Architecture and Orchestration of Scaleway Managed Kubernetes: Kapsule and Kosmos Ecosystems

The modern landscape of containerized application deployment necessitates a robust, scalable, and highly available orchestration layer. Scaleway addresses these requirements through its specialized managed Kubernetes offerings, specifically designed to abstract the heavy lifting of infrastructure management. By leveraging managed services, organizations can bypass the grueling operational overhead typically associated with maintaining a Kubernetes control plane, shifting their engineering focus from cluster maintenance to application logic and service delivery. This architecture is realized through two primary products: Kubernetes Kapsule and Kubernetes Kosmos. While both products aim to simplify the lifecycle of containerized workloads, they serve distinct operational philosophies regarding infrastructure locality and cloud-native flexibility.

The Managed Kubernetes Paradigm: Kapsule vs. Kosmos

In the context of Scaleway's ecosystem, the term "managed Kubernetes" refers to a division of labor between the cloud provider and the end-user. Scaleway assumes responsibility for the foundational, high-availability components required to keep a cluster operational, while the user retains control over the applications, configurations, and specific resource deployments.

The distinction between Kapsule and Kosmos is fundamental to how a cluster interacts with underlying hardware. Kubernetes Kapsule is the classic, integrated managed Kubernetes offering where all nodes and their associated Pods are hosted directly on Scaleway Instances. This provides a unified, high-performance environment where the network and compute are tightly integrated within the Scaleway infrastructure.

In contrast, Kubernetes Kosmos provides a multi-cloud orchestration capability. Kosmos is designed for environments where Pods may be hosted on nodes residing in different cloud providers, offering a level of flexibility for organizations requiring multi-cloud strategies or specific hybrid-cloud architectures. By choosing Kapsule, a developer chooses a streamlined, single-provider experience; by choosing Kosmos, they choose an expansive, multi-cloud orchestration model.

Core Component Management and Control Plane Abstraction

The most significant advantage of utilizing Scaleway's managed services is the abstraction of the Kubernetes control plane. The control plane serves as the brain of the cluster, making decisions about scheduling, responding to cluster events, and managing the state of the system. In a manual setup, the failure of a single control plane component can lead to total cluster instability. Scaleway mitigates this risk by handling the management and maintenance of all crucial core components.

The managed control plane includes several critical Kubernetes components that Scaleway manages to ensure the cluster's operational integrity:

• etcd: The distributed key-value store that serves as the cluster's primary database, maintaining the state of every object within the system.
• API server: The central communication hub that exposes the Kubernetes API, allowing users and internal components to interact with the cluster.
• Scheduler: The component responsible for assigning Pods to specific nodes based on resource requirements, hardware constraints, and policy.
• Cloud controller: A specialized controller that allows Kubernetes to interact with the Scaleway cloud infrastructure (see the Scaleway Cloud Controller Manager section for details).
• Controller manager: The component that runs various control loops to regulate the state of the cluster, such as node controllers and replication controllers.

Beyond these core brain components, Scaleway manages the essential system applications required for the optimal functioning of the cluster. These "system-level" services are vital for networking, storage, and service discovery. These include:

• CoreDNS: The internal service discovery mechanism that allows Pods to find each other via DNS names.
• Kubeproxy: The component that maintains network rules on nodes, allowing for effective communication between Pods and services.
• Container Networking Interface (CNI): The standard that facilitates the configuration of network interfaces in Pods.
• Container Storage Interface (CSI): The standard that allows for the attachment and detachment of storage volumes to the containers.

The impact of this managed approach is a significant reduction in "undifferentiated heavy lifting." Because Scaleway manages node provisioning and provides updated operating system node images, administrators do not need to manually patch the underlying OS or worry about the lifecycle of the node's base image.

Scaleway Cloud Controller Manager (SCCM) Implementation

To bridge the gap between the Kubernetes API and Scaleway's specific hardware and networking APIs, Scaleway utilizes a custom implementation of the Kubernetes cloud-provider interface. This is achieved through the scaleway-cloud-controller-manager.

The Kubernetes architecture allows for "out-of-tree" cloud providers, which are controllers that implement provider-specific control loops. The Scaleway implementation is an active development project (currently in alpha) that performs several critical functions to ensure the cluster is "cloud-aware."

The SCCM implements several key interfaces:

• Instances interface: This logic ensures that Kubernetes nodes are correctly labeled and addressed with provider-specific metadata. Crucially, it also handles the cleanup process, deleting the Kubernetes node object when the corresponding instance is terminated in the Scaleway console.
• LoadBalancer interface: This is essential for external access. When a user creates a Kubernetes Service of type: LoadBalancer, the SCCM detects this request and automatically triggers the creation of a Scaleway Load Balancer to route external traffic to the cluster.
• Zone interface: This provides the scheduler with awareness of the geographical "failure domains" (Availability Zones) of each node, allowing for more resilient application deployment strategies.

Cluster Lifecycle and Configuration Workflows

Creating and managing a cluster within the Scaleway ecosystem follows a structured workflow, accessible via the Scaleway console, the CLI, or Infrastructure as Code (IaC) tools.

