Setting up MySQL Replication Cluster in Kubernetes

Setting up MySQL Replication
Clusters in KUBERNETES

How to Setup your MySQL Replication Cluster
We will use a traditional slave/master set up with asynchronous replication,
configurable replication, depending on user configuration, and no
requirement for a constant connection. For the official line on MySQL and
more information plus technical details around replication, check out
the MySQL documentation.
You can find this and more K8S tutorials with copy
& paste-friendly code and links at blog.kublr.com

Install Vagrant on your Host Machine
In this example, we are using Vagrant as a configuration manager on Mac
OS X to create the Kubernetes environment. To follow this guide, please
install Vagrant on your host machine. You will also need a virtualization tool,
for example Oracle’s Virtual Box or VMware Fusion.

Setting up the K8S Environment
With a variety of ways to configure and setup your Kubernetes cluster, your
existing system may vary. In this instance, we are using Vagrant
(the Vagrantfile is provided by the CoreOS setup guide), to set up the
environment, making use of a single controller node and a set of three
worker (slave) nodes.

After setting up Vagrant, check the state of the environment by running
these commands…

This environment represents multiple VMs. The VMs are all listed
above with their current state. For more information about a specific
VM, run`vagrant status NAME'.
e1 is etcd node, c1 is controller node, and w1, w2, w3 are worker nodes.

Prepare Your MySQL Docker Image
Build the Docker Image
Having setup the replication cluster, we’ll modify the Docker file and build a
Docker image with MySQL. Again, we follow the official guidance based on
the MySQL Docker image.
For the master:
Edit the Dockerfile, and add the following lines:

Edit docker-entrypoint.sh file to create a user and password for replication:
We use environment
variables MYSQL_REPLICATION_USER and MYSQL_REPLICATION_PASSWORD for user and
password configuration. These environment variables will be set while the pod is created in
Kubernetes.
Click the link to view the dockerfile and docker-entrypoint.sh for building the master.

For the slave:
Edit the Dockerfile, and add the following lines:
The server-id use random number.
Edit docker-entrypoint.sh to add the master.

The master host is MYSQL_MASTER_SERVICE_HOST which will be the
service name of the master pod in Kubernetes. For more information
visit Kubernetes’ container lifecycle hooks guide.
Click the link to view the docker-entrypoint.sh for building the slave.
Finally, we can build the MySQL Master image and the MySQL Slave images,
based on their Dockerfile.

Deploy to Kubernetes
We now deploy the MySQL replication cluster to kubernetes using
the kubectl command.

Deploy MySQL Master
Create a replication controller and service for
the MySQL Master node. The yaml file we
use to create replication controller and
service are:

Deploy MySQL Master
Now, we will use kubectl to ar the controller and service:
It will take some time to create the pod because it needs to download the
docker image.

Deploy MySQL Slave
As with the master node, we will
use two yaml files to create the
replication controller and service
for the MySQL slave.

Deploy MySQL Slave
Now, we will use kubectl to add the
controller and service:
After these tasks have been
performed, we should check the
status through kubectl.

Create Your Database on Master
First, we will check the MySQL
status both on master and slave. Go
to the master pod and execute the
following commands to check the
MySQL status (follow the same
steps for the slave node). =>
Note
mysql-master-95j7d is the name of
master pod and the root password of
MySQL is test.

Create Your Database on Master
Then, create a database and add
one table with a several rows.
On the master node, we do:

Check Synchronization on Slave
Go to the slave node kubectl
exec -it mysql-slave-gr41w
/bin/bash and ensure the table
has been replicated =>
All data should now be
synchronized.

Replication Controller Scaling
Now that we have one MySQL master pod and one MySQL slave pod, we
can do some scaling. For example, set MySQL slave node to three.
You can see it’s creating now, after few time, the nodes will be ready and
we can enter one of them to check the MySQL data synchronization.

Making MySQL Data Persistent
In your production environment,
configure the volume mount for
MySQL data persistent, the yaml
file for creating replication
controller is as below =>
The Mount
path /var/lib/mysql is just the
same as defined in Dockerfile.

THANK YOU!
Kublr (kublr.com) is a production-ready cluster and application platform
that speeds and simplifies the set up and management of Kubernetes for
your applications.
For more Kubernetest tutorials, visit our blog at blog.kublr.com.
Want to learn more about Kublr? Contact us at contact@kublr.com

Setting up MySQL Replication Cluster in Kubernetes

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