Hybrid Multicloud Deployment of SLIM

[muscariello]

Proposal: Multi-Cluster Deployment of SLIM Nodes via Controller

This document proposes a hierarchical, GitOps-based architecture to deploy and manage SLIM nodes across multiple Kubernetes clusters—both in public and private clouds. By leveraging a multi-cluster management layer (e.g., Sveltos), we can treat SLIM as a cluster add-on and ensure consistent, scalable rollout.

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1. Architecture Overview

flowchart LR
  subgraph GitOps Pipeline
    Repo["Git Repository<br />(SLIM Manifests)"]
    Argo["Flux / ArgoCD"]
  end

  subgraph Multi-Cluster Management
    Sveltos["Sveltos Controller
 (GitOps + Policies)"]
    Cluster1[Kube Cluster A]
    Cluster2[Kube Cluster B]
    ClusterN[Kube Cluster N]
  end

  Repo --> Argo
  Argo --> Sveltos
  Sveltos --> Cluster1
  Sveltos --> Cluster2
  Sveltos --> ClusterN

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1. GitOps Pipeline: A central Git repository holds all SLIM deployment manifests, Helm charts, and custom resource definitions (CRDs).
2. Multi-Cluster Management: Sveltos watches both the Git repository and cluster inventory, reconciling clusters according to defined policies.
3. Cluster Add-on: SLIM components (controller, CRDs, RBAC) are installed as a managed add-on in each cluster.

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2. Deployment Workflow

1. Developer or Admin updates SLIM Helm chart or CR manifests in the Git repository (main branch).
2. Flux/ArgoCD syncs changes into the Sveltos management plane.
3. Sveltos applies/adds the SLIM add-on to each registered cluster, ensuring policy compliance and drift correction.

graph TD
  Git["Git Repo <br />(slim-manifests)"] -->|push| Argo["Flux / ArgoCD"]
  Argo -->|sync| Sveltos["Sveltos Management Plane"]
  Sveltos --> Cluster1["Cluster A Add-on: SLIM"]
  Sveltos --> Cluster2["Cluster B Add-on: SLIM"]
  Sveltos --> ClusterN["Cluster N Add-on: SLIM"]

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3. GitOps Best Practices

• Branch Strategy: Use feature branches for changes, pull requests for code review.
• Policy-as-Code: Define Sveltos policies (e.g., namespace whitelisting, image registry rules) alongside CRDs.
• Automated Testing: Integrate CI to validate Helm charts and CRDs before merging.

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4. Sveltos Hybrid Cloud Use Case

Sveltos supports hybrid/multi-cloud scenarios as described in the Hybrid Multicloud Use Case. Leveraging Sveltos:

• Cluster Registration: Enroll clusters via GitOps-managed cluster inventory.
• Policy Enforcement: Enforce security, network, and SLIM-specific policies across all clusters.
• Lifecycle Management: Automatically upgrade SLIM add-on when new versions are merged.

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5. Administrative Operations

• Cluster Onboarding: Admin creates a Cluster resource in the management Git repo; Sveltos enrolls the cluster.
• Scaling: Policies can define which clusters run which SLIM profiles (e.g., dev vs. prod).
• Monitoring & Alerts: Central control-plane collects metrics via Prometheus Adapter in each cluster.

sequenceDiagram
    participant Admin
    participant GitRepo
    participant Sveltos
    participant Cluster

    Admin->>GitRepo: Add Cluster resource
    GitRepo->>Sveltos: Sync changes
    Sveltos->>Cluster: Enroll & apply SLIM CRDs
    Cluster-->>Admin: Ready status

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6. Conclusion

This hierarchical, GitOps-driven approach ensures consistency and scalability for SLIM deployments across many clusters. By treating SLIM as a managed add-on under a multi-cluster controller like Sveltos, we delegate policy enforcement, lifecycle management, and drift correction to an automated system, freeing administrators to focus on higher-level operations.

[Tehsmash]

I think before we introduce something like Sveltos I think we can lay the foundation for multi-cluster through simple GitOps / ArgoCD, for example for our project we currently using a git repo to manage the deployment of SLIM + our agents across two clusters, and we could use that to relatively easily manage Spire / the SLIM control plane, as long as it supports a GitOps approach (either through a controller + CRDs, or even just a config map / secret as a declarative source of routes / subscriptions etc).

Without support for the GitOps in the control plane component, there is the option to do something today using post-deploy scripts in K8s, essentially deploy the control plane pod fresh and then after its running K8s can run a script to use the control API to apply all the routes/subscriptions etc, but this is not stateful and need the controller to be destroyed and recreated on each change.