---
stage: Enablement
group: Geo
info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
type: howto
---

# Geo database replication **(PREMIUM SELF)**

This document describes the minimal required steps to replicate your primary
GitLab database to a secondary node's database. You may have to change some
values, based on attributes including your database's setup and size.

NOTE:
If your GitLab installation uses external (not managed by Omnibus GitLab)
PostgreSQL instances, the Omnibus roles cannot perform all necessary
configuration steps. In this case, use the [Geo with external PostgreSQL instances](external_database.md)
process instead.

The stages of the setup process must be completed in the documented order.
Before you attempt the steps in this stage, [complete all prior stages](../setup/index.md#using-omnibus-gitlab).

Be sure to read and review all of these steps before you execute them in your
testing or production environments.

## Single instance database replication

A single instance database replication is easier to set up and still provides the same Geo capabilities
as a clusterized alternative. It's useful for setups running on a single machine
or trying to evaluate Geo for a future clusterized installation.

A single instance can be expanded to a clusterized version using Patroni, which is recommended for a
highly available architecture.

Follow below the instructions on how to set up PostgreSQL replication as a single instance database.
Alternatively, you can look at the [Multi-node database replication](#multi-node-database-replication)
instructions on setting up replication with a Patroni cluster.

### PostgreSQL replication

The GitLab **primary** node where the write operations happen connects to
the **primary** database server, and **secondary** nodes
connect to their own database servers (which are read-only).

We recommend using [PostgreSQL replication slots](https://medium.com/@tk512/replication-slots-in-postgresql-b4b03d277c75)
to ensure that the **primary** node retains all the data necessary for the **secondary** nodes to
recover. See below for more details.

The following guide assumes that:

- You are using Omnibus and therefore you are using PostgreSQL 12 or later
  which includes the [`pg_basebackup` tool](https://www.postgresql.org/docs/12/app-pgbasebackup.html).
- You have a **primary** node already set up (the GitLab server you are
  replicating from), running Omnibus' PostgreSQL (or equivalent version), and
  you have a new **secondary** server set up with the same versions of the OS,
  PostgreSQL, and GitLab on all nodes.

WARNING:
Geo works with streaming replication. Logical replication is not supported at this time.
There is an [issue where support is being discussed](https://gitlab.com/gitlab-org/gitlab/-/issues/7420).

#### Step 1. Configure the **primary** server

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

   ```shell
   sudo -i
   ```

1. Edit `/etc/gitlab/gitlab.rb` and add a **unique** name for your site:

   ```ruby
   ##
   ## The unique identifier for the Geo site. See
   ## https://docs.gitlab.com/ee/user/admin_area/geo_nodes.html#common-settings
   ##
   gitlab_rails['geo_node_name'] = '<site_name_here>'
   ```

1. Reconfigure the **primary** node for the change to take effect:

   ```shell
   gitlab-ctl reconfigure
   ```

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

   ```shell
   gitlab-ctl set-geo-primary-node
   ```

   This command uses your defined `external_url` in `/etc/gitlab/gitlab.rb`.

1. Define a password for the `gitlab` database user:

   Generate a MD5 hash of the desired password:

   ```shell
   gitlab-ctl pg-password-md5 gitlab
   # Enter password: <your_password_here>
   # Confirm password: <your_password_here>
   # fca0b89a972d69f00eb3ec98a5838484
   ```

   Edit `/etc/gitlab/gitlab.rb`:

   ```ruby
   # Fill with the hash generated by `gitlab-ctl pg-password-md5 gitlab`
   postgresql['sql_user_password'] = '<md5_hash_of_your_password>'

   # Every node that runs Puma or Sidekiq needs to have the database
   # password specified as below. If you have a high-availability setup, this
   # must be present in all application nodes.
   gitlab_rails['db_password'] = '<your_password_here>'
   ```

1. Define a password for the database [replication user](https://wiki.postgresql.org/wiki/Streaming_Replication).

   We will use the username defined in `/etc/gitlab/gitlab.rb` under the `postgresql['sql_replication_user']`
   setting. The default value is `gitlab_replicator`, but if you changed it to something else, adapt
   the instructions below.

   Generate a MD5 hash of the desired password:

   ```shell
   gitlab-ctl pg-password-md5 gitlab_replicator
   # Enter password: <your_password_here>
   # Confirm password: <your_password_here>
   # 950233c0dfc2f39c64cf30457c3b7f1e
   ```

   Edit `/etc/gitlab/gitlab.rb`:

   ```ruby
   # Fill with the hash generated by `gitlab-ctl pg-password-md5 gitlab_replicator`
   postgresql['sql_replication_password'] = '<md5_hash_of_your_password>'
   ```

   If you are using an external database not managed by Omnibus GitLab, you need
   to create the replicator user and define a password to it manually:

   ```sql
   --- Create a new user 'replicator'
   CREATE USER gitlab_replicator;

   --- Set/change a password and grants replication privilege
   ALTER USER gitlab_replicator WITH REPLICATION ENCRYPTED PASSWORD '<replication_password>';
   ```

1. Configure PostgreSQL to listen on network interfaces:

   For security reasons, PostgreSQL does not listen on any network interfaces
   by default. However, Geo requires the **secondary** node to be able to
   connect to the **primary** node's database. For this reason, we need the address of
   each node.

