debian-mirror-gitlab/doc/administration/geo/replication/database_source.md

# Geo database replication (source) **[PREMIUM ONLY]**

NOTE: **Note:**
This documentation applies to GitLab source installations. In GitLab 11.5, this documentation was deprecated and will be removed in a future release.
Please consider [migrating to GitLab Omnibus install](https://docs.gitlab.com/omnibus/update/convert_to_omnibus.html). For installations
using the Omnibus GitLab packages, follow the
[**database replication for Omnibus GitLab**][database] guide.

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](index.md#using-gitlab-installed-from-source-deprecated).

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
**primary** database server, and the **secondary** ones which are read-only will
connect to **secondary** database servers (which are read-only too).

NOTE: **Note:**
In many databases' documentation, you will 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 the **primary** node retains all the data necessary for the secondaries to
recover. See below for more details.

The following guide assumes that:

- You are using PostgreSQL 9.6 or later which includes the
  [`pg_basebackup` tool][pgback] and improved [Foreign Data Wrapper][FDW] support.
- You have a **primary** node already set up (the GitLab server you are
  replicating from), running PostgreSQL 9.6 or later, and
  you have a new **secondary** server set up with the same versions of the OS,
  PostgreSQL, and GitLab on all nodes.
- The IP of the **primary** server for our examples is `198.51.100.1`, whereas the
  **secondary** node's IP is `198.51.100.2`. Note that the **primary** and **secondary** servers
  **must** be able to communicate over these addresses. These IP addresses can either
  be public or private.
  
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-ee/issues/7420).

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

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

    ```sh
    sudo -i
    ```

1. Add this node as the Geo **primary** by running:

    ```sh
    bundle exec rake geo:set_primary_node
    ```

1. Create a [replication user] named `gitlab_replicator`:

    ```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. Make sure your the `gitlab` database user has a password defined:

    ```sh
    sudo \
       -u postgres psql \
       -d template1 \
       -c "ALTER USER gitlab WITH ENCRYPTED PASSWORD '<database_password>';"
    ```

1. Edit the content of `database.yml` in `production:` and add the password like the example below:

    ```yaml
    #
    # PRODUCTION
    #
    production:
      adapter: postgresql
      encoding: unicode
      database: gitlabhq_production
      pool: 10
      username: gitlab
      password: <database_password>
      host: /var/opt/gitlab/geo-postgresql
    ```

1. Set up TLS support for the PostgreSQL **primary** server:

    CAUTION: **Warning**:
    Only skip this step if you **know** that PostgreSQL traffic
    between the **primary** and **secondary** nodes will be secured through some other
    means, e.g., a known-safe physical network path or a site-to-site VPN that
    you have configured.

    If you are replicating your database across the open Internet, it is
    **essential** that the connection is TLS-secured. Correctly configured, this
    provides protection against both passive eavesdroppers and active
    "man-in-the-middle" attackers.

    To generate a self-signed certificate and key, run this command:

    ```sh
    openssl req \
       -nodes \
       -batch \
       -x509 \
       -newkey rsa:4096 \
       -keyout server.key \
       -out server.crt \
       -days 3650
    ```

    This will create two files - `server.key` and `server.crt` - that you can
    use for authentication.

    Copy them to the correct location for your PostgreSQL installation:

    ```sh
    # Copying a self-signed certificate and key
    install -o postgres -g postgres -m 0400 -T server.crt ~postgres/9.x/main/data/server.crt
    install -o postgres -g postgres -m 0400 -T server.key ~postgres/9.x/main/data/server.key
    ```

    Add this configuration to `postgresql.conf`, removing any existing
    configuration for `ssl_cert_file` or `ssl_key_file`:

    ```
    ssl = on
    ssl_cert_file='server.crt'
    ssl_key_file='server.key'
    ```

1. Edit `postgresql.conf` to configure the **primary** server for streaming replication
   (for Debian/Ubuntu that would be `/etc/postgresql/9.x/main/postgresql.conf`):

    ```
    listen_address = '<primary_node_ip>'
    wal_level = hot_standby
    max_wal_senders = 5
    min_wal_size = 80MB
    max_wal_size = 1GB
    max_replicaton_slots = 1 # Number of Geo secondary nodes
    wal_keep_segments = 10
    hot_standby = on
    ```

    NOTE: **Note**:
    Be sure to set `max_replication_slots` to the number of Geo **secondary**
    nodes that you may potentially have (at least 1).

