Demystifying Kubernetes in 5 Minutes

Kubernetes is not new and has been a de-facto standard of deployments and CI/CD at most companies for a while. The goal of this article is to make you familiar with all the terms and jargon that Kubernetes experts use, in approximately 5 minutes!

Introduction to Kubernetes

Kubernetes provides a scalable framework to manage containers, offering features that span basic cluster architecture to advanced workload orchestration. This piece goes over both the basic and advanced features of Kubernetes. It talks about architecture, resource management, layered security, and networking solutions. It ends with looking at service meshes and persistent storage.

Building Blocks

Kubernetes operates on a cluster architecture comprising control plane nodes and worker nodes. I sometimes like to refer to "worker nodes" as data planes.

• The control plane coordinates the cluster, with core components such as:
  • API Server: Manages all cluster operations via RESTful APIs
  • Scheduler: Assigns pods to nodes based on resource availability and policies
  • Controllers: Align cluster state with desired configurations (e.g., ReplicaSets, Deployments)
  • etcd: Provides a robust key-value store for all cluster data
• The Data Plane hosts application workloads and includes:
  • Kubelet: Manages pod execution and node operations
  • Kube-proxy: Configures networking rules to connect pods
  • Container Runtime: Runs containers using tools like containerd, which is open source

Refer to the Kubernetes API reference guide for detailed component insights.

Resource Management

Kubernetes organizes workloads into logical resources such as:

• Pods: The smallest deployable unit, often hosting one or more containers
• Deployments: Manage stateless workloads with rolling updates and scaling
• StatefulSets: Provide persistent storage and ordered scheduling for stateful applications
• DaemonSets: Ensures that system-level pods are set up on all nodes

Security Measures

Security is a top priority in cloud-native environments, and Kubernetes provides a comprehensive suite of features to address this need. Kubernetes offers several security features, including:

• RBAC: Role-Based Access Control (RBAC) lets you be very specific about who in the cluster can see what; it is often also referred to as ACLs (Access Control Lists).
• Network Policies: Network Policies enable you to regulate communication between Pods, adding an extra layer of protection by isolating sensitive workloads.
• Secrets: Secrets are a safe way to store sensitive credentials, keeping important information private and avoiding accidental exposure.

Networking

Kubernetes adopts a flat networking model where all pods communicate seamlessly across nodes. Key networking features include:

• Services: Expose pods to network traffic, enabling internal and external access.
• Ingress: Manages external HTTP traffic with routing rules.
• Network Policies: Control ingress and egress traffic for pods, enhancing security.

Service Mesh for Microservices

Complex microservices often require advanced communication capabilities beyond Kubernetes services. Service meshes like Istio, Linkerd, and Consul provide:

• Automated mTLS encryption for secure service-to-service comms
• Traffic routing, observability, and even load balancing
• Support for A/B testing, circuit breaking, and traffic splitting

These tools eliminate the need for custom-coded communication logic, streamlining development.

Persistent Storage for Stateful Workloads

Kubernetes supports persistent storage via the Container Storage Interface (CSI), enabling integration with diverse storage backends. This only makes sense though if your application is stateful (or, using StatefulSets). 

Key resources include:

• PersistentVolumes (PV): Represent physical or cloud-based storage
• PersistentVolumeClaims (PVC): Allow workloads to request storage dynamically
• StorageClasses: Simplify storage configuration for diverse workload needs

StatefulSets combined with PVCs ensure data durability even during pod rescheduling.

Performance: Azure Kubernetes Service As Example

Performance really depends on how large the container image that you are running is.

Managed solutions like Azure Kubernetes Service provide all of these mentioned above, plus, offer the reliability of Azure behind it. Azure enhanced its infrastructure to reduce the container startup time by pre-caching common base images, so customers can see 15-20x performance gain on cold container startups [1].

Conclusion

As I said earlier, unless you are living under a rock, Kubernetes has become an essential tool for organizations embracing cloud-native practices. Its robust, decoupled architecture, combined with strong security features, allows for the efficient deployment and management of containerized applications. For further learning, consult the official Kubernetes documentation.

References

1. US11966769B2 - Container instantiation with union file system layer mounts- Google Patents. Hotinger, E. R., Du, B., Antony, S., Lasker, S. M., Garudayagari, S., You, D., Wang, Y., Shah, S., Goff, B. T., Zhang, S., & Llc, M. T. L. (2019, May 23).