   NOTE:
   For external PostgreSQL instances, see [additional instructions](external_database.md).

   If you are using a cloud provider, you can lookup the addresses for each
   Geo node through your cloud provider's management console.

   To lookup the address of a Geo node, SSH in to the Geo node and execute:

   ```shell
   ##
   ## Private address
   ##
   ip route get 255.255.255.255 | awk '{print "Private address:", $NF; exit}'

   ##
   ## Public address
   ##
   echo "External address: $(curl --silent "ipinfo.io/ip")"
   ```

   In most cases, the following addresses are used to configure GitLab
   Geo:

   | Configuration                           | Address                                               |
   |:----------------------------------------|:------------------------------------------------------|
   | `postgresql['listen_address']`          | **Primary** node's public or VPC private address.     |
   | `postgresql['md5_auth_cidr_addresses']` | **Secondary** node's public or VPC private addresses. |

   If you are using Google Cloud Platform, SoftLayer, or any other vendor that
   provides a virtual private cloud (VPC) you can use the **primary** and **secondary** nodes
   private addresses (corresponds to "internal address" for Google Cloud Platform) for
   `postgresql['md5_auth_cidr_addresses']` and `postgresql['listen_address']`.

   The `listen_address` option opens PostgreSQL up to network connections with the interface
   corresponding to the given address. See [the PostgreSQL documentation](https://www.postgresql.org/docs/12/runtime-config-connection.html)
   for more details.

   NOTE:
   If you need to use `0.0.0.0` or `*` as the listen_address, you also need to add
   `127.0.0.1/32` to the `postgresql['md5_auth_cidr_addresses']` setting, to allow Rails to connect through
   `127.0.0.1`. For more information, see [omnibus-5258](https://gitlab.com/gitlab-org/omnibus-gitlab/-/issues/5258).

   Depending on your network configuration, the suggested addresses may not
   be correct. If your **primary** node and **secondary** nodes connect over a local
   area network, or a virtual network connecting availability zones like
   [Amazon's VPC](https://aws.amazon.com/vpc/) or [Google's VPC](https://cloud.google.com/vpc/)
   you should use the **secondary** node's private address for `postgresql['md5_auth_cidr_addresses']`.

   Edit `/etc/gitlab/gitlab.rb` and add the following, replacing the IP
   addresses with addresses appropriate to your network configuration:

   ```ruby
   ##
   ## Geo Primary role
   ## - Configures Postgres settings for replication
   ## - Prevents automatic upgrade of Postgres since it requires downtime of
   ##   streaming replication to Geo secondary sites
   ## - Enables standard single-node GitLab services like NGINX, Puma, Redis,
   ##   or Sidekiq. If you are segregating services, then you will need to
   ##   explicitly disable unwanted services.
   ##
   roles(['geo_primary_role'])

   ##
   ## Primary address
   ## - replace '<primary_node_ip>' with the public or VPC address of your Geo primary node
   ##
   postgresql['listen_address'] = '<primary_node_ip>'

   ##
   # Allow PostgreSQL client authentication from the primary and secondary IPs. These IPs may be
   # public or VPC addresses in CIDR format, for example ['198.51.100.1/32', '198.51.100.2/32']
   ##
   postgresql['md5_auth_cidr_addresses'] = ['<primary_node_ip>/32', '<secondary_node_ip>/32']

   ##
   ## Replication settings
   ## - set this to be the number of Geo secondary nodes you have
   ##
   postgresql['max_replication_slots'] = 1
   # postgresql['max_wal_senders'] = 10
   # postgresql['wal_keep_segments'] = 10

   ##
   ## Disable automatic database migrations temporarily
   ## (until PostgreSQL is restarted and listening on the private address).
   ##
   gitlab_rails['auto_migrate'] = false
   ```

1. Optional: If you want to add another **secondary** node, the relevant setting would look like:

   ```ruby
   postgresql['md5_auth_cidr_addresses'] = ['<primary_node_ip>/32', '<secondary_node_ip>/32', '<another_secondary_node_ip>/32']
   ```

   You may also want to edit the `wal_keep_segments` and `max_wal_senders` to match your
   database replication requirements. Consult the [PostgreSQL - Replication documentation](https://www.postgresql.org/docs/12/runtime-config-replication.html)
   for more information.

1. Save the file and reconfigure GitLab for the database listen changes and
   the replication slot changes to be applied:

   ```shell
   gitlab-ctl reconfigure
   ```

   Restart PostgreSQL for its changes to take effect:

   ```shell
   gitlab-ctl restart postgresql
   ```

1. Re-enable migrations now that PostgreSQL is restarted and listening on the
   private address.

   Edit `/etc/gitlab/gitlab.rb` and **change** the configuration to `true`:

   ```ruby
   gitlab_rails['auto_migrate'] = true
   ```

   Save the file and reconfigure GitLab:

   ```shell
   gitlab-ctl reconfigure
   ```

1. Now that the PostgreSQL server is set up to accept remote connections, run
   `netstat -plnt | grep 5432` to make sure that PostgreSQL is listening on port
   `5432` to the **primary** server's private address.

