gNMIc Collector

gNMIc is the telemetry collector that subscribes to gNMI streams from Nokia devices and exports metrics to Prometheus.

Overview

gNMIc (gRPC Network Management Interface client) is an open-source tool from OpenConfig that:

Establishes gRPC connections to network devices
Subscribes to telemetry data using gNMI protocol
Processes and transforms streaming data
Exports metrics in multiple formats (Prometheus, InfluxDB, Kafka, etc.)

Lab Configuration:

Container: gnmic
Management IP: 10.77.1.12
Metrics Port: 9273
Config File: configs/gnmic/config.yml

Configuration File Structure

The gNMIc configuration consists of four main sections:

# Global device credentials
username: admin
password: admin
port: 57400
timeout: 10s

# Auto-discovery via Docker
loader:
  type: docker
  # ...

# Telemetry subscriptions
subscriptions:
  # ...

# Prometheus output
outputs:
  prom:
    type: prometheus
    # ...

Auto-Discovery with Docker Loader

The lab uses Docker auto-discovery to automatically find and configure Nokia devices:

loader:
  type: docker
  address: unix:///var/run/docker.sock
  filters:
    # ─── SR Linux nodes ────────────────────────────────
    - containers:
        - label: clab-node-kind=nokia_srlinux
      network:
        label: containerlab
      port: "57400"
      template: |
        name: {{ index .Labels "clab-node-name" }}
      config:
        username: admin
        password: lab123
        skip-verify: true
        encoding: proto
        subscriptions:
          - srl_platform
          - srl_apps
          - srl_if_stats
          - srl_if_lag_stats
          - srl_net_instance
          - srl_bgp_stats
          - srl_event_handler_stats

    # ─── SR OS simulator nodes ─────────────────────────
    - containers:
        - label: clab-node-kind=nokia_srsim
      network:
        label: containerlab
      port: "57400"
      template: |
        name: {{ index .Labels "clab-node-name" }}
      config:
        username: admin
        password: lab123
        insecure: true
        encoding: json
        subscriptions:
          - sros_ports_stats
          - sros_router_bgp
          - sros_router_interface
          - sros_router_isis
          - sros_router_route_table
          - sros_system
          - sros_service_stats
          - sros_temperature_stats
          - sros_fan_stats
          - sros_ludb
          - sros_vpls_sap_all

The loader automatically discovers all Containerlab nodes labeled with clab-node-kind=nokia_srlinux or clab-node-kind=nokia_srsim and applies the appropriate configuration.

Key Loader Parameters

Parameter	Description
`type: docker`	Use Docker container discovery
`address`	Docker socket path
`filters`	Container selection criteria
`label`	Match containers by label
`port`	gNMI port (57400 for Nokia)
`encoding`	`proto` for SR Linux, `json` for SROS

Telemetry Subscriptions

Subscriptions define what data to collect and how frequently.

SROS Subscriptions

Port Statistics
System Metrics
BNG Sessions
Routing Protocols

sros_ports_stats:
  paths:
    - /state/port/oper-state
    - /state/port/statistics/
    - /state/port/ethernet/statistics/
  stream-mode: sample
  sample-interval: 5s

Collects interface operational state and traffic statistics every 5 seconds.

sros_system:
  paths:
    - /state/system/cpu[sample-period=1]
    - /state/system/memory-pools/
  stream-mode: sample
  sample-interval: 5s

Monitors CPU utilization (1-second sampling) and memory pool usage.

sros_ludb:
  paths:
    - /state/subscriber-mgmt/local-user-db[name=*]
    - /state/subscriber-mgmt/local-user-db[name=*]/ipoe
  stream-mode: sample
  sample-interval: 5s

Tracks BNG local user database and IPoE session counts.

sros_router_bgp:
  paths:
    - /state/router/bgp/statistics/
    - /state/router/bgp/statistics/routes-per-family/
    - /state/router/bgp/neighbor/statistics/
  stream-mode: sample
  sample-interval: 5s

Captures BGP statistics, route counts per address family, and neighbor metrics.

