Deployment is a resource object used to manage the deployment and scaling of applications. It provides declarative updates to applications, ensuring that a specified number of pod replicas are running at any given time. Deployments are essential for managing the lifecycle of applications in a Kubernetes cluster, enabling features such as rolling updates, rollback to previous versions, and scaling.
Key Features of Deployments:
Declarative Updates:
Deployments allow users to declare the desired state of their applications using YAML or JSON manifests.
Users specify the desired number of replicas, container images, resource requirements, and other configuration details.
Rolling Updates:
Deployments facilitate rolling updates by gradually updating pods to a new version while maintaining application availability.
During a rolling update, Deployments create new pods with the updated version and gradually replace the old pods, ensuring zero-downtime updates.
Rollback:
If issues arise during an update, Deployments support automatic or manual rollback to the previous stable version.
This feature provides a safety net for managing application updates and mitigating risks.
Scaling:
Deployments support horizontal scaling of applications by adjusting the number of replicas based on demand.
Scaling can be performed manually or automatically based on predefined metrics such as CPU utilization or custom metrics.
Self-Healing:
Deployments ensure application availability by automatically restarting failed pods and maintaining the desired number of replicas.
If a pod becomes unhealthy or unresponsive, the Deployment controller replaces it with a new pod.