Before You Start v1.2.0

Before you get started, it's essential that you become familiar with some terminology that's specific to Kubernetes and PGD.

Kubernetes terminology

Node : A node is a worker machine in Kubernetes, either virtual or physical, where all services necessary to run pods are managed by the control plane nodes.

Pod : A pod is the smallest computing unit that can be deployed in a Kubernetes cluster and is composed of one or more containers that share network and storage.

Service : A service is an abstraction that exposes as a network service an application that runs on a group of pods and standardizes important features, such as service discovery across applications, load balancing, and failover.

Secret : A secret is an object that's designed to store small amounts of sensitive data, such as passwords, access keys, or tokens, for use within pods.

Storage class : A storage class allows an administrator to define the classes of storage in a cluster, including provisioner (such as AWS EBS), reclaim policies, mount options, volume expansion, and so on.

Persistent volume : A persistent volume (PV) is a resource in a Kubernetes cluster that represents storage that was either manually provisioned by an administrator or dynamically provisioned by a storage class controller. A PV is associated with a pod using a persistent volume claim, and its lifecycle is independent of any pod that uses it. Normally, a PV is a network volume, especially in the public cloud. A local persistent volume (LPV) is a persistent volume that exists only on the particular node where the pod that uses it is running.

Persistent volume claim : A persistent volume claim (PVC) represents a request for storage, which might include size, access mode, or a particular storage class. Similar to how a pod consumes node resources, a PVC consumes the resources of a PV.

Namespace : A namespace is a logical and isolated subset of a Kubernetes cluster and can be seen as a virtual cluster within the wider physical cluster. Namespaces allow administrators to create separated environments based on projects, departments, teams, and so on.

RBAC : Role-based access control (RBAC), also known as role-based security, is a method used in computer systems security to restrict access to the network and resources of a system to authorized users only. Kubernetes has a native API to control roles at the namespace and cluster level and associate them with specific resources and individuals.

CRD : A custom resource definition (CRD) is an extension of the Kubernetes API and allows developers to create new data types and objects, called custom resources.

Operator : An operator is a Kubernetes software extension that automates those steps that are normally performed by a human operator when managing one or more applications or given services. An operator assists Kubernetes in making sure that the resource's defined state always matches the observed one.

kubectl : kubectl is the command-line tool used to manage a Kubernetes cluster.

EDB Postgres® AI for CloudNativePG™ Global Cluster (CNPG-GC) requires a Kubernetes version supported by the community. See Supported releases for details.

PGD terminology

For more information, see Terminology in the PGD documentation.

Data node : A PGD database instance.

Failover : The automated process that recognizes a failure in a highly available database cluster and takes action to connect the application to another active database.

Switchover : A planned change in connection between the application and the active database node in a cluster, typically done for maintenance.

Write leader : In always-on architectures, a node is selected as the correct connection endpoint for applications. This node is called the write leader. The write leader is selected by consensus of a quorum of data nodes.

Cloud terminology

Region : A region in the cloud is an isolated and independent geographic area organized in availability zones. Zones within a region have very little round-trip network latency.

Zone : An availability zone in the cloud (also known as a zone) is an area in a region where resources can be deployed. Usually, an availability zone corresponds to a data center or an isolated building of the same data center.

What to do next

Now that you are familiar with the terminology, you can test CNPG-GC on your laptop using a local cluster before deploying the operator in your selected cloud environment.