1. A certificate was automatically generated when GitLab was reconfigured. This
   is used automatically to protect your PostgreSQL traffic from
   eavesdroppers, but to protect against active ("man-in-the-middle") attackers,
   the **secondary** node needs a copy of the certificate. Make a copy of the PostgreSQL
   `server.crt` file on the **primary** node by running this command:

   ```shell
   cat ~gitlab-psql/data/server.crt
   ```

   Copy the output into a clipboard or into a local file. You
   need it when setting up the **secondary** node! The certificate is not sensitive
   data.

#### Step 2. Configure the **secondary** server

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

   ```shell
   sudo -i
   ```

1. Stop application server and Sidekiq

   ```shell
   gitlab-ctl stop puma
   gitlab-ctl stop sidekiq
   ```

   NOTE:
   This step is important so we don't try to execute anything before the node is fully configured.

1. [Check TCP connectivity](../../raketasks/maintenance.md) to the **primary** node's PostgreSQL server:

   ```shell
   gitlab-rake gitlab:tcp_check[<primary_node_ip>,5432]
   ```

   NOTE:
   If this step fails, you may be using the wrong IP address, or a firewall may
   be preventing access to the server. Check the IP address, paying close
   attention to the difference between public and private addresses and ensure
   that, if a firewall is present, the **secondary** node is permitted to connect to the
   **primary** node on port 5432.

1. Create a file `server.crt` in the **secondary** server, with the content you got on the last step of the **primary** node's setup:

   ```shell
   editor server.crt
   ```

1. Set up PostgreSQL TLS verification on the **secondary** node:

   Install the `server.crt` file:

   ```shell
   install \
      -D \
      -o gitlab-psql \
      -g gitlab-psql \
      -m 0400 \
      -T server.crt ~gitlab-psql/.postgresql/root.crt
   ```

   PostgreSQL now only recognizes that exact certificate when verifying TLS
   connections. The certificate can only be replicated by someone with access
   to the private key, which is **only** present on the **primary** node.

1. Test that the `gitlab-psql` user can connect to the **primary** node's database
   (the default Omnibus database name is `gitlabhq_production`):

   ```shell
   sudo \
      -u gitlab-psql /opt/gitlab/embedded/bin/psql \
      --list \
      -U gitlab_replicator \
      -d "dbname=gitlabhq_production sslmode=verify-ca" \
      -W \
      -h <primary_node_ip>
   ```

   When prompted enter the password you set in the first step for the
   `gitlab_replicator` user. If all worked correctly, you should see
   the list of **primary** node's databases.

   A failure to connect here indicates that the TLS configuration is incorrect.
   Ensure that the contents of `~gitlab-psql/data/server.crt` on the **primary** node
   match the contents of `~gitlab-psql/.postgresql/root.crt` on the **secondary** node.

1. Configure PostgreSQL:

   This step is similar to how we configured the **primary** instance.
   We need to enable this, even if using a single node.

   Edit `/etc/gitlab/gitlab.rb` and add the following, replacing the IP
   addresses with addresses appropriate to your network configuration:

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

   ##
   ## Secondary address
   ## - replace '<secondary_node_ip>' with the public or VPC address of your Geo secondary node
   ##
   postgresql['listen_address'] = '<secondary_node_ip>'
   postgresql['md5_auth_cidr_addresses'] = ['<secondary_node_ip>/32']

