PSU Energy AC - Gude - machine

What it does#

This metric provider reads the AC power draw of the whole machine from a Gude networked power meter over HTTP and converts it to energy.

The provider was originally built for the Gude Expert Power Control 1202, the same power meter used by the Blauer Engel team for their measurements. It is a slimmed-down version of the vendor’s check_gude.py.

Please note: This metric provider is no longer officially maintained by us. It remains in the code base for backwards compatibility.

Classname#

• PsuEnergyAcGudeMachineProvider

Metric Name#

• psu_energy_ac_gude_machine

Unit#

• uJ

Configuration#

The provider lives in the linux architecture section of the config.yml:

measurement:
  metric_providers:
    linux:
      psu_energy_ac_gude_machine:
        sampling_rate: 99

Config keys:

• sampling_rate — the interval in milliseconds. Passed to the script as -i.

Please see Configuration → for further info.

Input Parameters#

Rather than a compiled binary this provider runs the Python script check_gude_modified.py:

• args
  • -i: interval in milliseconds. The script exits with the usage text if it is not supplied.

./check_gude_modified.py -i 100

Output#

This metric provider prints to Stdout a continuous stream of data. The format of the data is as follows:

TIMESTAMP READING

Where:

• TIMESTAMP: Unix timestamp, in microseconds, taken after the HTTP request completed
• READING: The energy consumed over the elapsed interval in uJ

Any errors are printed to Stderr.

How it works#

The script loops for the lifetime of the run. On each iteration it:

1. Records a timestamp, sleeps for sampling_rate milliseconds.
2. Issues an HTTP GET to the power meter’s status.json endpoint with the components=0x4000 parameter, which asks the device for simple sensor values only.
3. Records a second timestamp and derives the effective elapsed time.
4. Reads the power value out of the JSON response and multiplies it by the elapsed time in microseconds, yielding microjoules.

Because the energy is derived from the effective elapsed time rather than the requested sleep time, network latency to the power meter does not silently inflate or deflate the energy total.

The power value is taken from a fixed position in the response document: sensor_values[0].values[0][4].v.

Caveats#

• The address of the power meter is hardcoded in check_gude_modified.py as http://192.168.178.32/status.json. There is no config option for it. You have to edit the script to point it at your device.
• TLS verification is disabled and no authentication is sent with the request. The provider expects the power meter to be reachable unauthenticated on a trusted local network.
• The provider does not ship a metric-provider-binary, but it also does not override the default system check, which expects one. Enabling this provider on a system where the check runs will therefore fail to find a binary to check. You can bypass the checks with --dev-no-system-checks.
• The position of the power value in the JSON is fixed. A device with a different sensor layout, or a firmware that reorders the document, will yield wrong values rather than an error.
• The reading measures the whole machine at the wall socket. It includes every other component and any other workload on the machine, not just the measured containers.
• The HTTP request has a 15 second timeout. At small sampling rates a slow device will therefore stall the loop rather than skip a sample.

Troubleshooting#

• Please supply -i to set sampling_rate in milliseconds — the script was called without -i.
• Connection errors / timeouts — the power meter is not reachable at the hardcoded IP. Verify that the device answers at http://192.168.178.32/status.json from the measurement machine, or edit the URL in check_gude_modified.py.
• IndexError / KeyError on sensor_values — the device returned a document that does not have the expected sensor layout.
• The script needs the requests package to be importable in the environment the tool runs in.