To initiate the deployment of a cluster, an administrator must possess the appropriate IAM permissions or Owner status within their Scaleway Organization. The process begins in the Kubernetes section of the Scaleway console.

The creation wizard requires several critical configuration parameters:

• Organization and Project: Defining the administrative boundary for the new cluster.
• Cluster Type: Selecting either Kapsule (using Scaleway Instances) or Kosmos.
• Geographical Region: Selecting a deployment location, such as Paris (France), Amsterdam (Netherlands), or Warsaw (Poland).
• Control Plane Offer: Choosing between a "Shared" control plane (cost-effective) or a "Dedicated" control plane (higher performance and isolation).
• Kubernetes Version: Specifying the version of the K8s engine.

Once a cluster is created, its lifecycle can be managed through various interfaces. Scaleway emphasizes flexibility by supporting:

• kubectl: The standard Kubernetes command-line tool for direct cluster interaction.
• Scaleway CLI and API: For programmatic management of cluster resources.
• Terraform/OpenTofu: For implementing Infrastructure as Code, allowing users to version-control their entire cluster architecture.
• Application Library: For one-click deployments of pre-configured container images.
• Helm Integration: Allowing users to deploy complex, multi-component applications via the Scaleway console with a few clicks.

Scaling, Resilience, and High Availability

Scalability is a core pillar of the Kapsule and Kosmos architectures. Scaleway allows for both horizontal and vertical scaling, enabling the cluster to adapt to fluctuating workloads.

Horizontal scaling is achieved through the use of "Node Pools." An administrator can add or remove entire pools of nodes to increase or decrease the total computational power available to the cluster. This ensures that as an application's demand grows, the underlying infrastructure can expand to meet that demand without manual reconfiguration of existing nodes.

Vertical scaling involves adjusting the resource limits and requests for individual Pods or the instance types within a pool.

To ensure high availability and "uninterrupted performance," Scaleway implements automated health checks and an "autoheal" mechanism. The system monitors the responsiveness of nodes continuously. If a node becomes unresponsive for a duration exceeding 15 minutes, Kapsule takes automated action to restart or replace the failing node. This automated remediation minimizes downtime and reduces the need for manual intervention during hardware or software failures.

Furthermore, all Kapsule clusters are provisioned with an attached Private Network by default. This ensures that all inter-node and inter-pod communication remains private and secure within the Scaleway network, isolating the cluster's internal traffic from the public internet.

Responsibility and Security Boundaries

A clear demarcation of responsibility exists between Scaleway and the user. Misunderstanding this boundary is a common source of downtime and security vulnerabilities in managed Kubernetes environments.

Scaleway's responsibilities include:
- Managing the control plane and its components.
- Node provisioning and OS image updates.
- Providing updates for Kubernetes minor releases and patches.
- Offering maintenance schedules for automatic patch application.
- Managing system-level components like Kubelet on the nodes (unless modified by the user).

The user's responsibilities include:
- Deploying and managing the application workloads.
- Managing the configuration of all resources deployed to the cluster.
- Applying security patches and updates to the applications and user-managed configurations.
- Maintaining security for any preinstalled components if the user chooses to modify them at the node or system level.

Failure to apply security updates at the application layer can compromise the cluster's overall security posture, even if the underlying infrastructure is perfectly maintained by Scaleway.

Technical Specification Summary

The following table summarizes the operational parameters and service features of the Scaleway Kubernetes ecosystem.

Detailed Analysis of Versioning and Lifecycle Management

Scaleway adopts a proactive approach to versioning, which is critical for maintaining a stable and secure production environment. Kubernetes releases are frequent, and staying current is necessary to leverage new features and security fixes.

Scaleway supports at least the latest version of the last three major Kubernetes releases. This provides a window of stability for users to test new versions before upgrading their production workloads. To facilitate this, Scaleway provides a maintenance scheduler. This tool automates the application of Kubernetes patch releases, ensuring that the control plane remains secure without requiring constant manual intervention from the user.

However, users must remain vigilant regarding the end-of-life (EOL) of older versions. Scaleway provides information and reminders when specific Kubernetes versions reach their end of support. This notification system is designed to allow administrators to plan their upgrade paths through their preferred deployment method—be it through the console, kubectl, or Terraform—to avoid running unsupported, potentially insecure software.

In conclusion, Scaleway's managed Kubernetes offerings provide a sophisticated, multi-tiered approach to container orchestration. By abstracting the complexities of the control plane and system-level networking, and by providing robust tools for scaling and automation, Scaleway enables a rapid transition from application development to large-scale production deployment. Whether through the integrated simplicity of Kapsule or the multi-cloud flexibility of Kosmos, the platform provides the necessary infrastructure to maintain high-performance, resilient, and secure containerized environments.

Sources

1. Scaleway Documentation: Managed Kubernetes Service Definition
2. Scaleway Documentation: Kubernetes Quickstart
3. Scaleway Product Page: Kubernetes Kapsule
4. GitHub: Scaleway Cloud Controller Manager
5. Scaleway Tutorial: Deploying Kapsule