# Setting up MariaDB MaxScale

This document is designed as a quick introduction to setting up MariaDB MaxScale
in an environment in which you have either a MariaDB Master-Slave replication cluster
with one master and multiple slave servers or a multi-node Galera cluster.
The process of setting and configuring MariaDB MaxScale will be covered within this document.

The installation and configuration of the MariaDB Replication or the Galera cluster
will not be covered nor will any discussion of installation management tools
to handle automated or semi-automated failover of the replication cluster.
The [Setting Up Replication](https://mariadb.com/kb/en/mariadb/setting-up-replication/)
article on the MariaDB knowledgebase can help you get started with replication clusters
and the [Getting Started With Mariadb Galera Cluster](https://mariadb.com/kb/en/mariadb/getting-started-with-mariadb-galera-cluster/) article will help you set up a Galera cluster.

This tutorial will assume the user is running from one of the binary distributions
available and has installed this in the default location.
Building from source code in GitHub is covered in the
[Building from Source](../Getting-Started/Building-MaxScale-from-Source-Code.md) document.

## Process

The steps involved in setting up MariaDB MaxScale are:

* Install the package relevant to your distribution

* Create the required users in your MariaDB or MySQL Replication cluster

* Create a MariaDB MaxScale configuration file

## Installation

The precise installation process will vary from one distribution to another
details of what to do with the RPM and DEB packages can be found on the download
site when you select the distribution you are downloading from.
The process involves setting up your package manager to include the MariaDB repositories
and then running the package manager for your distribution (usually yum or apt-get).

Upon successful completion of the installation command you will have MariaDB MaxScale
installed and ready to be run but without a configuration.
You must create a configuration file before you first run MariaDB MaxScale
which is covered in a later section.

## Creating Database Users

MariaDB MaxScale needs to connect to the backend databases and run queries for
two reasons; one to determine the current state of the database and the other to
retrieve the user information for the database cluster. The first pair of
credentials will be used by the monitor modules and the second is used by
MariaDB MaxScale itself. This may be done either using two separate usernames
or with a single user.

The first user required must be able to select data from the table mysql.user,
to create this user follow the steps below.

1. Connect to the current master server in your replication tree as the root user

2. Create the user, substituting the username, password and host on which maxscale
runs within your environment
```
MariaDB [(none)]> create user '*username*'@'*maxscalehost*' identified by '*password*';

**Query OK, 0 rows affected (0.00 sec)**
```
3. Grant select privileges on the mysql.user table.
```
MariaDB [(none)]> grant SELECT on mysql.user to '*username*'@'*maxscalehost*';

**Query OK, 0 rows affected (0.03 sec)**
```
Additionally, `SELECT` privileges on the `mysql.db` and `mysql.tables_priv` tables
and `SHOW DATABASES` privileges are required in order to load databases name
and grants suitable for database name authorization.
```
MariaDB [(none)]> GRANT SELECT ON mysql.db TO 'username'@'maxscalehost';

**Query OK, 0 rows affected (0.00 sec)**

MariaDB [(none)]> GRANT SELECT ON mysql.tables_priv TO 'username'@'maxscalehost';

**Query OK, 0 rows affected (0.00 sec)**

MariaDB [(none)]> GRANT SHOW DATABASES ON *.* TO 'username'@'maxscalehost';

**Query OK, 0 rows affected (0.00 sec)**
```
The second user is used to monitored the state of the cluster. This user, which may be
the same username as the first, requires permissions to access the various sources
of monitoring data. In order to monitor a replication cluster this user must be granted
the role REPLICATION CLIENT. This is only required by the MySQL monitor
and Multi-Master monitor modules.

```
MariaDB [(none)]> grant REPLICATION CLIENT on *.* to '*username*'@'*maxscalehost*';

**Query OK, 0 rows affected (0.00 sec)**
```

If you wish to use two different usernames for the two different roles of monitoring
and collecting user information then create a different username using the first
two steps from above.

## Creating additional grants for users

**Note:** The client host and MaxScale host must have the same username and
  password for both client and MaxScale hosts.

Because MariaDB MaxScale sits between the clients and the backend databases, the
backend databases will see all clients as if they were connecting from MariaDB
MaxScale's address. This usually requires users to create additional grants for
MariaDB MaxScale's hostname. The best way to describe this process is with an
example.

User `'jdoe'@'192.168.0.200` has the following grant on the cluster:
`GRANT SELECT, INSERT, UPDATE, DELETE ON *.* TO 'jdoe'@'192.168.0.200'`.
When the user connects directly to the server it will see it as
`'jdoe'@'192.168.0.200` connecting to the server and it will match
the grant for `'jdoe'@'192.168.0.200`.

If MariaDB MaxScale is at the address `192.168.0.101` and the user `jdoe`
connects to this MariaDB MaxScale, the backend server will see the connection as
`'jdoe'@'192.168.0.101'`. Since the backend server has no grants for
`'jdoe'@'192.168.0.101'`, the connection from MariaDB MaxScale to the server
will be refused.

We can fix this by either creating a matching grant for user `jdoe` from
the MariaDB MaxScale address or by using a wildcard to cover both addresses.

The quickest way to do this is by doing a SHOW GRANTS query:
```
MariaDB [(none)]> SHOW GRANTS FOR 'jdoe'@'192.168.0.200';
+-----------------------------------------------------------------------+
| Grants for jdoe@192.168.0.200                                         |
+-----------------------------------------------------------------------+
| GRANT SELECT, INSERT, UPDATE, DELETE ON *.* TO 'jdoe'@'192.168.0.200' |
+-----------------------------------------------------------------------+
1 row in set (0.01 sec)
```
Then creating the user `'jdoe'@'192.168.0.101'` and giving it the same grants:
```
MariaDB [(none)]> CREATE USER 'jdoe'@'192.168.0.101' IDENTIFIED BY 'secret_password';
Query OK, 0 rows affected (0.00 sec)

MariaDB [(none)]> GRANT SELECT, INSERT, UPDATE, DELETE ON *.* TO 'jdoe'@'192.168.0.101';
Query OK, 0 rows affected (0.00 sec)
```

The other option is to use a wildcard grant like the following:

```
GRANT SELECT, INSERT, UPDATE, DELETE ON *.* TO 'jdoe'@'%' IDENTIFIED BY 'secret_password'
```

This is more convenient but less secure than having specific grants for both the
client's address and MariaDB MaxScale's address as it allows access from all
hosts.

## Creating the configuration file

The configuration file creation is covered in different tutorials.

### Master-Slave cluster

* [MariaDB Replication Connection Routing Tutorial](MySQL-Replication-Connection-Routing-Tutorial.md)
* [MariaDB Replication Read-Write Splitting Tutorial](MySQL-Replication-Read-Write-Splitting-Tutorial.md)

### Galera cluster

* [Galera Cluster Connection Routing Tutorial](Galera-Cluster-Connection-Routing-Tutorial.md)
* [Galera Cluster Read Write Splitting Tutorial](Galera-Cluster-Read-Write-Splitting-Tutorial.md)
