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Resource files

Every device type has a directory under go/simulator/resources/ containing one or more JSON files. At startup, resources.go loads and caches every *.json file in each directory, merging the snmp, ssh, and (optionally) api sections. There are currently 379 JSON files across 28 device-type directories.

OIDs in the snmp section may be written with or without a leading dot — the loader normalises them to the net-snmp convention (.1.3.6.1…) at startup.

JSON schema​

Each file is a JSON object with up to three top-level keys:

{
  "snmp": [
    {
      "oid": ".1.3.6.1.2.1.1.1.0",
      "response": "Cisco IOS Software, Router Version 15.1"
    }
  ],
  "ssh": [
    {
      "command": "show version",
      "response": "Cisco IOS Software, Router Version 15.1\nDevice Simulator v1.0"
    }
  ],
  "api": [
    {
      "method": "GET",
      "path": "/api/v1/system",
      "status": 200,
      "response": "{\"name\": \"device-01\", \"status\": \"healthy\"}"
    }
  ]
}

The api section is optional and used primarily for storage device simulation — see Device types → Storage systems.

Directory layout​

Each device type directory is split by concern so the files stay small and reviewable. The loader is directory-based: any *.json file inside is merged, so split files however you like.

A typical naming convention:

go/simulator/resources/asr9k/
├── asr9k_snmp_system.json         # MIB-II system group
├── asr9k_snmp_interfaces.json     # IF-MIB / IF-MIB-HC
├── asr9k_snmp_entity.json         # Entity MIB
├── asr9k_snmp_vendor.json         # vendor-specific OIDs
├── asr9k_ssh.json                 # SSH command/response
└── asr9k_api.json                 # (storage devices only)

Browse go/simulator/resources/asr9k/ for a representative example.

Round-robin and category selection​

The REST API's /api/v1/devices endpoint supports round_robin: true (spread device creation across every registered resource file) and category: "<name>" (restrict to a single category — e.g. "GPU Servers"). The catalog of categories and per-category device lists lives in Device types.

Dynamic values​

Not every OID is static. The following are computed at query time regardless of what the resource files contain:

  • CPU, memory, temperature — cycle through a 100-point sine-wave pattern per device. See SNMP reference → Dynamic metrics.
  • HC interface counters (ifHCInOctets / ifHCOutOctets) — computed analytically as monotonically increasing Counter64 values, phase-offset per interface. See SNMP reference → HC counters.
  • Interface state — ifAdminStatus / ifOperStatus depend on -if-scenario.
  • GPU metrics — per-GPU utilization, VRAM, temp, power, fan, clocks. See GPU simulation.