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

NOTE: **Note:**
If your GitLab installation uses external (not managed by Omnibus) PostgreSQL
instances, the Omnibus roles will not be able to perform all necessary
configuration steps. In this case,
[follow the Geo with external PostgreSQL instances document instead](external_database.md).

NOTE: **Note:**
The stages of the setup process must be completed in the documented order.
Before attempting the steps in this stage, [complete all prior stages][toc].

This document describes the minimal steps you have to take in order to
replicate your **primary** GitLab database to a **secondary** node's database. You may
have to change some values according to your database setup, how big it is, etc.

You are encouraged to first read through all the steps before executing them
in your testing/production environment.

## PostgreSQL replication

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

NOTE: **Note:**
In database documentation, you may see "**primary**" being referenced as "master"
and "**secondary**" as either "slave" or "standby" server (read-only).

We recommend using [PostgreSQL replication slots][replication-slots-article]
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 9.6 or later
  which includes the [`pg_basebackup` tool](https://www.postgresql.org/docs/9.6/app-pgbasebackup.html) and improved
  [Foreign Data Wrapper](https://www.postgresql.org/docs/9.6/postgres-fdw.html) support.
- 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.

CAUTION: **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 node:

   ```ruby
   # The unique identifier for the Geo node.
   gitlab_rails['geo_node_name'] = '<node_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 will use your defined `external_url` in `/etc/gitlab/gitlab.rb`.

1. GitLab 10.4 and up only: Do the following to make sure the `gitlab` database user has a password defined:

   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 Unicorn 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. Omnibus GitLab already has a [replication user]
   called `gitlab_replicator`. You must set the password for this user manually.
   You will be prompted to enter a password:

   ```shell
   gitlab-ctl set-replication-password
   ```

   This command will also read the `postgresql['sql_replication_user']` Omnibus
   setting in case you have changed `gitlab_replicator` username to something
   else.

   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: **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 will be 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/9.6/runtime-config-connection.html)
   for more details.

   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
   ## - configure dependent flags automatically to enable Geo
   ##
   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/9.6/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
   will be 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
   will 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 unicorn
   gitlab-ctl stop sidekiq
   ```

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

1. [Check TCP connectivity][rake-maintenance] to the **primary** node's PostgreSQL server:

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

   NOTE: **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 will now only recognize 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 to enable FDW support:

   This step is similar to how we configured the **primary** instance.
   We need to enable this, to enable FDW support, 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_user_password'] = '<md5_hash_of_your_password>'
   gitlab_rails['db_password'] = '<your_password_here>'

   ##
   ## Enable FDW support for the Geo Tracking Database (improves performance)
   ##
   geo_secondary['db_fdw'] = true
   ```

   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 and reconfigure again:

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

   This last reconfigure will provision the FDW configuration and enable it.

### 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.

CAUTION: **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

   CAUTION: **Warning:** Each Geo **secondary** node must have its own unique replication slot name.
   Using the same slot name between two secondaries will break PostgreSQL replication.

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

   NOTE: **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 will need
     to increase the timeout, e.g., `--backup-timeout=3600` if you expect the
     initial replication to take under an hour.
   - Pass `--sslmode=disable` to skip PostgreSQL TLS authentication altogether
     (e.g., 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/9.6/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 will attempt to create the
     replication slot automatically if it does not exist.
   - If you're repurposing an old server into a Geo **secondary** node, you'll 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. We recommend using PgBouncer if you use GitLab in a
high-availability configuration with a cluster of nodes supporting a Geo
**primary** node and another cluster of nodes supporting a Geo **secondary** node. For more
information, see [High Availability with GitLab Omnibus](../../high_availability/database.md#high-availability-with-gitlab-omnibus-premium-only).

For a Geo **secondary** node to work properly with PgBouncer in front of the database,
it will need a separate read-only user to make [PostgreSQL FDW queries](https://www.postgresql.org/docs/9.6/postgres-fdw.html)
work:

1. On the **primary** Geo database, enter the PostgreSQL on the console as an
   admin user. If you are using an Omnibus-managed database, log onto the **primary**
   node that is running the PostgreSQL database (the default Omnibus database name is gitlabhq_production):

   ```shell
    sudo \
       -u gitlab-psql /opt/gitlab/embedded/bin/psql \
       -h /var/opt/gitlab/postgresql gitlabhq_production
   ```

1. Then create the read-only user:

   ```sql
   -- NOTE: Use the password defined earlier
   CREATE USER gitlab_geo_fdw WITH password 'mypassword';
   GRANT CONNECT ON DATABASE gitlabhq_production to gitlab_geo_fdw;
   GRANT USAGE ON SCHEMA public TO gitlab_geo_fdw;
   GRANT SELECT ON ALL TABLES IN SCHEMA public TO gitlab_geo_fdw;
   GRANT SELECT ON ALL SEQUENCES IN SCHEMA public TO gitlab_geo_fdw;

   -- Tables created by "gitlab" should be made read-only for "gitlab_geo_fdw"
   -- automatically.
   ALTER DEFAULT PRIVILEGES FOR USER gitlab IN SCHEMA public GRANT SELECT ON TABLES TO gitlab_geo_fdw;
   ALTER DEFAULT PRIVILEGES FOR USER gitlab IN SCHEMA public GRANT SELECT ON SEQUENCES TO gitlab_geo_fdw;
   ```

1. On the **secondary** nodes, change `/etc/gitlab/gitlab.rb`:

   ```
   geo_postgresql['fdw_external_user'] = 'gitlab_geo_fdw'
   ```

1. Save the file and reconfigure GitLab for the changes to be applied:

   ```shell
   gitlab-ctl reconfigure
   ```

## Troubleshooting

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

[replication-slots-article]: https://medium.com/@tk512/replication-slots-in-postgresql-b4b03d277c75
[replication user]:https://wiki.postgresql.org/wiki/Streaming_Replication
[toc]: index.md#using-omnibus-gitlab
[rake-maintenance]: ../../raketasks/maintenance.md