   ##
   ## Database credentials password (defined previously in primary node)
   ## - replicate same values here as defined in primary node
   ##
   postgresql['sql_replication_password'] = '<md5_hash_of_your_password>'
   postgresql['sql_user_password'] = '<md5_hash_of_your_password>'
   gitlab_rails['db_password'] = '<your_password_here>'
   ```

   For external PostgreSQL instances, see [additional instructions](external_database.md).
   If you bring a former **primary** node back online to serve as a **secondary** node, then you also need to remove `roles(['geo_primary_role'])` or `geo_primary_role['enable'] = true`.

1. Reconfigure GitLab for the changes to take effect:

   ```shell
   gitlab-ctl reconfigure
   ```

1. Restart PostgreSQL for the IP change to take effect:

   ```shell
   gitlab-ctl restart postgresql
   ```

#### Step 3. Initiate the replication process

Below we provide a script that connects the database on the **secondary** node to
the database on the **primary** node, replicates the database, and creates the
needed files for streaming replication.

The directories used are the defaults that are set up in Omnibus. If you have
changed any defaults, configure it as you see fit replacing the directories and paths.

WARNING:
Make sure to run this on the **secondary** server as it removes all PostgreSQL's
data before running `pg_basebackup`.

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

   ```shell
   sudo -i
   ```

1. Choose a database-friendly name to use for your **secondary** node to
   use as the replication slot name. For example, if your domain is
   `secondary.geo.example.com`, you may use `secondary_example` as the slot
   name as shown in the commands below.

1. Execute the command below to start a backup/restore and begin the replication

   WARNING:
   Each Geo **secondary** node must have its own unique replication slot name.
   Using the same slot name between two secondaries breaks PostgreSQL replication.

   ```shell
   gitlab-ctl replicate-geo-database \
      --slot-name=<secondary_node_name> \
      --host=<primary_node_ip>
   ```

   NOTE:
   Replication slot names must only contain lowercase letters, numbers, and the underscore character.

   When prompted, enter the _plaintext_ password you set up for the `gitlab_replicator`
   user in the first step.

   This command also takes a number of additional options. You can use `--help`
   to list them all, but here are a couple of tips:

   - If PostgreSQL is listening on a non-standard port, add `--port=` as well.
   - If your database is too large to be transferred in 30 minutes, you need
     to increase the timeout, for example, `--backup-timeout=3600` if you expect the
     initial replication to take under an hour.
   - Pass `--sslmode=disable` to skip PostgreSQL TLS authentication altogether
     (for example, you know the network path is secure, or you are using a site-to-site
     VPN). This is **not** safe over the public Internet!
   - You can read more details about each `sslmode` in the
     [PostgreSQL documentation](https://www.postgresql.org/docs/12/libpq-ssl.html#LIBPQ-SSL-PROTECTION);
     the instructions above are carefully written to ensure protection against
     both passive eavesdroppers and active "man-in-the-middle" attackers.
   - Change the `--slot-name` to the name of the replication slot
     to be used on the **primary** database. The script attempts to create the
     replication slot automatically if it does not exist.
   - If you're repurposing an old server into a Geo **secondary** node, you need to
     add `--force` to the command line.
   - When not in a production machine you can disable backup step if you
     really sure this is what you want by adding `--skip-backup`

The replication process is now complete.

### PgBouncer support (optional)

[PgBouncer](https://www.pgbouncer.org/) may be used with GitLab Geo to pool
PostgreSQL connections, which can improve performance even when using in a
single instance installation.

We recommend using PgBouncer if you use GitLab in a highly available
configuration with a cluster of nodes supporting a Geo **primary** site and
two other clusters of nodes supporting a Geo **secondary** site. One for the
main database and the other for the tracking database. For more information,
see [High Availability with Omnibus GitLab](../../postgresql/replication_and_failover.md).

### Changing the replication password

To change the password for the [replication user](https://wiki.postgresql.org/wiki/Streaming_Replication)
when using Omnibus-managed PostgreSQL instances:

On the GitLab Geo **primary** server:

1. The default value for the replication user is `gitlab_replicator`, but if you've set a custom replication
   user in your `/etc/gitlab/gitlab.rb` under the `postgresql['sql_replication_user']` setting, make sure to
   adapt the following instructions for your own user.

   Generate an MD5 hash of the desired password:

   ```shell
   sudo gitlab-ctl pg-password-md5 gitlab_replicator
   # Enter password: <your_password_here>
   # Confirm password: <your_password_here>
   # 950233c0dfc2f39c64cf30457c3b7f1e
   ```

   Edit `/etc/gitlab/gitlab.rb`:

   ```ruby
   # Fill with the hash generated by `gitlab-ctl pg-password-md5 gitlab_replicator`
   postgresql['sql_replication_password'] = '<md5_hash_of_your_password>'
   ```

1. Save the file and reconfigure GitLab to change the replication user's password in PostgreSQL:

   ```shell
   sudo gitlab-ctl reconfigure
   ```

1. Restart PostgreSQL for the replication password change to take effect:

   ```shell
   sudo gitlab-ctl restart postgresql
   ```

Until the password is updated on any **secondary** servers, the [PostgreSQL log](../../logs.md#postgresql-logs) on
the secondaries will report the following error message:

