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Fabric Configuration

Overview

The fab.yaml file is the configuration file for the fabric. It supplies the configuration of the users, their credentials, logging, telemetry, and other non wiring related settings. The fab.yaml file is composed of multiple YAML documents inside of a single file. Per the YAML spec 3 hyphens (---) on a single line separate the end of one document from the beginning of the next. There are two YAML documents in the fab.yaml file. For more information about how to use hhfab init, run hhfab init --help.

Typical HHFAB workflows

HHFAB for VLAB

For a VLAB user, the typical workflow with hhfab is:

  1. hhfab init --dev
  2. hhfab vlab gen
  3. hhfab vlab up

The above workflow will get a user up and running with a spine-leaf VLAB.

HHFAB for Physical Machines

It's possible to start from scratch:

  1. hhfab init (see different flags to cusomize initial configuration)
  2. Adjust the fab.yaml file to your needs
  3. hhfab validate
  4. hhfab build

Or import existing config and wiring files:

  1. hhfab init -c fab.yaml -w wiring-file.yaml -w extra-wiring-file.yaml
  2. hhfab validate
  3. hhfab build

After the above workflow a user will have a .img file suitable for installing the control node, then bringing up the switches which comprise the fabric.

Fab.yaml

Configure control node and switch users

Configuring control node and switch users is done either passing --default-password-hash to hhfab init or editing the resulting fab.yaml file emitted by hhfab init. You can specify users to be configured on the control node(s) and switches in the following format:

spec:
    config:
      control:
        defaultUser: # user 'core' on all control nodes
          password: "hashhashhashhashhash" # password hash
          authorizedKeys:
            - "ssh-ed25519 SecREKeyJumblE"

        fabric:
          mode: spine-leaf # "spine-leaf" or "collapsed-core"

          defaultSwitchUsers:
            admin: # at least one user with name 'admin' and role 'admin'
              role: admin
              #password: "$5$8nAYPGcl4..." # password hash
              #authorizedKeys: # optional SSH authorized keys
              #  - "ssh-ed25519 AAAAC3Nza..."
            op: # optional read-only user
              role: operator
              #password: "$5$8nAYPGcl4..." # password hash
              #authorizedKeys: # optional SSH authorized keys
              #  - "ssh-ed25519 AAAAC3Nza..."

Control node(s) user is always named core.

The role of the user,operator is read-only access to sonic-cli command on the switches. In order to avoid conflicts, do not use the following usernames: operator,hhagent,netops.

NTP and DHCP

The control node uses public ntp servers from cloudflare and google by default. The control node runs a dhcp server on the management network. See the example file.

Control Node

The control node is the host that manages all the switches, runs k3s, and serves images. This is the YAML document configure the control node: 

apiVersion: fabricator.githedgehog.com/v1beta1
kind: ControlNode
metadata:
  name: control-1
  namespace: fab
spec:
  bootstrap:
   disk: "/dev/sda" # disk to install OS on, e.g. "sda" or "nvme0n1"
  external:
    interface: enp2s0 # interface for external
    ip: dhcp # IP address for external interface
  management:
    interface: enp2s1 # interface for management

# Currently only one ControlNode is supported
The management interface is for the control node to manage the fabric switches, not end-user management of the control node. For end-user management of the control node specify the external interface name.

Forward switch metrics and logs

There is an option to enable Grafana Alloy on all switches to forward metrics and logs to the configured targets using Prometheus Remote-Write API and Loki API. If those APIs are available from Control Node(s), but not from the switches, it's possible to enable HTTP Proxy on Control Node(s) that will be used by Grafana Alloy running on the switches to access the configured targets. It could be done by passing --control-proxy=true to hhfab init.

Metrics includes port speeds, counters, errors, operational status, transceivers, fans, power supplies, temperature sensors, BGP neighbors, LLDP neighbors, and more. Logs include agent logs.

Configuring the exporters and targets is currently only possible by editing the fab.yaml configuration file. An example configuration is provided below:

spec:
  config:
      ...
      defaultAlloyConfig:
        agentScrapeIntervalSeconds: 120
        unixScrapeIntervalSeconds: 120
        unixExporterEnabled: true
        lokiTargets:
          grafana_cloud: # target name, multiple targets can be configured
              basicAuth: # optional
                  password: "<password>"
                  username: "<username>"
              labels: # labels to be added to all logs
                  env: env-1
              url: https://logs-prod-021.grafana.net/loki/api/v1/push
              useControlProxy: true # if the Loki API is not available from the switches directly, use the Control Node as a proxy
        prometheusTargets:
          grafana_cloud: # target name, multiple targets can be configured
              basicAuth: # optional
                  password: "<password>"
                  username: "<username>"
              labels: # labels to be added to all metrics
                  env: env-1
              sendIntervalSeconds: 120
              url: https://prometheus-prod-36-prod-us-west-0.grafana.net/api/prom/push
              useControlProxy: true # if the Loki API is not available from the switches directly, use the Control Node as a proxy
              unixExporterCollectors: # list of node-exporter collectors to enable, https://grafana.com/docs/alloy/latest/reference/components/prometheus.exporter.unix/#collectors-list
                  - cpu
                  - filesystem
                  - loadavg
                  - meminfo
              collectSyslogEnabled: true # collect /var/log/syslog on switches and forward to the lokiTargets

For additional options, see the AlloyConfig struct in Fabric repo.

Complete Example File

apiVersion: fabricator.githedgehog.com/v1beta1
kind: Fabricator
metadata:
  name: default
  namespace: fab
spec:
  config:
    control:
      tlsSAN: # IPs and DNS names to access API
        - "customer.site.io"

      ntpServers:
      - time.cloudflare.com
      - time1.google.com

      defaultUser: # user 'core' on all control nodes
        password: "hash..." # password hash
        authorizedKeys:
          - "ssh-ed25519 hash..."

    fabric:
      mode: spine-leaf # "spine-leaf" or "collapsed-core"
      includeONIE: true
      defaultSwitchUsers:
        admin: # at least one user with name 'admin' and role 'admin'
          role: admin
          password: "hash..." # password hash
          authorizedKeys:
            - "ssh-ed25519 hash..."
        op: # optional read-only user
          role: operator
          password: "hash..." # password hash
          authorizedKeys:
            - "ssh-ed25519 hash..."

      defaultAlloyConfig:
        agentScrapeIntervalSeconds: 120
        unixScrapeIntervalSeconds: 120
        unixExporterEnabled: true
        collectSyslogEnabled: true
        lokiTargets:
          lab:
            url: http://url.io:3100/loki/api/v1/push
            useControlProxy: true
            labels:
              descriptive: name
        prometheusTargets:
          lab:
            url: http://url.io:9100/api/v1/push
            useControlProxy: true
            labels:
              descriptive: name
            sendIntervalSeconds: 120

---
apiVersion: fabricator.githedgehog.com/v1beta1
kind: ControlNode
metadata:
  name: control-1
  namespace: fab
spec:
  bootstrap:
    disk: "/dev/sda" # disk to install OS on, e.g. "sda" or "nvme0n1"
  external:
    interface: eno2 # interface for external
    ip: dhcp # IP address for external interface
  management:
    interface: eno1

# Currently only one ControlNode is supported
Last update: October 24, 2024
Created: January 22, 2024