Architecture

Overview

The gNMIc Operator follows the Kubernetes operator pattern to manage gNMIc telemetry collectors. It watches Custom Resources and reconciles the actual state with the desired state.

Components

┌───────────────────────────────────────────────────────────────────────┐
│                         Kubernetes Cluster                            │
│                                                                       │
│  ┌─────────────────────────────────────────────────────────────────┐  │
│  │                    gNMIc Operator                               │  │
│  │                                                                 │  │
│  │  ┌─────────────────┐  ┌─────────────────┐  ┌─────────────────┐  │  │
│  │  │ Cluster         │  │ Pipeline        │  │ Other           │  │  │
│  │  │ Controller      │  │ Controller      │  │ Controllers     │  │  │
│  │  └─────────────────┘  └─────────────────┘  └─────────────────┘  │  │
│  └───────────┼────────────────────┼────────────────────────────────┘  │
│              │                    │                                   │
│              ▼                    ▼                                   │
│  ┌──────────────────────────────────────────────────────────────────┐ │
│  │                    Custom Resources                              │ │
│  │  ┌─────────┐ ┌──────────┐ ┌────────┐ ┌──────────────┐ ┌────────┐ │ │
│  │  │ Cluster │ │ Pipeline │ │ Target │ │ Subscription │ │ Output │ │ │
│  │  └─────────┘ └──────────┘ └────────┘ └──────────────┘ └────────┘ │ │
│  └──────────────────────────────────────────────────────────────────┘ │
│              │                                                        │
│              ▼                                                        │
│  ┌───────────────────────────────────────────────────────────────────┐│
│  │                    Managed Resources                              ││
│  │  ┌─────────────┐ ┌─────────────────┐ ┌───────────┐ ┌───────────┐  ││
│  │  │ StatefulSet │ │ Headless Service│ │ ConfigMap │ │ Services  │  ││
│  │  └─────────────┘ └─────────────────┘ └───────────┘ └───────────┘  ││
│  └───────────────────────────────────────────────────────────────────┘│
│              │                                                        │
│              ▼                                                        │
│  ┌───────────────────────────────────────────────────────────────────┐│
│  │                       gNMIc Pods                                  ││
│  │  ┌─────────────┐ ┌─────────────┐ ┌─────────────┐                  ││
│  │  │ gnmic-0     │ │ gnmic-1     │ │ gnmic-2     │                  ││
│  │  │ (targets    │ │ (targets    │ │ (targets    │                  ││
│  │  │  A, B, C)   │ │  D, E, F)   │ │  G, H, I)   │                  ││
│  │  └─────────────┘ └─────────────┘ └─────────────┘                  ││
│  └───────────────────────────────────────────────────────────────────┘│
└───────────────────────────────────────────────────────────────────────┘

Cluster Controller

The Cluster Controller is the primary controller responsible for:

1. Creating StatefulSets: Deploys gNMIc pods with intial config (REST API, TLS certs,…)
2. Managing Services: Creates headless service for pod DNS and Prometheus services for metrics
3. Building Configuration: Aggregates all pipelines and builds the gNMIc pods configuration
4. Distributing Targets: Assigns targets to pods
5. Applying Configuration: Sends configuration to each pod via REST API

Why StatefulSet?

The operator uses StatefulSets instead of Deployments for several reasons:

Stable pod identities enable:

• Direct communication: Operator can send config to specific pods
• Deterministic distribution: Same target goes to same pod index
• Ordered scaling: Predictable behavior when scaling up/down. Paired with a pod drain strategy, it enables controlled cluster scaling

Configuration Flow

Configuration flows from Custom Resources to gNMIc pods:

┌─────────┐  ┌──────────┐  ┌────────────┐  ┌────────┐
│ Targets │  │ Subs     │  │ Outputs    │  │ Inputs │
└────┬────┘  └────┬─────┘  └─────┬──────┘  └───┬────┘
     │            │              │             │
     └────────────┴──────────────┴─────────────┘
                        │
                        ▼
               ┌────────────────┐
               │    Pipeline    │
               │  (references)  │
               └───────┬────────┘
                       │
                       ▼
               ┌────────────────┐
               │ Plan Builder   │
               └───────┬────────┘
                       │
                       ▼
               ┌────────────────┐
               │ Target         │
               │ Distribution   │
               └───────┬────────┘
                       │
          ┌────────────┼────────────┐
          ▼            ▼            ▼
     ┌─────────┐  ┌─────────┐  ┌─────────┐
     │ Pod 0   │  │ Pod 1   │  │ Pod 2   │
     │ REST API│  │ REST API│  │ REST API│
     └─────────┘  └─────────┘  └─────────┘

Watches and Triggers

The Cluster Controller watches multiple resources to react to changes:

Changes to any watched resource trigger Cluster reconciliation, ensuring configuration stays synchronized.