New class to push manually metrics : CustomMetricReader

[samkerr4coding]

Hello,

For my own purpose i did develop a class in opentelemetry.sdk.metrics._internal.export called CustomMetricReader.
It does corresponds to the MetricReader interface signature and allows a manual control over the operation of sending metrics in prometheus (manual trigger for metrics to be pushed into the remote write endpoint of prometheus).

The classe is called CustomMetricReader and i use it this way :

import random

from opentelemetry import metrics
from opentelemetry.exporter.prometheus_remote_write import PrometheusRemoteWriteMetricsExporter
from opentelemetry.sdk.metrics import MeterProvider
from opentelemetry.sdk.metrics._internal.export import CustomMetricReader
from opentelemetry.sdk.resources import Resource, SERVICE_NAME

resource = Resource(attributes={
    SERVICE_NAME: "service name"
})

exporter = PrometheusRemoteWriteMetricsExporter(
    endpoint="http://localhost:9090/api/v1/write",
    timeout=30
)
reader = CustomMetricReader(exporter, 100)
provider = MeterProvider(resource=resource, metric_readers=[reader])
metrics.set_meter_provider(provider)

meter = metrics.get_meter(__name__)
request_latency = meter.create_histogram("my_histogram")
request_min_max = meter.create_counter("my_counter")

i = 0
num = random.randint(0, 1000)
testing_labels = {"environment": "testing"}
while i < 100:
    request_latency.record(random.uniform(0, 100), {"service_nam": "testing"})
    request_min_max.add(num % 181 + 200, testing_labels)
    i = i + 1
reader.collect()

Can you tell me if this feature is relevant? if yes can you help me on contributing this is the first time i contribute on opentelemtry.

Here is my fork :

https://github.com/samkerr4coding/opentelemetry-python/tree/custom_metric_reader

Many thanks
Samir KERROUMI

[lzchen]

We have this change to address this use case. Set export interval to math.inf should do the trick.

[samkerr4coding]

Hello @lzchen thanks for this information!!! i may be wrong but maybe this feature is not obvious enough no? i did look into the doc how to push "on demand" and i didnt find it until you pointed this.

[lzchen]

Yeah that's a great point. We have purposefully made this as a hidden functionality because we were not sure whether or not a feature like this was in demand enough to warrant documenting (since math.inf intuitively doesn't make sense and may confuse people) or have a full blown new class for. But we still wanted to make it available for the select few users that did want to have this functionality.

[samkerr4coding]

Thanks for you reply @lzchen i tested the PeriodicMetricReader with the Math.inf param and it fullfill my use case.

Precisely my use case was relative to a Performance "smoke test" done in python in which we are making few calls and collect few metrics. As i'm producing few metric i wanted at the time to see if a manual explicit exporter was available (because i want to use the remote write feat in prometheus as well).

Let me know if you want to move ahead with a CustomMetricReader for explicit manual push i let me Pull request opened and i would be glad to contribute.

Many thanks