MySQL InnoDB Cluster – Real-World Cluster Tutorial for OEL, Fedora, RHEL and CentOS

In this tutorial, we are going to guide you through the process of preparing and configuring RPM based distributions, such as OEL, Fedora or CentOS, for InnoDB cluster usage. We will address the steps from the initial configurations, to the cluster creation, and finally the MySQL Router configuration to map the data traffic.

A real world setup

In a real world setup, one would use real instances. However for explanatory purposes we will use Virtual machines to simulate a realistic setup as described in the previous tutorial.

Prerequisites

Python

Python is required to use MySQL Shell, please open a terminal and install it.

Fedora 25

CentOS 7 / Oracle Linux 7

Hostname mapping

Important: For this tutorial, we assume that the hostname mapping is already done. That is, the name of each host should be resolvable from the other hosts in the cluster.  If not, then please consider configuring the /etc/hosts file before continuing. Hostname mapping is required in order to map a valid hostname to an IP.

CentOS default hostname looks like the following:

To configure the host mapping open the hosts file:

Add the IP(s) of your host(s) and the name(s). Press ctrl+o and then enter to save the file. Press ctrl+x to close the file.

The file should have (something like) the following entries:

Install the MySQL YUM repository

Open a terminal and use wget to download the official APT repository and then install the package:

Fedora 25

CentOS 7 / Oracle Linux 7

Update the repositories once the installation of the APT repository is complete:

Fedora 25

CentOS 7 / Oracle Linux 7

Install MySQL Server and MySQL Shell

Type the following command in the terminal to install MySQL Server and MySQL Shell:

Fedora 25

CentOS 7 / Oracle Linux 7

After the installation of MySQL Server and MySQL Shell finish, start the MySQL service and enable it to start on the startup:

The remaining instructions are common for Fedora 25, CentOS 7 and Oracle Linux 7:

To enable remote connections, add a rule to the firewall and restart the firewall service:

To log in to MySQL Server, extract the temporary password that was set to root during the installation:

Since the temporary password has expired, the first thing to do is to set a new one for root. When the installation finish start MySQL using root user to update the password:

Exit MySQL and the start MySQL Shell using root user, type the password for root when asked for it:

Configure the local instance calling the following function. Type the password for the user when prompted:

MySQL Shell will find the default configuration file and ask you if it is ok to modify it, type “Y”. Since root cannot do remote logins, you have three options to continue with the configuration: enable the remote connections for root, create a new user or not enable remote connections for root neither create a new user.

Fedora screenshot

In this blog post, we choose to create a new user.

You will see a report with the changes made by MySQL Shell and a message saying that you need to restart the MySQL service to apply them.

Fedora screenshot

Quit MySQL Shell:

Restart the MySQL Service:

Once the restart of MySQL service is complete, start MySQL Shell and execute the following command:

If the instance configuration was successful, you shall receive a message saying that the instance is valid for cluster usage.

Fedora screenshot

The host is ready to be part of an InnoDB cluster.

Install MySQL Router

The next step is to install MySQL Router, which provides you the ability to hide your network configuration behind a proxy and map the data requests to the cluster.

In a terminal run the following command:

Fedora

CentOS / Oracle Linux 7

Once the installation of MySQL Router finish, it’s time to create a cluster.

Create an InnoDB cluster

Open a terminal and start MySQL Shell:

Then create a classic session to the host using the user created in the configuration step and the hostname of the host:

 

Fedora screenshot

Now create a cluster assigning the return value to a variable for later usage:

You will see a couple of messages with information about the cluster creation and the function required to add instances to it:


Fedora screenshot

If you have SELinux enabled this step may fail, because you may need to run additional commands to add a policy and enabled nis.

Once the cluster creation is complete, you can see the status of the cluster calling the following function:


Fedora screenshot

To add new instances use the following command, be sure to use a valid user and IP of an already configured host:

Type the password for the user when prompted. Add as many hosts as you want in your cluster, and take in mind that at least three are required to have tolerance to one failure.

Persist cluster configuration

In order to persist the cluster configuration of each instance, so if a restart happens the instances automatically rejoin the cluster, we must use the dba.configureLocalInstance() again on each instance. The command will update the my.cnf files with the parameters necessary for the automatic rejoin on the cluster on startup.

Run the following commands, locally on each instance:

Use MySQL Router

Now, it’s time to bootstrap our cluster. Open a new terminal and type the following command, and type the password for the user when requested:


Fedora screenshot

With the previous command the following it’s done:

  • A specific configuration for the cluster “myCluster” it’s created, MySQL Router got connected to the cluster and extracted the metadata to run by itself
  • A directory named “myrouter” is created in “home” and it contains the configuration required by MySQL Router to run
  • Four  TCP ports are generated to get connected to the cluster: rean only and read-write for classic protocol and X ptrotocol.

To start MySQL Router run the following command:


Fedora screenshot

To stop MySQL Router, in a terminal run the stop script generated:

 Remote Connection

Now we can get connected to the cluster using the IP generated by MySQL Router. The following screenshot is from a Windows host that is connected to the cluster using the read/write port:


Windows screenshot

And the following screenshot is from a windows host that it’s connected to the cluster using the read-only port:

Remember that to be able to connect to a remote host using its name, you should configure the host mapping in Windows as well. The file to edit it’s in the directory “C:\Windows\System32\drivers\etc\hosts”, once you configure the host mapping the file should looks like:

Conclusion

You’ve acquired the knowledge to configure hosts for cluster usage, as well as create cluster and add instances to it. Also, you have learned the basics to bootstrap a cluster and to create a proxy for remote connections to map the data traffic using MySQL Router. The environment can be tested as described in a previous tutorial.

You’ve certainly realized how simple and easy to use is the collection of products provided by MySQL to create a high availability environment.

See you in the next blog post!

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