```console
FATAL:  could not connect to the primary server: FATAL:  password authentication failed for user "gitlab_replicator"
```

On all GitLab Geo **secondary** servers:

1. The first step isn't necessary from a configuration perspective, since the hashed `'sql_replication_password'`
   is not used on the GitLab Geo **secondary**. However in the event that **secondary** needs to be promoted
   to the GitLab Geo **primary**, make sure to match the `'sql_replication_password'` in the secondary
   server configuration.

   Edit `/etc/gitlab/gitlab.rb`:

   ```ruby
   # Fill with the hash generated by `gitlab-ctl pg-password-md5 gitlab_replicator` on the Geo primary
   postgresql['sql_replication_password'] = '<md5_hash_of_your_password>'
   ```

1. During the initial replication setup, the `gitlab-ctl replicate-geo-database` command writes the plaintext
   password for the replication user account to two locations:

   - `gitlab-geo.conf`: Used by the PostgreSQL replication process, written to the PostgreSQL data
      directory, by default at `/var/opt/gitlab/postgresql/data/gitlab-geo.conf`.
   - `.pgpass`: Used by the `gitlab-psql` user, located by default at `/var/opt/gitlab/postgresql/.pgpass`.

   Update the plaintext password in both of these files, and restart PostgreSQL:

   ```shell
   sudo gitlab-ctl restart postgresql
   ```

## Multi-node database replication

In GitLab 14.0, Patroni replaced `repmgr` as the supported
[highly available PostgreSQL solution](../../postgresql/replication_and_failover.md).

NOTE:
If you still haven't [migrated from repmgr to Patroni](#migrating-from-repmgr-to-patroni) you're highly advised to do so.

### Patroni support

Patroni is the official replication management solution for Geo. It
can be used to build a highly available cluster on the **primary** and a **secondary** Geo site.
Using Patroni on a **secondary** site is optional and you don't have to use the same amount of
nodes on each Geo site.

For instructions about how to set up Patroni on the primary site, see the
[PostgreSQL replication and failover with Omnibus GitLab](../../postgresql/replication_and_failover.md#patroni) page.

#### Configuring Patroni cluster for a Geo secondary site

In a Geo secondary site, the main PostgreSQL database is a read-only replica of the primary site's PostgreSQL database.

If you are currently using `repmgr` on your Geo primary site, see [these instructions](#migrating-from-repmgr-to-patroni)
for migrating from `repmgr` to Patroni.

A production-ready and secure setup requires at least:

- 3 Consul nodes _(primary and secondary sites)_
- 2 Patroni nodes _(primary and secondary sites)_
- 1 PgBouncer node _(primary and secondary sites)_
- 1 internal load-balancer _(primary site only)_

The internal load balancer provides a single endpoint for connecting to the Patroni cluster's leader whenever a new leader is
elected, and it is required for enabling cascading replication from the secondary sites.

Be sure to use [password credentials](../../postgresql/replication_and_failover.md#database-authorization-for-patroni)
and other database best practices.

##### Step 1. Configure Patroni permanent replication slot on the primary site

To set up database replication with Patroni on a secondary node, we need to
configure a _permanent replication slot_ on the primary node's Patroni cluster,
and ensure password authentication is used.

For each Patroni instance on the primary site **starting on the Patroni
Leader instance**:

1. SSH into your Patroni instance and login as root:

   ```shell
   sudo -i
   ```

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

   ```ruby
   roles(['patroni_role'])

   consul['services'] = %w(postgresql)
   consul['configuration'] = {
     retry_join: %w[CONSUL_PRIMARY1_IP CONSUL_PRIMARY2_IP CONSUL_PRIMARY3_IP]
   }

   # You need one entry for each secondary, with a unique name following PostgreSQL slot_name constraints:
   #
   # Configuration syntax is: 'unique_slotname' => { 'type' => 'physical' },
   # We don't support setting a permanent replication slot for logical replication type
   patroni['replication_slots'] = {
     'geo_secondary' => { 'type' => 'physical' }
   }

   patroni['use_pg_rewind'] = true
   patroni['postgresql']['max_wal_senders'] = 8 # Use double of the amount of patroni/reserved slots (3 patronis + 1 reserved slot for a Geo secondary).
   patroni['postgresql']['max_replication_slots'] = 8 # Use double of the amount of patroni/reserved slots (3 patronis + 1 reserved slot for a Geo secondary).
   patroni['username'] = 'PATRONI_API_USERNAME'
   patroni['password'] = 'PATRONI_API_PASSWORD'
   patroni['replication_password'] = 'PLAIN_TEXT_POSTGRESQL_REPLICATION_PASSWORD'

   # Add all patroni nodes to the allowlist
   patroni['allowlist'] = %w[
     127.0.0.1/32
     PATRONI_PRIMARY1_IP/32 PATRONI_PRIMARY2_IP/32 PATRONI_PRIMARY3_IP/32
     PATRONI_SECONDARY1_IP/32 PATRONI_SECONDARY2_IP/32 PATRONI_SECONDARY3_IP/32
   ]

   # We list all secondary instances as they can all become a Standby Leader
   postgresql['md5_auth_cidr_addresses'] = %w[
     PATRONI_PRIMARY1_IP/32 PATRONI_PRIMARY2_IP/32 PATRONI_PRIMARY3_IP/32 PATRONI_PRIMARY_PGBOUNCER/32
     PATRONI_SECONDARY1_IP/32 PATRONI_SECONDARY2_IP/32 PATRONI_SECONDARY3_IP/32 PATRONI_SECONDARY_PGBOUNCER/32
   ]

   postgresql['pgbouncer_user_password'] = 'PGBOUNCER_PASSWORD_HASH'
   postgresql['sql_replication_password'] = 'POSTGRESQL_REPLICATION_PASSWORD_HASH'
   postgresql['sql_user_password'] = 'POSTGRESQL_PASSWORD_HASH'
   postgresql['listen_address'] = '0.0.0.0' # You can use a public or VPC address here instead
   ```

1. Reconfigure GitLab for the changes to take effect:

   ```shell
   gitlab-ctl reconfigure
   ```

##### Step 2. Configure the internal load balancer on the primary site

To avoid reconfiguring the Standby Leader on the secondary site whenever a new
Leader is elected on the primary site, we need to set up a TCP internal load
balancer which gives a single endpoint for connecting to the Patroni
cluster's Leader.

The Omnibus GitLab packages do not include a Load Balancer. Here's how you
could do it with [HAProxy](https://www.haproxy.org/).

The following IPs and names are used as an example:

- `10.6.0.21`: Patroni 1 (`patroni1.internal`)
- `10.6.0.22`: Patroni 2 (`patroni2.internal`)
- `10.6.0.23`: Patroni 3 (`patroni3.internal`)

