1fanwang commented on code in PR #71564:
URL: https://github.com/apache/airflow/pull/71564#discussion_r3798858140
##########
airflow-core/docs/administration-and-deployment/logging-monitoring/metrics.rst:
##########
@@ -98,6 +98,42 @@ Add the Collector details to your configuration file e.g.
``airflow.cfg``
`SDK environment variable documentation
<https://opentelemetry.io/docs/specs/otel/configuration/sdk-environment-variables/#periodic-exporting-metricreader>`_
for more information.
+Replicated components
+---------------------
+
+Every Airflow process reports the same ``service.name``, so a deployment
running more than one
+replica of a component — schedulers in high availability, several triggerers
or Dag processors —
+sends telemetry the backend cannot attribute to an individual process.
+
+Gauges are where this shows up in the data. Each scheduler samples the
metadata database on its
+own loop and exports a value for the same series, so ``pool.open_slots`` and
its siblings keep
+whichever export arrived last and appear to flap between replicas' samples.
+
+Give each replica a unique ``service.instance.id`` so its samples form their
own series:
+
+.. code-block:: bash
+
+ # on each scheduler, triggerer or Dag processor
+ export OTEL_RESOURCE_ATTRIBUTES="service.instance.id=$(hostname)"
+
+Airflow merges ``OTEL_RESOURCE_ATTRIBUTES`` into the OpenTelemetry resource,
so nothing else needs
+configuring. Replicas can then be aggregated at query time instead of
overwriting one another —
+for example, the lowest number of open slots any scheduler observed:
+
+.. code-block:: text
+
+ min by (pool_name) (airflow_pool_open_slots)
+
+Backends implementing the OpenTelemetry `Prometheus compatibility
+<https://opentelemetry.io/docs/specs/otel/compatibility/prometheus_and_openmetrics/>`_
spec expose
+``service.instance.id`` as the ``instance`` label.
Review Comment:
Reframed in
https://github.com/apache/airflow/commit/f6214bbc380e01ccdb4923971090715c80215aaa.
It now leads with the fact that how the attributes surface depends on the
backend, and cites the OpenTelemetry Prometheus-compatibility spec rather than
any specific backend
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