oci: don't override build-provided OpenTelemetry env vars - #6958
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BuildKit injects OTEL_TRACES_EXPORTER (and the OTLP endpoint/protocol) into the build environment whenever a tracing socket is configured, and it did so unconditionally -- appending its values after any the build already set. That made it impossible to opt out or override them; for example `--opt env.OTEL_TRACES_EXPORTER=none` had no effect because BuildKit re-added OTEL_TRACES_EXPORTER=otlp afterwards. Only inject the trace-exporter variables the build has not already set, so a build can override them or opt out of tracing. Fixes moby#4972 Signed-off-by: Kunalbehbud <b.kunal2002@gmail.com>
tonistiigi
approved these changes
Jul 17, 2026
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Fixes #4972
Problem
When a tracing socket is configured, BuildKit injects the OpenTelemetry trace-exporter variables (
OTEL_TRACES_EXPORTER=otlp,OTEL_EXPORTER_OTLP_TRACES_ENDPOINT,OTEL_EXPORTER_OTLP_TRACES_PROTOCOL) into every build environment. It did this unconditionally, appending its own values after any the build already provided. Because a later duplicate wins, there was no way to opt out or override them — as the issue reporter found,--opt env.OTEL_TRACES_EXPORTER=nonehad no effect since BuildKit re-addedOTEL_TRACES_EXPORTER=otlpafterwards. This breaks builds that run OpenTelemetry-instrumented tooling of their own.Change
In
GenerateSpec, only inject the trace-exporter variables the build has not already set. A build can now disable or override tracing per build, e.g.:Behavior is unchanged when the build sets none of these variables (all three are still injected as before).
Tests
Added offline unit tests for the new helper (
executor/oci/spec_test.go): all vars injected when none are set, a user-providedOTEL_TRACES_EXPORTER=noneis preserved (and BuildKit's=otlpis not added), and no user-provided tracing var is overridden.Note
This makes the existing per-build
env.*mechanism work as expected, which I think is the least surprising fix. If you'd instead prefer a daemon-level opt-out (abuildkitd.tomloption), I'm happy to add that as well or instead — just let me know.