Grafana: Only permit numeric fields to be established on Graph panels

[amotl]

Hi again,

when testing GH-125 in production, we discovered at ¹ that Grafana would croak on non-numeric fields being established on the Graph panel. They will make the panel croak like InfluxDB Error: unsupported mean iterator type: *query.stringInterruptIterator or InfluxDB Error: not executed ².

While the ecowitt2mqtt decoder strips all text fields like PASSKEY, stationtype, and model from the original data, it adds a few other text fields through its computed data:

{
  "batt1": "OFF",
  "wh65batt": "OFF",
  "wh25batt": "OFF",
  "frostrisk": "No risk",
  "humidex_perception": "Comfortable",
  "thermalperception": "Dry"
}

This patch fixes it, by skipping all non-numeric fields when provisioning the Grafana panel.

With kind regards,
Andreas.

Footnotes

1. https://climart.hiveeyes.org/grafana/d/climart-testdrive/climart-testdrive ↩

2. Did anyone of you observe this flaw in the past already, @Tonkenfo, @wetterfrosch, or @ClemensGruber? ↩

[amotl]

A corresponding test case for this issue is part of GH-125.

kotori/test/test_device_fineoffset.py

Lines 128 to 132 in 1391232

	# Verify that text fields are not part of the graph. Otherwise, Grafana would croak like:
	# - InfluxDB Error: unsupported mean iterator type: *query.stringInterruptIterator
	# - InfluxDB Error: not executed
	assert "batt1" not in fieldnames, "'batt1' should have been removed, because it is a text field"
	assert "frostrisk" not in fieldnames, "'frostrisk' should have been removed, because it is a text field"