```plaintext
global
    log /dev/log local0
    log localhost local1 notice
    log stdout format raw local0

defaults
    log global
    default-server inter 3s fall 3 rise 2 on-marked-down shutdown-sessions

frontend internal-postgresql-tcp-in
    bind *:5000
    mode tcp
    option tcplog

    default_backend postgresql

backend postgresql
    option httpchk
    http-check expect status 200

    server patroni1.internal 10.6.0.21:5432 maxconn 100 check port 8008
    server patroni2.internal 10.6.0.22:5432 maxconn 100 check port 8008
    server patroni3.internal 10.6.0.23:5432 maxconn 100 check port 8008
```

Refer to your preferred Load Balancer's documentation for further guidance.

##### Step 3. Configure a PgBouncer node on the secondary site

A production-ready and highly available configuration requires at least
three Consul nodes, a minimum of one PgBouncer node, but it's recommended to have
one per database node. An internal load balancer (TCP) is required when there is
more than one PgBouncer service nodes. The internal load balancer provides a single
endpoint for connecting to the PgBouncer cluster. For more information,
see [High Availability with Omnibus GitLab](../../postgresql/replication_and_failover.md).

Follow the minimal configuration for the PgBouncer node:

1. SSH into your PgBouncer node and login as root:

   ```shell
   sudo -i
   ```

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

   ```ruby
   # Disable all components except Pgbouncer and Consul agent
   roles(['pgbouncer_role'])

   # PgBouncer configuration
   pgbouncer['admin_users'] = %w(pgbouncer gitlab-consul)
   pgbouncer['users'] = {
   'gitlab-consul': {
      # Generate it with: `gitlab-ctl pg-password-md5 gitlab-consul`
      password: 'GITLAB_CONSUL_PASSWORD_HASH'
    },
     'pgbouncer': {
       # Generate it with: `gitlab-ctl pg-password-md5 pgbouncer`
       password: 'PGBOUNCER_PASSWORD_HASH'
     }
   }

   # Consul configuration
   consul['watchers'] = %w(postgresql)
   consul['configuration'] = {
     retry_join: %w[CONSUL_SECONDARY1_IP CONSUL_SECONDARY2_IP CONSUL_SECONDARY3_IP]
   }
   consul['monitoring_service_discovery'] =  true
   ```

1. Reconfigure GitLab for the changes to take effect:

   ```shell
   gitlab-ctl reconfigure
   ```

1. Create a `.pgpass` file so Consul is able to reload PgBouncer. Enter the `PLAIN_TEXT_PGBOUNCER_PASSWORD` twice when asked:

   ```shell
   gitlab-ctl write-pgpass --host 127.0.0.1 --database pgbouncer --user pgbouncer --hostuser gitlab-consul
   ```

1. Reload the PgBouncer service:

   ```shell
   gitlab-ctl hup pgbouncer
   ```

##### Step 4. Configure a Standby cluster on the secondary site

NOTE:
If you are converting a secondary site to a Patroni Cluster, you must start
on the PostgreSQL instance. It becomes the Patroni Standby Leader instance,
and then you can switchover to another replica if you need.

For each Patroni instance on the secondary site:

1. SSH into your Patroni node and login as root:

   ```shell
   sudo -i
   ```

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

   ```ruby
   roles(['consul_role', 'patroni_role'])

   consul['enable'] = true
   consul['configuration'] = {
     retry_join: %w[CONSUL_SECONDARY1_IP CONSUL_SECONDARY2_IP CONSUL_SECONDARY3_IP]
   }

   postgresql['md5_auth_cidr_addresses'] = [
     'PATRONI_SECONDARY1_IP/32', 'PATRONI_SECONDARY2_IP/32', 'PATRONI_SECONDARY3_IP/32', 'PATRONI_SECONDARY_PGBOUNCER/32',
     # Any other instance that needs access to the database as per documentation
   ]