SR Linux Subscriptions

Platform Metrics
Interface Stats
BGP Statistics

srl_platform:
  paths:
    - /platform/control[slot=*]/cpu[index=all]/total
    - /platform/control[slot=*]/memory
  mode: stream
  stream-mode: sample
  sample-interval: 5s

Monitors CPU and memory usage for all control slots.

srl_if_stats:
  paths:
    - /interface[name=ethernet-1/*]/statistics
    - /interface[name=*]/subinterface[index=*]/statistics/
    - /interface[name=ethernet-1/*]/oper-state
    - /interface[name=ethernet-1/*]/traffic-rate
  mode: stream
  stream-mode: sample
  sample-interval: 5s

Collects interface statistics, operational state, and traffic rates.

srl_bgp_stats:
  paths:
    - /network-instance[name=*]/protocols/bgp/statistics
    - /network-instance[name=*]/protocols/bgp/group[group-name=*]/statistics
  mode: stream
  stream-mode: sample
  sample-interval: 5s

Tracks BGP protocol statistics per network instance and peer group.

Subscription Parameters

Parameter	Description	Example
`paths`	YANG paths to subscribe to	`/state/port/statistics/`
`mode`	Subscription mode	`stream`
`stream-mode`	How data is sent	`sample` (periodic) or `on-change`
`sample-interval`	Polling frequency	`5s` (5 seconds)

Stream modes:

sample: Send updates at regular intervals (5s in this lab)
on-change: Send updates only when values change (not used in this lab)

Data Processing Pipeline

gNMIc applies processors to transform telemetry data before exporting:

1. Trim SROS Prefixes

processors:
  trim-sros-prefixes:
    event-strings:
      value-names:
        - "^/state/.*"
      transforms:
        - trim-prefix:
            apply-on: "name"
            prefix: "/state"

Removes /state prefix from metric names:

/state/port/statistics/in-packets → /port/statistics/in-packets

2. Extract Labels

add-labels:
  event-extract-tags:
    value-names:
      - /router/route-table/unicast/(?P<family>[a-zA-Z0-9-_:]+)/statistics/(?P<protocol>[a-zA-Z0-9-_:]+)/([a-zA-Z0-9-_:]+)
      - /router/bgp/statistics/routes-per-family/(?P<family>[a-zA-Z0-9-_:]+)/([a-zA-Z0-9-_:]+)

Extracts labels from paths using regex:

Path: /router/route-table/unicast/ipv4/statistics/bgp/active-routes
Labels: {family="ipv4", protocol="bgp"}

3. Convert State Values

up-down-map:
  event-strings:
    value-names:
      - oper-state
    transforms:
      - replace:
          apply-on: "value"
          old: "up"
          new: "1"
      - replace:
          apply-on: "value"
          old: "down"
          new: "0"

Converts operational states to numeric values for Prometheus:

up → 1
down → 0

4. Group by Interface

group-by-interface:
  event-group-by:
    tags:
      - interface_name

Groups metrics by interface name for better organization.

Prometheus Export

The final step exports processed metrics in Prometheus format:

outputs:
  prom:
    type: prometheus
    listen: :9273
    path: /metrics
    export-timestamps: true
    strings-as-labels: true
    debug: false
    event-processors:
      - trim-sros-prefixes
      - add-labels
      - trim-regex
      - group-by-interface
      - up-down-map

Export Parameters

Parameter	Value	Description
`listen`	`:9273`	Port for Prometheus scraping
`path`	`/metrics`	HTTP endpoint path
`export-timestamps`	`true`	Include metric timestamps
`strings-as-labels`	`true`	Convert string values to labels
`event-processors`	(list)	Processing pipeline order

Example Metrics Output

# HELP port_statistics_in_packets Port ingress packet count
# TYPE port_statistics_in_packets counter
port_statistics_in_packets{device="bng1",port_id="1/1/c1/1"} 1234567

# HELP system_cpu CPU utilization percentage
# TYPE system_cpu gauge
system_cpu{device="bng1",sample_period="1"} 23.5

# HELP port_oper_state Port operational state (1=up, 0=down)
# TYPE port_oper_state gauge
port_oper_state{device="bng1",port_id="1/1/c1/1"} 1

Verify gNMIc Operation

Check Container Status

# Verify gNMIc is running
sudo docker ps | grep gnmic

# Expected: Container shows as "Up"

View gNMIc Logs

# Follow live logs
sudo docker logs -f gnmic

# Look for successful subscriptions:
# "msg"="subscription initialized" "target"="bng1"
# "msg"="subscription initialized" "target"="bng2"

Test Metrics Endpoint

# Fetch metrics from gNMIc
curl http://localhost:9273/metrics

# Or from inside another container
sudo docker exec prometheus wget -O- http://gnmic:9273/metrics | head -20

Check Active Subscriptions

# View configuration
sudo docker exec gnmic cat /gnmic-config.yml

# Check discovered targets
sudo docker exec gnmic gnmic --config /gnmic-config.yml get --target bng1 --path /

Troubleshooting gNMI Connections

Connection refused errors

Problem: connection refused or context deadline exceededSolutions:

