OpenTelemetry Collector

how OpenTelemetry Collector holds the metrics

Answer : OpenTelemetry Collector only holds the latest metrics. If prometheus scrapes it, the latest value is exported to prometheus

My question is whether Prometheus will get the all metrics between the current time and the previous time of metrics or not?

The experimental condition is as follows.

OtelCollecotr

receivers:
  hostmetrics:
    collection_interval: 2s
    scrapers:
      cpu:
      load:
      memory:
      disk:

Prometheus

global:
  scrape_interval: 15s
  evaluation_interval: 15s

Then, the result is as follows.



Thus, the latest value is hold in otel-collector, but the rest of the metrics between the scrapes will be discarded.
This implicates that the interval for otel-collector to collect the metrics should be same as prometheus's scrape interval unless there are special processors are set.

hostmetrics

opentelemetry-collector-contrib/receiver/hostmetricsreceiver at main · open-telemetry/opentelemetry-collector-contrib

Contrib repository for the OpenTelemetry Collector - open-telemetry/opentelemetry-collector-contrib

github.com

hostmetrics is indicating the container when the opentelemetry-collector is started up as container.

It is possible to catch the host metrics by the steps in the documentation.

(It seems impossible when windows. In windows, the hostmetrics will by default indicate the metrics of the total of docker usage)

Left Window : WSL with top command

Right Window : hostmetrics’s memory usage from otel-collector

Bottom Window: docker stats

The memory usage of hostmetrics is matched with the WSL’s memory usage