   # Add patroni nodes to the allowlist
   patroni['allowlist'] = %w[
     127.0.0.1/32
     PATRONI_SECONDARY1_IP/32 PATRONI_SECONDARY2_IP/32 PATRONI_SECONDARY3_IP/32
   ]

   patroni['standby_cluster']['enable'] = true
   patroni['standby_cluster']['host'] = 'INTERNAL_LOAD_BALANCER_PRIMARY_IP'
   patroni['standby_cluster']['port'] = INTERNAL_LOAD_BALANCER_PRIMARY_PORT
   patroni['standby_cluster']['primary_slot_name'] = 'geo_secondary' # Or the unique replication slot name you setup before
   patroni['username'] = 'PATRONI_API_USERNAME'
   patroni['password'] = 'PATRONI_API_PASSWORD'
   patroni['replication_password'] = 'PLAIN_TEXT_POSTGRESQL_REPLICATION_PASSWORD'
   patroni['use_pg_rewind'] = true
   patroni['postgresql']['max_wal_senders'] = 5 # A minimum of three for one replica, plus two for each additional replica
   patroni['postgresql']['max_replication_slots'] = 5 # A minimum of three for one replica, plus two for each additional replica

   postgresql['pgbouncer_user_password'] = 'PGBOUNCER_PASSWORD_HASH'
   postgresql['sql_replication_password'] = 'POSTGRESQL_REPLICATION_PASSWORD_HASH'
   postgresql['sql_user_password'] = 'POSTGRESQL_PASSWORD_HASH'
   postgresql['listen_address'] = '0.0.0.0' # You can use a public or VPC address here instead

   gitlab_rails['dbpassword'] = 'POSTGRESQL_PASSWORD'
   gitlab_rails['enable'] = true
   gitlab_rails['auto_migrate'] = false
   ```

1. Reconfigure GitLab for the changes to take effect.
   This is required to bootstrap PostgreSQL users and settings.

   - If this is a fresh installation of Patroni:

     ```shell
     gitlab-ctl reconfigure
     ```

   - If you are configuring a Patroni standby cluster on a site that previously had a working Patroni cluster:

     ```shell
     gitlab-ctl stop patroni
     rm -rf /var/opt/gitlab/postgresql/data
     /opt/gitlab/embedded/bin/patronictl -c /var/opt/gitlab/patroni/patroni.yaml remove postgresql-ha
     gitlab-ctl reconfigure
     gitlab-ctl start patroni
     ```

### Migrating from repmgr to Patroni

1. Before migrating, it is recommended that there is no replication lag between the primary and secondary sites and that replication is paused. In GitLab 13.2 and later, you can pause and resume replication with `gitlab-ctl geo-replication-pause` and `gitlab-ctl geo-replication-resume` on a Geo secondary database node.
1. Follow the [instructions to migrate repmgr to Patroni](../../postgresql/replication_and_failover.md#switching-from-repmgr-to-patroni). When configuring Patroni on each primary site database node, add `patroni['replication_slots'] = { '<slot_name>' => 'physical' }`
to `gitlab.rb` where `<slot_name>` is the name of the replication slot for your Geo secondary. This ensures that Patroni recognizes the replication slot as permanent and not drop it upon restarting.
1. If database replication to the secondary was paused before migration, resume replication once Patroni is confirmed working on the primary.

### Migrating a single PostgreSQL node to Patroni

Before the introduction of Patroni, Geo had no Omnibus support for HA setups on the secondary node.

With Patroni it's now possible to support that. In order to migrate the existing PostgreSQL to Patroni:

1. Make sure you have a Consul cluster setup on the secondary (similar to how you set it up on the primary).
1. [Configure a permanent replication slot](#step-1-configure-patroni-permanent-replication-slot-on-the-primary-site).
1. [Configure the internal load balancer](#step-2-configure-the-internal-load-balancer-on-the-primary-site).
1. [Configure a PgBouncer node](#step-3-configure-a-pgbouncer-node-on-the-secondary-site)
1. [Configure a Standby Cluster](#step-4-configure-a-standby-cluster-on-the-secondary-site)
   on that single node machine.

You end up with a "Standby Cluster" with a single node. That allows you to later on add additional Patroni nodes
by following the same instructions above.

### Configuring Patroni cluster for the tracking PostgreSQL database

Secondary sites 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 in a highly available configuration, don't use the `geo_secondary_role` above.
Instead, follow the instructions below.

A production-ready and secure setup requires at least three Consul nodes, two
Patroni nodes and one PgBouncer node on the secondary site.

Because of [omnibus-6587](https://gitlab.com/gitlab-org/omnibus-gitlab/-/issues/6587), Consul can't track multiple
services, so these need to be different than the nodes used for the Standby Cluster database.

Be sure to use [password credentials](../../postgresql/replication_and_failover.md#database-authorization-for-patroni)
and other database best practices.

#### Step 1. Configure a PgBouncer node on the secondary site

Follow the minimal configuration for the PgBouncer node for the tracking database:

1. SSH into your PgBouncer node and login as root:

   ```shell
   sudo -i
   ```

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

   ```ruby
   # Disable all components except Pgbouncer and Consul agent
   roles(['pgbouncer_role'])

   # PgBouncer configuration
   pgbouncer['users'] = {
     'pgbouncer': {
       password: 'PGBOUNCER_PASSWORD_HASH'
     }
   }

   pgbouncer['databases'] = {
     gitlabhq_geo_production: {
       user: 'pgbouncer',
       password: 'PGBOUNCER_PASSWORD_HASH'
     }
   }

