart_gitlab.md#omnibus-gitlab-restart)
1. Populate the FDW tables:

   ```shell
   gitlab-rake geo:db:refresh_foreign_tables
   ```