Verify device is running: sudo docker ps | grep bng1

Check gNMI port is open:

sudo docker exec gnmic telnet bng1 57400

Confirm credentials are correct in config.yml
Check device gNMI is enabled (should be by default)

Authentication failures

Problem: rpc error: code = UnauthenticatedSolutions:

Verify credentials in loader config:
```
username: admin
password: lab123
```
Check device admin password hasn’t changed

Try connecting manually:

gnmic -a bng1:57400 -u admin -p lab123 --insecure capabilities

No metrics exported

Problem: /metrics endpoint returns empty or no dataSolutions:

Check subscriptions are active in logs

Verify devices are sending data:

sudo docker logs gnmic | grep "received"

Test a specific subscription:

gnmic -a bng1:57400 -u admin -p lab123 --insecure \
  subscribe --path /state/system/cpu

Check processor configuration isn’t filtering all data

High CPU usage

Problem: gNMIc container consuming excessive CPUSolutions:

Reduce subscription frequency:
```
sample-interval: 10s  # Instead of 5s
```
Limit subscription paths to essential metrics only
Disable debug logging:
```
outputs:
  prom:
    debug: false
```

Custom Subscription Examples

Add New SROS Subscription

# Add to subscriptions section
sros_vpls_sap_stats:
  paths:
    - /state/service/vpls[service-name=*]/sap[sap-id=*]/statistics
  stream-mode: sample
  sample-interval: 10s

# Add to loader config for SROS nodes
subscriptions:
  - sros_ports_stats
  - sros_system
  - sros_vpls_sap_stats  # New subscription

Monitor Specific Interfaces Only

# Instead of all interfaces
srl_if_stats:
  paths:
    - /interface[name=ethernet-1/1]/statistics
    - /interface[name=ethernet-1/2]/statistics
  mode: stream
  stream-mode: sample
  sample-interval: 5s

Increase Sampling Frequency

# For critical metrics, use faster sampling
sros_critical_ports:
  paths:
    - /state/port[port-id=1/1/c1/1]/statistics/
  stream-mode: sample
  sample-interval: 1s  # Every second

Configuration Best Practices

Performance Tips:

Keep sample-interval at 5s or higher to avoid overwhelming devices
Use specific paths instead of wildcards when possible
Limit subscriptions to metrics you actually need
Use processors to reduce cardinality (unique label combinations)
Monitor gNMIc CPU and memory usage

Security Considerations:

Change default credentials in production
Use TLS certificates instead of skip-verify: true
Limit Docker socket access to trusted containers
Use RBAC for gNMI access control on devices

Next Steps

Prometheus Setup

Configure Prometheus to scrape gNMIc metrics

Available Metrics

Browse the complete metrics catalog

​gNMIc Collector

​Overview

​Configuration File Structure

​Auto-Discovery with Docker Loader

​Key Loader Parameters

​Telemetry Subscriptions

​SROS Subscriptions

​SR Linux Subscriptions

​Subscription Parameters

​Data Processing Pipeline

​1. Trim SROS Prefixes

​2. Extract Labels

​3. Convert State Values

​4. Group by Interface

​Prometheus Export

​Export Parameters

​Example Metrics Output

​Verify gNMIc Operation

​Check Container Status

​View gNMIc Logs

​Test Metrics Endpoint

​Check Active Subscriptions

​Troubleshooting gNMI Connections

​Custom Subscription Examples

​Add New SROS Subscription

​Monitor Specific Interfaces Only

​Increase Sampling Frequency

​Configuration Best Practices

​Next Steps

Prometheus Setup

Available Metrics

gNMIc Collector

Overview

Configuration File Structure

Auto-Discovery with Docker Loader

Key Loader Parameters

Telemetry Subscriptions

SROS Subscriptions

SR Linux Subscriptions

Subscription Parameters

Data Processing Pipeline

1. Trim SROS Prefixes

2. Extract Labels

3. Convert State Values

4. Group by Interface

Prometheus Export

Export Parameters

Example Metrics Output

Verify gNMIc Operation

Check Container Status

View gNMIc Logs

Test Metrics Endpoint

Check Active Subscriptions

Troubleshooting gNMI Connections

Custom Subscription Examples

Add New SROS Subscription

Monitor Specific Interfaces Only

Increase Sampling Frequency

Configuration Best Practices

Next Steps