Architecture Decision Records (ADR) Table¶

This document provides a comprehensive overview of all architectural decisions made for the RH OVE multi-cluster ecosystem.

ADR Summary Table¶

Detailed ADR Information¶

ADR-001: Multi-Cluster Architecture Pattern¶

Key Components: - Management Cluster: RHACM, ArgoCD Hub, RHACS, Federated Prometheus, Centralized logging, Rubrik backup management - Application Clusters: Production (HA, performance-optimized), Staging (production-like), Development (resource-optimized) - Network Architecture: Dedicated segments per cluster, VPN/private connectivity, zero-trust principles

Benefits: Separation of concerns, horizontal scalability, security isolation, operational efficiency, fault isolation, resource optimization

Trade-offs: Increased network complexity, additional operational overhead, potential data sync challenges

ADR-002: GitOps with ArgoCD Hub Architecture¶

Key Components: - ArgoCD Hub: Centralized instance in management cluster with HA (3 replicas) - ArgoCD Agents: Lightweight agents in application clusters - Repository Structure: Clusters, applications (base/overlays), infrastructure (networking/storage/monitoring) - Application of Applications Pattern: Root ArgoCD app manages cluster-specific applications

Benefits: Declarative configuration, complete audit trail, pull-based security, consistency, easy rollbacks, self-healing

Trade-offs: Learning curve for GitOps workflows, Git repository complexity, network dependencies, secret management complexity

ADR-003: Namespace-Based Cluster Topology¶

Key Components: - Naming Convention: {app-name}-{environment} (e.g., app-web-prod, app-database-staging) - Standard Templates: Namespace with labels, ResourceQuota, LimitRange, NetworkPolicies - Cross-Namespace Communication: Controlled via NetworkPolicies with explicit allow rules - RBAC Integration: Namespace-level roles aligned with application teams

Benefits: Strong isolation, simplified RBAC, clear resource attribution, network microsegmentation, operational clarity, compliance alignment

Trade-offs: Initial complexity in planning boundaries, cross-app dependency management, shared services challenges

ADR-004: Admission Controller Strategy¶

Key Components: - OpenShift Built-in: Security Context Constraints, RBAC enforcement, quotas and limits - KubeVirt Webhooks: Validation and mutation webhooks for VM specifications - Kyverno Policies: Configuration validation, resource constraints, dynamic policy application

Benefits: Centralized policy management, dynamic policy application, security enforcement, misconfiguration prevention, extensibility

Trade-offs: Complex rule management, performance overhead, learning curve for policy authors

ADR-005: Cilium CNI with Multus Multi-Network Strategy¶

Key Components: - Cilium Features: eBPF performance, identity-aware security, L7 security, service mesh capabilities, WireGuard encryption - Multus Integration: Multi-network support, legacy network integration, SR-IOV for high performance, network segmentation - Hubble Observability: Network flow monitoring, policy violation detection, security auditing - NetworkAttachmentDefinitions: Management, storage, and data networks with VLAN support

Benefits: Superior eBPF performance (10-100x better than iptables), identity-aware policies, L7 security without sidecars, deep observability, multi-network support

Trade-offs: Learning curve for eBPF concepts, debugging complexity, higher memory usage, potential compatibility issues

ADR-006: Backup Strategy for RH OVE Ecosystem¶

Key Components: - Rubrik Management: Centralized in management cluster with unified policy management - Backup Architecture: Management cluster (Rubrik node), Application clusters (Edge devices, agents), Cloud archive (long-term retention) - Policy Configuration: Daily backups (24h RPO), weekly full with daily incrementals, AES-256 encryption, cloud replication - Compliance: GDPR, HIPAA, SOC 2 alignment with audit trails and access control

Benefits: Unified management, policy-driven, deduplication/compression, cloud integration, application consistency

Trade-offs: Higher upfront costs than open-source alternatives, training requirements for administrators

