What is gNMI Collector ?

 A gNMI (gRPC Network Management Interface) collector is a software component, acting as a gNMI client, that interacts with network devices (gNMI servers/targets) to subscribe to, request, and receive streaming telemetry and configuration data. [1, 2]

It is designed to handle high-velocity network data, acting as a central node in modern, model-driven, and open-source observability stacks (e.g., used with OpenConfig, Prometheus, or InfluxDB)

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Core Functions of a gNMI Collector

• Subscribes to Data: Uses the gNMI RPC to request real-time updates for operational state or configuration data from network devices (e.g., switches, routers).
• Maintains Connectivity: Establishes and maintains persistent gRPC sessions (often over TLS) with multiple devices simultaneously.
• Data Transformation: Often includes capabilities to parse, normalize, and manipulate raw telemetry data (e.g., changing JSON formats or converting data types) before sending it to a database.
• Output Routing: Forwards the collected data to various destinations, such as time-series databases (InfluxDB), streaming platforms (Kafka), or monitoring systems (Prometheus).
• Manages Subscription Modes: Supports various telemetry collection modes:
• STREAM: Continuous streaming of updates (sample or on-change).
• POLL: Periodic snapshots triggered by the collector.
• ONCE: A single snapshot of data. [1, 3, 7, 8, 9, 10]

Typical Use Case: gNMIc [11, 12]

A prominent example is gNMIc, an open-source tool that functions as a feature-rich CLI client and collector.

1. Ingest: It connects to network devices to subscribe to YANG-modeled telemetry.
2. Process: It transforms the data into a usable format.
3. Export: It pushes the data to Time Series Databases (TSDB) like InfluxDB or Prometheus for visualization in Grafana. [7, 8, 10, 13, 14]

Key Benefits

• Real-time Visibility: Provides near-instant updates on network state changes.
• Vendor Agnostic: Works with any device that supports the OpenConfig gNMI specification.
• High Performance: Uses gRPC/HTTP/2 and Protobuf for efficient, low-latency transmission. [1, 3, 4, 15, 16]

Examples of gNMI collectors include gNMIc, Telegraf (with the gNMI plugin), and Pipeline (Cisco's collector). [7, 17, 18]