   # Consul configuration
   consul['watchers'] = %w(postgresql)

   consul['configuration'] = {
     retry_join: %w[CONSUL_TRACKINGDB1_IP CONSUL_TRACKINGDB2_IP CONSUL_TRACKINGDB3_IP]
   }

   consul['monitoring_service_discovery'] =  true

   # GitLab database settings
   gitlab_rails['db_database'] = 'gitlabhq_geo_production'
   gitlab_rails['db_username'] = 'gitlab_geo'
   ```

1. Reconfigure GitLab for the changes to take effect:

   ```shell
   gitlab-ctl reconfigure
   ```

1. Create a `.pgpass` file so Consul is able to reload PgBouncer. Enter the `PLAIN_TEXT_PGBOUNCER_PASSWORD` twice when asked:

   ```shell
   gitlab-ctl write-pgpass --host 127.0.0.1 --database pgbouncer --user pgbouncer --hostuser gitlab-consul
   ```

1. Restart the PgBouncer service:

   ```shell
   gitlab-ctl restart pgbouncer
   ```

#### Step 2. Configure a Patroni cluster

For each Patroni instance on the secondary site for the tracking database:

1. SSH into your Patroni node and login as root:

   ```shell
   sudo -i
   ```

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

   ```ruby
   # Disable all components except PostgreSQL, Patroni, and Consul
   roles(['patroni_role'])

   # Consul configuration
   consul['services'] = %w(postgresql)

   consul['configuration'] = {
     server: true,
     retry_join: %w[CONSUL_TRACKINGDB1_IP CONSUL_TRACKINGDB2_IP CONSUL_TRACKINGDB3_IP]
   }

   # PostgreSQL configuration
   postgresql['listen_address'] = '0.0.0.0'
   postgresql['hot_standby'] = 'on'
   postgresql['wal_level'] = 'replica'

   postgresql['pgbouncer_user_password'] = 'PGBOUNCER_PASSWORD_HASH'
   postgresql['sql_replication_password'] = 'POSTGRESQL_REPLICATION_PASSWORD_HASH'
   postgresql['sql_user_password'] = 'POSTGRESQL_PASSWORD_HASH'

   postgresql['md5_auth_cidr_addresses'] = [
      'PATRONI_TRACKINGDB1_IP/32', 'PATRONI_TRACKINGDB2_IP/32', 'PATRONI_TRACKINGDB3_IP/32', 'PATRONI_TRACKINGDB_PGBOUNCER/32',
      # Any other instance that needs access to the database as per documentation
   ]

   # Add patroni nodes to the allowlist
   patroni['allowlist'] = %w[
     127.0.0.1/32
     PATRONI_TRACKINGDB1_IP/32 PATRONI_TRACKINGDB2_IP/32 PATRONI_TRACKINGDB3_IP/32
   ]

   # Patroni configuration
   patroni['username'] = 'PATRONI_API_USERNAME'
   patroni['password'] = 'PATRONI_API_PASSWORD'
   patroni['replication_password'] = 'PLAIN_TEXT_POSTGRESQL_REPLICATION_PASSWORD'
   patroni['postgresql']['max_wal_senders'] = 5 # A minimum of three for one replica, plus two for each additional replica

   # GitLab database settings
   gitlab_rails['db_database'] = 'gitlabhq_geo_production'
   gitlab_rails['db_username'] = 'gitlab_geo'
   gitlab_rails['enable'] = true

   # Disable automatic database migrations
   gitlab_rails['auto_migrate'] = false
   ```

1. Reconfigure GitLab for the changes to take effect.
   This is required to bootstrap PostgreSQL users and settings:

   ```shell
   gitlab-ctl reconfigure
   ```

#### Step 3. Configure the tracking database on the secondary nodes

For each node running the `gitlab-rails`, `sidekiq`, and `geo-logcursor` services:

1. SSH into your node and login as root:

   ```shell
   sudo -i
   ```

1. Edit `/etc/gitlab/gitlab.rb` and add the following attributes. You may have other attributes set, but the following need to be set.

   ```ruby
   # Tracking database settings
   geo_secondary['db_username'] = 'gitlab_geo'
   geo_secondary['db_password'] = 'PLAIN_TEXT_PGBOUNCER_PASSWORD'
   geo_secondary['db_database'] = 'gitlabhq_geo_production'
   geo_secondary['db_host'] = 'PATRONI_TRACKINGDB_PGBOUNCER_IP'
   geo_secondary['db_port'] = 6432
   geo_secondary['auto_migrate'] = false

   # Disable the tracking database service
   geo_postgresql['enable'] = false
   ```

1. Reconfigure GitLab for the changes to take effect.

   ```shell
   gitlab-ctl reconfigure
   ```

1. Run the tracking database migrations:

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

### Migrating a single tracking database node to Patroni

Before the introduction of Patroni, Geo had no Omnibus support for HA setups on
the secondary node.

With Patroni, it's now possible to support that. Due to some restrictions on the
Patroni implementation on Omnibus that do not allow us to manage two different
clusters on the same machine, we recommend setting up a new Patroni cluster for
the tracking database by following the same instructions above.

The secondary nodes backfill the new tracking database, and no data
synchronization is required.

## Troubleshooting

Read the [troubleshooting document](../replication/troubleshooting.md).
