Kubernetes (also known as K8s) is an open-source container orchestration platform that automates the deployment, scaling, and management of containerized applications. It assists with container orchestration by providing the following functionalities:
1. **Container deployment**: Kubernetes allows you to define your application deployment using declarative configuration files (typically in YAML format). You can specify the desired number of replicas for each container, networking, storage, and other configurations.
2. **Scaling**: Kubernetes can be configured to automatically scale the number of replicas for a container, based on CPU utilization or custom metrics. The Kubernetes Horizontal Pod Autoscaler (HPA) takes care of scaling your application up or down in response to demand. The formula used for scaling is:
desiredReplicas = ceil[currentReplicas * (currentMetricValue/desiredMetricValue)]
3. **Load balancing**: Kubernetes comes with built-in load balancing capabilities via services and ingress controllers. This allows the platform to distribute traffic among multiple replicas of an application, ensuring that no single instance becomes a bottleneck.
4. **Rolling updates and rollback**: Kubernetes allows you to perform updates to your containerized applications with minimal downtime by using a strategy called rolling updates. This process involves gradually replacing old replicas with new ones while maintaining availability. If something goes wrong, you can easily roll back the update.
5. **Self-healing**: Kubernetes automatically monitors the health of your containers, and if a container fails a health check or stops responding, Kubernetes will restart the container or replace it with a new replica.
6. **Storage management**: Kubernetes provides a storage management system called Persistent Volumes (PV) and Persistent Volume Claims (PVC). PVs represent physical storage resources in a cluster, while PVCs are used by applications to request a specific amount of storage. This abstracts the underlying details about storage provision from developers, making it easier for them to create applications that require storage.
7. **Secrets management**: Kubernetes has built-in support for managing sensitive information like passwords, tokens, and API keys using secrets. Applications can easily consume these secrets without exposing them in configuration files or container images.
In summary, Kubernetes greatly eases the process of managing containerized applications by providing a comprehensive set of features that handle deployment, scaling, load balancing, rolling updates, self-healing, storage, and secrets management. This allows developers and operators to focus on application development and delivering new features rather than the nitty-gritty details of infrastructure management.