How to Deploy PostgreSQL on Kubernetes?

Introduction

PostgreSQL is an open-source relational database management system (RDBMS) known for its robustness, stability, and ability to handle complex and large data sets. On the other hand, Kubernetes is an open-source container orchestration system that automates the deployment, scaling, and management of containerized applications.

Combining these two powerful technologies provides a highly scalable and reliable environment for hosting your PostgreSQL database. In this article, we will explore how to deploy PostgreSQL on Kubernetes.

We will start by explaining what PostgreSQL and Kubernetes are and the benefits of deploying PostgreSQL on Kubernetes. Then we will go through an overview of the deployment process before diving deep into each step.

Overview of the deployment process

The deployment process of PostgreSQL on Kubernetes involves several steps. We will go through each step in detail in the following sections. The overview of the deployment process includes −

• Setting up a Kubernetes Cluster − You can choose to use a cloud provider or set up a local cluster for development purposes.

• Preparing the PostgreSQL Image − Choose a base image for PostgreSQL deployment and configure it for use with Kubernetes.

• Creating a Deployment Manifest − Define the deployment specifications in YAML format and configure environment variables, volumes, and ports.

• Deploying PostgreSQL on Kubernetes − Use kubectl to deploy the manifest file and monitor the deployment status using kubectl commands.

• Scaling and Updating PostgreSQL − Scale up or down based on demand and update configurations or versions.

• Backing Up Data in PostgreSQL − Set up backups using pg_dump or pgBackrest and store backups in cloud storage.

Setting up a Kubernetes Cluster

Deploying PostgreSQL on Kubernetes requires a functioning Kubernetes cluster, which is a collection of nodes that work together to manage containerized applications. You can either create a cluster on your own machines or use cloud providers like Amazon Web Services (AWS), Google Cloud Platform (GCP), or Microsoft Azure. Cloud provider options vary in terms of pricing, features, and supported versions of Kubernetes.

Choosing a cloud provider or setting up a local cluster

Before choosing between cloud providers or setting up a local cluster, consider factors such as cost-effectiveness, infrastructure management skills and team size, compliance requirements and application needs. Cloud providers offer managed services that handle the underlying infrastructure management while providing easy-to-use interfaces to spin up clusters with minimal setup required. The downside is the potential cost over time when compared to maintaining an in-house solution.

Installing and configuring kubectl and Helm

Once you have set up your Kubernetes Cluster it is time to install kubectl which is an essential tool used to interact with the Kubernetes API server. Kubectl allows developers to deploy applications onto their newly created clusters by providing access to pods/services/replication controllers/configMaps/secrets etc.

Helm can be installed using package managers available on most operating systems, like apt or brew for macOS and Linux. Once installed, you can use the helm command to interact with charts.

Preparing the PostgreSQL Image

Before deploying PostgreSQL on Kubernetes, you need to prepare a Docker image that includes the necessary software and configuration. You can start with a base image of PostgreSQL from Docker Hub, or you can build your own custom image with additional components.

Choosing a base image for PostgreSQL deployment The base image of PostgreSQL includes the operating system, Postgres binaries, and some basic configuration.

Configuring the Image for use with Kubernetes

Once you have chosen a base image for your deployment of Postgres on Kubernetes, it is time to configure it for use within Kubernetes. To make your containerized Postgres instance work within Kubernetes in an optimal way requires setting some environment variables in its container specification. For instance −

• POSTGRES_USER − sets up an initial user account. - POSTGRES_PASSWORD: sets up an initial password.

• POSTGRES_DB − specifies which database to connect to by default. The kubectl create command line utility allows us to create or modify these environment variables using YAML files.

Creating a Deployment Manifest

Once you have set up your Kubernetes cluster and prepared the PostgreSQL image, the next step is to create a deployment manifest. A deployment manifest is a YAML file that defines the specifications for the deployment of PostgreSQL on Kubernetes. In this file, you can specify various parameters such as the number of replicas, pod labels, container images, and more.

Defining Deployment Specifications in YAML Format

A deployment manifest is typically written in YAML format and consists of several sections that define the various components of your PostgreSQL deployment. At the top level, you need to specify metadata such as name and labels for your deployment. You also need to define the desired number of replicas that should be deployed.

Inside each replica specification, you need to specify which container image should be used to run PostgreSQL and other details such as resource limits and requests.

Configuring Environment Variables, Volumes and Ports

The environment variables section allows you to set values for all sorts of different configuration options within PostgresSQL like database name or password or server port which are defined inside postgresql.conf file etc.. This makes it easy to manage configuration across multiple deployments or environments.

Volumes are used to store data persistently across restarts or upgrades of applications running within containers. In order for a volume to work with a container running PostgreSQL on Kubernetes, it must be mounted at a specific location inside the container's filesystem.

Deploying PostgreSQL on Kubernetes

Once the manifest file is created, deploying PostgreSQL on Kubernetes is a straightforward process using kubectl. Before deploying, ensure that the Kubernetes context is set to the correct cluster, and that kubectl has access to it. To deploy, simply run the following command in the directory containing the manifest file −

kubectl apply -f postgres-manifest.yaml     

Kubernetes will begin creating pods based on the specifications defined in the manifest file.

Once all pods are running and ready, PostgreSQL will be accessible through a service object, which can be accessed using its ClusterIP or NodePort. The service object abstracts away any changes to pod IP addresses or node ports.

Using kubectl to deploy the manifest file

The `kubectl apply` command allows you to create or update resources from a YAML or JSON file without having to manually define each resource separately with `kubectl create`. If you make changes to your deployment specifications in your manifest file, you can use `kubectl apply` again to update your deployment. You can also use `kubectl get` commands to view information about your deployment status.

Monitoring the deployment status using kubectl commands

Monitoring is an important aspect of any production system. In Kubernetes, there are several ways to monitor a deployed application's status using kubectl commands.

You can check pod statuses with `kubectl get pods`, which shows if each pod is running or not. If a pod has restarted recently due to an error or crash loopback off error (liveness probe failed), it may be helpful to see its logs with −

kubectl logs       

If you want to see metrics on resource usage, you can use `kubectl top`.

Conclusion

Deploying PostgreSQL on Kubernetes provides many benefits that make it a compelling option for organizations that use PostgreSQL. Firstly, it makes scaling and updating of your database much easier as Kubernetes provides automated scaling and rolling updates.

Secondly, the use of containerization allows for better resource utilization, making it possible to run multiple database instances on a single machine. Additionally, deploying PostgreSQL on Kubernetes provides improved reliability through the use of replicas and automatic failover mechanisms.