ADR-007: Monitoring Strategy for RH OVE Ecosystem¶

Key Components: - Prometheus/Grafana: Scalable metrics collection, customizable dashboards, real-time metrics, integrated alerting - Dynatrace: Full-stack monitoring, AI-powered analytics, cloud-native support, unified observability - Hubble: eBPF-powered network insights, high throughput flow capture, Cilium integration - Integration: Federated Prometheus (3 replicas, 500Gi storage), OAuth SSO, automated tagging

Benefits: Operational efficiency with reduced MTTR, proactive performance management, unified observability across clusters

Trade-offs: Integration complexity, resource overhead, training requirements for multiple tools

ADR-008: Identity and Access Management (IAM) Strategy¶

Key Components: - Keycloak (Red Hat SSO): Primary OIDC provider with LDAP/AD integration, MFA support, group-based access control - Dex OIDC Proxy: Service authentication across clusters with static client configuration - OpenShift OAuth Integration: Native cluster authentication with OIDC claims mapping - RBAC Integration: Kubernetes-native authorization with group-based role assignments - Service Account Management: Time-limited tokens with projected volumes and automated lifecycle

Benefits: Centralized identity management, single sign-on across all services, enterprise LDAP/AD integration, MFA enforcement, zero trust security, complete audit trails, compliance ready (SOC 2, GDPR, HIPAA)

Trade-offs: Initial setup complexity, additional infrastructure dependencies, OIDC/Keycloak learning curve, identity provider availability critical, token lifecycle management complexity

Cross-ADR Dependencies¶

graph TD
    ADR001[ADR-001: Multi-Cluster] --> ADR002[ADR-002: GitOps ArgoCD]
    ADR001 --> ADR003[ADR-003: Namespace Topology]
    ADR001 --> ADR006[ADR-006: Backup Strategy]
    ADR001 --> ADR007[ADR-007: Monitoring]
    ADR001 --> ADR008[ADR-008: IAM Strategy]

    ADR003 --> ADR004[ADR-004: Admission Control]
    ADR003 --> ADR005[ADR-005: Network CNI]
    ADR003 --> ADR008

    ADR008 --> ADR002
    ADR008 --> ADR004
    ADR008 --> ADR007

    ADR005 --> ADR007
    ADR002 --> ADR004

    style ADR001 fill:#ff9999
    style ADR002 fill:#99ccff
    style ADR003 fill:#99ff99
    style ADR004 fill:#ffcc99
    style ADR005 fill:#cc99ff
    style ADR006 fill:#ffff99
    style ADR007 fill:#ff99cc
    style ADR008 fill:#99ffcc

Implementation Timeline¶

Detailed Phase Dependencies¶

gantt
    title ADR Implementation Timeline
    dateFormat  YYYY-MM-DD
    section Phase 1: Foundation
    ADR-001 Multi-Cluster     :done, foundation1, 2024-01-01, 4w
    ADR-003 Namespace Topology :done, foundation2, 2024-01-15, 3w

    section Phase 2: Identity
    ADR-008 IAM Strategy       :active, iam, after foundation1, 4w

    section Phase 3: GitOps
    ADR-002 GitOps ArgoCD      :gitops, after iam, 3w
    ADR-004 Admission Control  :admission, after iam, 3w

    section Phase 4: Network
    ADR-005 Network CNI        :network, after foundation2, 3w

    section Phase 5: Operations
    ADR-006 Backup Strategy    :backup, after gitops, 4w
    ADR-007 Monitoring         :monitoring, after network, 4w

Critical Path Analysis¶

Critical Dependencies: - ADR-008 (IAM) must be completed before GitOps and Admission Control implementation - ADR-003 (Namespace Topology) enables proper RBAC integration with IAM - ADR-007 (Monitoring) requires IAM integration for authentication and authorization - ADR-002 (GitOps) requires IAM for secure access control and audit trails

Parallel Implementation Opportunities: - ADR-005 (Network CNI) can be implemented in parallel with IAM setup - ADR-006 (Backup) and ADR-007 (Monitoring) can be implemented concurrently in final phase

This comprehensive table provides a complete overview of all architectural decisions, their relationships, and implementation considerations for the RH OVE multi-cluster ecosystem.