pyprom-exporters 0.0.1

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Python Prometheus Exporters for IoT Devices

Python Prometheus Exporters (pyprom-exporters) is a small Python package that exposes Prometheus metrics for IoT / smart-home devices.

The current concrete exporter targets TP-Link Tapo smart plugs via python-kasa.

What It Does

• Discovers Tapo devices on your LAN (UDP broadcast) and/or monitors an explicit list of device IPs.
• Periodically updates device state on a background asyncio loop, with retries and backoff.
• Exposes cached metrics via a Prometheus HTTP endpoint (scrapes do not talk to devices).

How It Works

• prom-exporter starts an asyncio event loop on a background thread.
• The Tapo exporter runs discovery, performs an initial update pass, then starts periodic background updates.
• Prometheus scrapes call the exporter collect() method, which returns cached metric objects. Device I/O happens in the background.

This means the exporter updates devices on its own schedule, not on Prometheus' scrape schedule. To reduce device/network traffic, set exporters.tapo.prometheus_options.refresh_interval to match your Prometheus scrape interval (or higher).

The tradeoff is intentional:

• Background polling keeps scrape latency low and predictable.
• Scrapes do not block on device updates and are resilient to transient device timeouts.

Project Layout

• src/pyprom_exporters/prom_exporter.py: CLI entry point and runtime wiring.
• src/pyprom_exporters/config.py: OmegaConf-compatible dataclass configuration models.
• src/pyprom_exporters/exporters/tapo.py: Tapo smart plug exporter implementation.
• src/pyprom_exporters/task_collector/async_task_collector.py: async retry runner used for device updates.
• tests/: unit tests for config/exporter behavior.

Requirements

• Python 3.11+ (uses asyncio.TaskGroup).
• Network reachability from the exporter host to the devices.
• Tapo credentials (provided via env vars or CLI; never written to config.yaml).

Installation

This repo is set up to use uv and a checked-in uv.lock.

# Development (includes the dev dependency group by default)
uv sync --frozen --group tapo

# Minimal runtime environment
uv sync --frozen --no-dev --group tapo

If you use pip, you must also install python-kasa (it is not part of the base dependencies).

pip install .
pip install python-kasa

Running

1. Provide credentials (default env keys):

export TP_LINK_USERNAME="[e-mail]"
export TP_LINK_PASSWORD="your-password"

1. Run the exporter:

uv run prom-exporter \
  --prometheus-port 8090 \
  --tapo-plug-devices 10.10.2.100,10.10.2.101

You can also reduce log verbosity:

uv run prom-exporter --log-level WARNING

1. Scrape metrics:

• http://localhost:8090/metrics

Environment Variable Overrides

The runtime supports a few convenience overrides:

• Precedence: CLI flags override env vars; env vars override config.yaml.
• PYPROM_EXPORTERS_LOG_LEVEL (or LOG_LEVEL): overrides log_level.
• PROMETHEUS_PORT: overrides prometheus_port.
• TAPO_PLUG_DEVICES: overrides exporters.tapo.devices (space or comma-separated).
• TAPO_USERNAME / TAPO_PASSWORD: overrides credentials directly.

Configuration (config.yaml)

prom-exporter reads config.yaml from the working directory.

• If config.yaml does not exist, it writes one with defaults.
• If config.yaml exists, it writes back the merged configuration on startup so defaults are explicit.
• Credentials are always scrubbed from the written YAML; provide them via env vars or CLI.
• write_non_default_config: true writes only values that differ from defaults.

Important fields:

• log_level: root logging level for the process.
• prometheus_port: exporter listen port.
• exporters.tapo.devices: list of device IPs to monitor (used in addition to discovery).
• exporters.tapo.prometheus_options.refresh_interval: background update interval (seconds) and per-device minimum update interval.
• exporters.tapo.discovery_options.*: discovery parameters passed to python-kasa.
• exporters.tapo.discovery_options.tapo_username_env_key / tapo_password_env_key: env var names used to populate python-kasa Credentials by default.
• exporters.tapo.supported_device_families: currently only PLUG.
• exporters.tapo.per_device_family_metrics.plug: plug metrics to export.

Discovery note: broadcast discovery generally does not work across VLAN boundaries. If your devices are on a separate IoT VLAN, set exporters.tapo.devices (or use --tapo-plug-devices) to the device IPs.

Metrics

The Tapo plug exporter currently emits:

• tapo_discovered_devices: number of discovered devices (gauge).
• current_consumption{host,alias}: watts (gauge).
• current_voltage{host,alias}: volts (gauge).
• current_current{host,alias}: amps (gauge).
• current_consumption_today{host,alias}: watt-hours (gauge).
• current_month_consumption{host,alias}: watt-hours (gauge).
• current_rssi{host,alias}: RSSI value reported by the device (gauge).

Only devices that report the current_consumption feature are exported.

Prometheus Scrape Config

Example prometheus.yml:

scrape_configs:
  - job_name: pyprom-exporters
    static_configs:
      - targets: ["<exporter-host>:8090"]

Docker

Build:

docker build -t pyprom-exporters:latest .

Run:

docker run --rm \
  -e TP_LINK_USERNAME="[e-mail]" \
  -e TP_LINK_PASSWORD="your-password" \
  -e PROMETHEUS_PORT=8090 \
  -e TAPO_PLUG_DEVICES="10.10.2.100,10.10.2.101" \
  -p 8090:8090 \
  pyprom-exporters:latest

The container entrypoint runs uv run prom-exporter and forwards PROMETHEUS_PORT and TAPO_PLUG_DEVICES into CLI flags.

Troubleshooting

• No devices discovered:
  • Set exporters.tapo.devices (or use --tapo-plug-devices) instead of relying on broadcast discovery.
  • Check firewall rules and IoT VLAN routing.
• Metrics are missing for a device:
  • The exporter skips devices that do not report a current_consumption feature.
• Authentication failures:
  • Ensure TP_LINK_USERNAME / TP_LINK_PASSWORD (or TAPO_USERNAME / TAPO_PASSWORD) are set.

Development

# pytest - for tests
uv run pytest
# ruff - for linting and formatting
uv run ruff check .
# format with ruff (or your editor integration)
uv run ruff format .
# pre-commit - for running all configured pre-commit hooks (ruff, isort, etc.)
uv run pre-commit run --all-files

License

Apache-2.0 (see LICENSE).