How to only collect/export metrics in OpenTelemetry where counter is larger than zero?

[claria]

i asked the same question around 3 months ago on stackoverflow but never received an answer. I think this is an interesting usecase and i am still looking for a proper way to do it so i try my luck here:

I am exporting some counter metrics (message counts per device) to Azure Monitor (however i think this question must be answered independent from chosen export).

I count messages with different attributes (e.g. name of device which sent the message) and export the metrics periodically. I am using Delta temporality. Since the devices sometimes send messages and sometimes not, the counter is often zero for a attribute set. Currently the metrics are exported always for all attribute sets, even for the ones where the counter is zero.

from opentelemetry import metrics
from opentelemetry.sdk.metrics import Counter, MeterProvider
from opentelemetry.sdk.metrics.export import (
    AggregationTemporality,
    ConsoleMetricExporter,
    PeriodicExportingMetricReader,
)

reader = PeriodicExportingMetricReader(ConsoleMetricExporter(
    preferred_temporality={Counter: AggregationTemporality.DELTA}),
    export_interval_millis=5000)

metrics.set_meter_provider(MeterProvider(metric_readers=[reader]))

meter = metrics.get_meter_provider().get_meter("sample")

counter = meter.create_counter("attr_counter")

attr_set = {
    "device_name": "device1"
}
counter.add(1, attr_set)

time.sleep(3)

attr_set = {
    "device_name": "device2"
}
counter.add(1, attr_set)

which results in the following output

[{"attributes": {"device_name": "device1"}, "start_time_unix_nano": 1669972853579471100, "time_unix_nano": 1669972855585084900, "value": 1}]

[{"attributes": {"device_name": "device1"}, "start_time_unix_nano": 1669972857904481900, "time_unix_nano": 1669972859918395000, "value": 0}, {"attributes": {"device_name": "device2"}, "start_time_unix_nano": 1669972853579471100, "time_unix_nano": 1669972859918395000, "value": 1}]

I want to achieve that the metrics are only exported (or collected) if the counter for an attribute set is larger than zero.

Currently i am using a very ugly way that i subclass the exporter and ignore points where the value is 0, but i would like to know what's the recommended way to achieve this behaviour.

[ocelotl]

Hello

That does not seem like a bad solution at all. There are many custom "configurations" that anyone can need for their exporters and using a subclass is a clean way of achieving that.