    For security reasons, PostgreSQL by default only listens on the local
    interface (e.g. 127.0.0.1). However, Geo needs to communicate
    between the **primary** and **secondary** nodes over a common network, such as a
    corporate LAN or the public Internet. For this reason, we need to
    configure PostgreSQL to listen on more interfaces.

    The `listen_address` option opens PostgreSQL up to external connections
    with the interface corresponding to the given IP. See [the PostgreSQL
    documentation][pg-docs-runtime-conn] for more details.

    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][pg-docs-runtime-replication] for more information.

1. Set the access control on the **primary** node to allow TCP connections using the
   server's public IP and set the connection from the **secondary** node to require a
   password. Edit `pg_hba.conf` (for Debian/Ubuntu that would be
   `/etc/postgresql/9.x/main/pg_hba.conf`):

    ```sh
    host    all             all                      <primary_node_ip>/32      md5
    host    replication     gitlab_replicator        <secondary_node_ip>/32      md5
    ```

    If you want to add another secondary, add one more row like the replication 
    one and change the IP address:

    ```sh
    host    all             all                      <primary_node_ip>/32      md5
    host    replication     gitlab_replicator        <secondary_node_ip>/32      md5
    host    replication     gitlab_replicator        <another_secondary_node_ip>/32  md5
    ```

1. Restart PostgreSQL for the changes to take effect.

1. Choose a database-friendly name to use for your secondary 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.

1. Create the replication slot on the **primary** node:

    ```sh
    $ sudo -u postgres psql -c "SELECT * FROM pg_create_physical_replication_slot('secondary_example');"
      slot_name         | xlog_position
      ------------------+---------------
      secondary_example |
      (1 row)
    ```

1. Now that the PostgreSQL server is set up to accept remote connections, run
   `netstat -plnt` to make sure that PostgreSQL is listening to the server's
   public IP.

### Step 2. Configure the secondary server

Follow the first steps in ["configure the secondary server"][database-replication] and note that since you are installing from source, the username and
group listed as `gitlab-psql` in those steps should be replaced by `postgres`
instead. After completing the "Test that the `gitlab-psql` user can connect to
the **primary** node's database" step, continue here:

1. Edit `postgresql.conf` to configure the secondary for streaming replication
   (for Debian/Ubuntu that would be `/etc/postgresql/9.*/main/postgresql.conf`):

    ```sh
    wal_level = hot_standby
    max_wal_senders = 5
    checkpoint_segments = 10
    wal_keep_segments = 10
    hot_standby = on
    ```

1. Restart PostgreSQL for the changes to take effect.

#### Enable tracking database on the secondary server

Geo secondary nodes use a tracking database to keep track of replication status
and recover automatically from some replication issues. Follow the steps below to create
the tracking database.

1. On the secondary node, run the following command to create `database_geo.yml` with the
   information of your secondary PostgreSQL instance:

    ```sh
    sudo cp /home/git/gitlab/config/database_geo.yml.postgresql /home/git/gitlab/config/database_geo.yml
    ```

1. Edit the content of `database_geo.yml` in `production:` as in the example below:

    ```yaml
    #
    # PRODUCTION
    #
    production:
      adapter: postgresql
      encoding: unicode
      database: gitlabhq_geo_production
      pool: 10
      username: gitlab_geo
      # password:
      host: /var/opt/gitlab/geo-postgresql
    ```

1. Create the database `gitlabhq_geo_production` on the PostgreSQL instance of the **secondary** node.

1. Set up the Geo tracking database:

    ```sh
    bundle exec rake geo:db:migrate
    ```

1. Configure the [PostgreSQL FDW][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.

    ```sh
    #!/bin/bash

    # Secondary Database connection params:
    DB_HOST="/var/opt/gitlab/postgresql" # change to the public IP or VPC private IP if its an external server
    DB_NAME="gitlabhq_production"
    DB_USER="gitlab"
    DB_PORT="5432"

    # Tracking Database connection params:
    GEO_DB_HOST="/var/opt/gitlab/geo-postgresql" # change to the public IP or VPC private IP if its an external server
    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}');"
    query_exec "CREATE SCHEMA gitlab_secondary;"
    query_exec "GRANT USAGE ON FOREIGN SERVER gitlab_secondary TO ${GEO_DB_USER};"
    ```

    And edit the content of `database_geo.yml` and to add `fdw: true` to
    the  `production:` block.

