Part 12 – Kubernetes Interview Questions & Answers (Q.56 to Q.60)

Q.56 Describe the process of setting up a Kubernetes federation for global deployments.

Host Cluster Installation: Set up a dedicated Kubernetes cluster to act as the federation “host” where control plane components will reside.
Member Cluster Preparation: Ensure you have multiple Kubernetes clusters running geographically or topologically distinct (different cloud providers, etc.) These will join the federation.
Deploy Federation Control Plane: Install the required control plane components in the host cluster (API server, controller-manager).
Join Member Clusters: Install federation agents on each member cluster that you want to federate.
Create Federated Resources: Choose which existing Kubernetes object kinds (Deployments, Services, etc.) you want to be federated using CRDs.
Configuration and Policies: Use tools like kubefedctl to manage cross-cluster replication, placement across zones, and overall federation rules.

Use Cases:

Geographically distributed workloads: Manage applications close to users across zones for low latency, or disaster recovery with failover to alternate regions.
Multi-cloud or hybrid-cloud scenarios: Span Kubernetes clusters across different cloud providers or on-premises deployments.

Strong Authentication: Enforce robust authentication for access (avoid basic auth). Consider TLS client certificates or integrating with an external identity provider.
Fine-grained Authorization: Utilize Kubernetes Role-Based Access Control (RBAC) to implement the principle of least privilege.
TLS Encryption: Always use TLS to encrypt communication to the API server. Protect both internal and external traffic.
Limit Network Access: Restrict access using firewalls or Network Policies – allow only necessary sources to reach the API server.
Audit Logging: Enable audit logging to track all API server requests for security analysis and incident response.
Regular Updates: Patch your Kubernetes components to promptly address known vulnerabilities.

Use Cases:

Prevent unauthorized access: Keep sensitive cluster data and configuration safe from intruders.
Compliance: Meet strict security standards required in regulated industries.

Example:

Integrate the API server with an SSO provider for authentication, and use RBAC to control access to different areas of the cluster.

StatefulSets: StatefulSets provide pod identity and manage ordered, graceful updates and rollbacks of stateful applications.
Update Strategies: StatefulSets offer two main update strategies:
- RollingUpdate: Gradual pod replacement, important for maintaining availability.
- OnDelete: Updates pods manually for fine-grained control, often requiring downtime.
Persistent Storage: Use Persistent Volumes and Persistent Volume Claims to ensure each new pod can attach to its designated data.
Application Awareness: Ensure your application itself handles data synchronization or replication on pod replacement or failover.

Use Cases

Example:

StatefulSet for MongoDB with a RollingUpdate strategy allowing one replica to be updated at a time.

Handling Complexity: Operators address managing applications as complex as databases, message queues, or even other Kubernetes clusters. They automate complex administrative tasks.
Operational Knowledge as Code: Operators codify deployment, upgrades, reconfiguration, backup/restore, and failure recovery workflows as software logic.
Extending Kubernetes: Operators add application-specific intelligence and control loops into Kubernetes through CRDs and controllers.

Use Cases:

Stateful Sets: Operators simplify the lifecycle management of stateful applications that otherwise require manual intervention.
External dependencies: Manage interaction with cloud services, databases not in Kubernetes, or custom infrastructure.
Day 2 Operations: Automaticity and codified knowledge lead to self-managing applications beyond initial deployment.

Example:

A Prometheus Operator installs Prometheus server, sets up configurations, manages alert rules, and scales as monitoring needs change.

Redundant Clusters: Distribute workloads across multiple clusters in different geographic regions or failure domains.
HA Architecture: Design applications and clusters with high availability within each cluster as well (see earlier questions on HA).
Regular Backups: Back up the state of etcd and application data, and store these backups off-cluster in a safe location.
Recovery Procedures: Have well-defined and tested recovery plans to minimize downtime during failures. Automation plays a key role.
DR Testing: Regularly simulate failures and test the entire disaster recovery process to ensure it works in practice.

Use Cases:

Example:

Two regional Kubernetes clusters.
Backups of both etcd and stateful application data to cloud object storage.
A documented plan for failing over to the recovery cluster, potentially using automation tools to speed the process.

Hope you find this post helpful.