Honor OTEL_PROPAGATORS when propagating trace context across Airflow

[rjgoyln]

Summary

Airflow instantiated TraceContextTextMapPropagator() directly at every trace-context boundary instead of using the globally configured propagators. As a result, OTEL_PROPAGATORS had no effect inside Airflow: vendor propagators were ignored, Baggage was dropped across component boundaries, and worker-to-API-server propagation could fail when tracecontext was not configured.

This replaces the hardcoded propagators with opentelemetry.propagate, matching the Execution API middleware and allowing Airflow to honor the configured propagation strategy consistently.

Changes

• Replaced all hardcoded TraceContextTextMapPropagator() usages with propagate.inject and propagate.extract.
• Stopped filtering run-conf carriers to only traceparent and tracestate, allowing configured propagators to read and write their own fields.
• Kept the bare-string airflow/dagrun_parent_trace_context shorthand pinned to the W3C propagator. The shorthand's value is defined as a W3C trace-context string, while the mapping form remains propagator-agnostic.
• Added documentation for OTEL_PROPAGATORS and trace-context propagation.
• Updated tests to verify baggage round-tripping and backward compatibility.
• Added newsfragment: airflow-core/newsfragments/70840.improvement.rst.

Compatibility

No behavior changes are expected with the default OTEL_PROPAGATORS=tracecontext,baggage: carriers remain byte-identical unless baggage is present.

Existing W3C carriers continue to extract correctly, and the documented bare-string airflow/dagrun_parent_trace_context shorthand remains supported regardless of the configured propagators.

Scope

Addresses Issue 2 of #70388 only. Issues 1 and 3 remain separate.

• Related: Support OpenTelemetry Auto-Instrumentation, Distros & Configurators #70388

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Was generative AI tooling used to co-author this PR?

• Yes (please specify the tool below)
  Generated-by: Claude Code (Opus 5)

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Important

🛠️ Maintainer triage note for @rjgoyln · by @potiuk · 2026-08-13 12:55 UTC

Helpful heads-up from the maintainers — please address before this PR can be reviewed:

• ❌ Merge conflicts. See docs.

Full list of what we check: Pull Request quality criteria.

The ball is in your court — you've been assigned to this PR. Fix the above, then mark it Ready for review.

_{Automated triage — may be imperfect; a maintainer takes the next look.}

[potiuk]

Hello @rjgoyln - thank you for your contributions to Apache Airflow!

The Airflow community has introduced a limit of 5 open pull requests at a time for contributors without write access to the repository. You currently have 24 open pull requests, so - as a one-time step of introducing the limit - we closed the ones where maintainers have not engaged yet:

• Support OpenTelemetry auto-instrumentation and vendor distros #70758 - Support OpenTelemetry auto-instrumentation and vendor distros
• Honor OTEL_PROPAGATORS when propagating trace context across Airflow #70840 - Honor OTEL_PROPAGATORS when propagating trace context across Airflow
• Fix API client errors losing detail behind a reverse proxy #70936 - Fix API client errors losing detail behind a reverse proxy
• Fix airflowctl config lint filters matching partial config names #70940 - Fix airflowctl config lint filters matching partial config names
• Stop failing reschedule-mode sensors on a stale executor success #71194 - Stop failing reschedule-mode sensors on a stale executor success
• Drop the cncf.kubernetes provider dependency from airflow-core tests #71868 - Drop the cncf.kubernetes provider dependency from airflow-core tests
• Drop the git provider dependency from airflow-core tests #72041 - Drop the git provider dependency from airflow-core tests
• Fail deferred sensors on non-timeout errors when soft_fail is set #72053 - Fail deferred sensors on non-timeout errors when soft_fail is set
• Drop the celery provider dependency from airflow-core tests #72249 - Drop the celery provider dependency from airflow-core tests
• Honor config_file in deferrable Kubernetes tasks #72301 - Honor config_file in deferrable Kubernetes tasks
• Fix Dataproc job not cancelled when killing a deferred task #72591 - Fix Dataproc job not cancelled when killing a deferred task
• Stop the scheduler deadlocking with the triggerer on deferred-task timeouts #72595 - Stop the scheduler deadlocking with the triggerer on deferred-task timeouts
• Make the scheduler's HITL and orphan sweeps retry transient DB errors #72596 - Make the scheduler's HITL and orphan sweeps retry transient DB errors
• Keep the triggerer running when a trigger constructor raises #72758 - Keep the triggerer running when a trigger constructor raises
• Stop failing scheduled tasks when a serialized Dag is briefly missing #72814 - Stop failing scheduled tasks when a serialized Dag is briefly missing
• Stop fetching the run conf once per task instance in the scheduler #73022 - Stop fetching the run conf once per task instance in the scheduler
• Catch format-string arguments passed to exception constructors #73076 - Catch format-string arguments passed to exception constructors
• Fail deferrable KPO when a GC'd pod takes its XCom with it #73131 - Fail deferrable KPO when a GC'd pod takes its XCom with it
• Block new EM102 f-string exception messages in prek #73166 - Block new EM102 f-string exception messages in prek
• Fail the local yml mounts prek hook when synchronization fails #73170 - Fail the local yml mounts prek hook when synchronization fails
• Fix provider.yaml doc URL check with several suspended providers #73204 - Fix provider.yaml doc URL check with several suspended providers

These pull requests stay open because maintainers are already engaged in them - they count towards your limit:

• Batch upstream map-length lookups when resolving mapped kwargs #70620 - Batch upstream map-length lookups when resolving mapped kwargs
• Re-anchor custom queued deadline references when a Dag run is cleared #71850 - Re-anchor custom queued deadline references when a Dag run is cleared
• Make the default task failure email say what failed #73221 - Make the default task failure email say what failed

This is not a judgement of you or of your changes. We never told contributors before that opening many pull requests at once was a problem, so there is nothing to feel bad about - and nothing is lost: your branches, commits and the review history stay where they are.

What we ask you to do is to make your first prioritization decision: choose which of the pull requests above matter most to you, and reopen them (up to 5 open at a time, including the ones still open) with the "Reopen pull request" button or gh pr reopen <PR_NUMBER> --repo apache/airflow. Reopen the ones you are ready to follow through - keep them rebased, respond to review comments and fix failing checks.

While your pull requests are waiting for review, the most valuable thing you can do is help in other ways - reviewing other contributors' pull requests, helping with issues, and taking part in the discussions on the devlist and Slack.

Why we introduced the limit, what it means for you and how to reopen or restore a pull request is explained in https://github.com/apache/airflow/blob/main/contributing-docs/32_open_pull_request_limit.rst.

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Drafted-by: Claude Code (Opus 5); reviewed by @potiuk before posting