### 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 for Debian/Ubuntu. 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:

    ```sh
    sudo -i
    ```

1. Save the snippet below in a file, let's say `/tmp/replica.sh`. Modify the
   embedded paths if necessary:

    ```
    #!/bin/bash

    PORT="5432"
    USER="gitlab_replicator"
    echo ---------------------------------------------------------------
    echo WARNING: Make sure this script is run from the secondary server
    echo ---------------------------------------------------------------
    echo
    echo Enter the IP or FQDN of the primary PostgreSQL server
    read HOST
    echo Enter the password for $USER@$HOST
    read -s PASSWORD
    echo Enter the required sslmode
    read SSLMODE

    echo Stopping PostgreSQL and all GitLab services
    sudo service gitlab stop
    sudo service postgresql stop

    echo Backing up postgresql.conf
    sudo -u postgres mv /var/opt/gitlab/postgresql/data/postgresql.conf /var/opt/gitlab/postgresql/

    echo Cleaning up old cluster directory
    sudo -u postgres rm -rf /var/opt/gitlab/postgresql/data

    echo Starting base backup as the replicator user
    echo Enter the password for $USER@$HOST
    sudo -u postgres /opt/gitlab/embedded/bin/pg_basebackup -h $HOST -D /var/opt/gitlab/postgresql/data -U gitlab_replicator -v -x -P

    echo Writing recovery.conf file
    sudo -u postgres bash -c "cat > /var/opt/gitlab/postgresql/data/recovery.conf <<- _EOF1_
      standby_mode = 'on'
      primary_conninfo = 'host=$HOST port=$PORT user=$USER password=$PASSWORD sslmode=$SSLMODE'
    _EOF1_
    "

    echo Restoring postgresql.conf
    sudo -u postgres mv /var/opt/gitlab/postgresql/postgresql.conf /var/opt/gitlab/postgresql/data/

    echo Starting PostgreSQL
    sudo service postgresql start
    ```

1. Run it with:

    ```sh
    bash /tmp/replica.sh
    ```

    When prompted, enter the IP/FQDN of the **primary** node, and the password you set up
    for the `gitlab_replicator` user in the first step.

    You should use `verify-ca` for the `sslmode`. You can use `disable` if you
    are happy 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][pg-docs-ssl];
    the instructions above are carefully written to ensure protection against
    both passive eavesdroppers and active "man-in-the-middle" attackers.

The replication process is now over.

## PGBouncer support (optional)

1. First, enter the PostgreSQL console as an admin user.

1. Then create the read-only user:

    ```sql
    -- NOTE: Use the password defined earlier
    CREATE USER gitlab_geo_fdw WITH password '<your_password_here>';
    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. Enter the PostgreSQL console on the **secondary** tracking database and change the user mapping to this new user:

    ```
    ALTER USER MAPPING FOR gitlab_geo SERVER gitlab_secondary OPTIONS (SET user 'gitlab_geo_fdw')
    ```

## MySQL replication

MySQL replication is not supported for Geo.

## Troubleshooting

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

[replication-slots-article]: https://medium.com/@tk512/replication-slots-in-postgresql-b4b03d277c75
[pgback]: http://www.postgresql.org/docs/9.6/static/app-pgbasebackup.html
[replication user]:https://wiki.postgresql.org/wiki/Streaming_Replication
[FDW]: https://www.postgresql.org/docs/9.6/static/postgres-fdw.html
[database]: database.md
[add-geo-node]: configuration.md#step-3-add-the-secondary-gitlab-node
[database-replication]: database.md#step-2-configure-the-secondary-server
[pg-docs-ssl]: https://www.postgresql.org/docs/9.6/static/libpq-ssl.html#LIBPQ-SSL-PROTECTION
[pg-docs-runtime-conn]: https://www.postgresql.org/docs/9.6/static/runtime-config-connection.html
[pg-docs-runtime-replication]: https://www.postgresql.org/docs/9.6/static/runtime-config-replication.html