Option to disable OpenTelemetry

[hansingt]

I'm currently facing issues with buildkit always enabling the OTEL traces exporter during build.

The software I'm trying to run during the build, uses OTEL itself. Thus, because buildkit configures the OTEL_TRACES_EXPORTER environment variable, it tries to export the traces it generates. But because of grpc/grpc#9538 this fails, as buildkit seems to use SSL for GRPC communication, but does not configure the exporter with TLS (grpc+tls).

Because of this, I tried to disable the traces export, because I do not need it at all. But setting the --driver-opt="env.OTEL_TRACES_EXPORTER=none" did not work, even though the environment variable is set on the build container.

For reference: I'm using a Fedora 40 with the following versions:

> docker --version
Docker version 26.1.3, build b72abbb
> docker buildx version
github.com/docker/buildx v0.14.0 171fcbe
> docker buildx inspect container
Name:          container
Driver:        docker-container
Last Activity: 2024-05-30 13:37:20 +0000 UTC

Nodes:
Name:                  container0
Endpoint:              unix:///var/run/docker.sock
Driver Options:        env.OTEL_TRACES_EXPORTER="none"
Status:                running
BuildKit daemon flags: --allow-insecure-entitlement=network.host
BuildKit version:      v0.13.2
Platforms:             linux/amd64, linux/amd64/v2, linux/amd64/v3, linux/arm64, linux/riscv64, linux/ppc64, linux/ppc64le, linux/s390x, linux/386, linux/mips64le, linux/mips64, linux/arm/v7, linux/arm/v6
Labels:
 org.mobyproject.buildkit.worker.executor:         oci
 org.mobyproject.buildkit.worker.hostname:         4c03dedd3e04
 org.mobyproject.buildkit.worker.network:          host
 org.mobyproject.buildkit.worker.oci.process-mode: sandbox
 org.mobyproject.buildkit.worker.selinux.enabled:  false
 org.mobyproject.buildkit.worker.snapshotter:      overlayfs
GC Policy rule#0:
 All:           false
 Filters:       type==source.local,type==exec.cachemount,type==source.git.checkout
 Keep Duration: 48h0m0s
 Keep Bytes:    488.3MiB
GC Policy rule#1:
 All:           false
 Keep Duration: 1440h0m0s
 Keep Bytes:    174.2GiB
GC Policy rule#2:
 All:        false
 Keep Bytes: 174.2GiB
GC Policy rule#3:
 All:        true
 Keep Bytes: 174.2GiB

I've tried to explicitly downgrade buildkit to v0.12.5 as described in #4743 but it does not solve my issue.

So the question is: How can I disable OpenTelemetry in buildkit and prevent it from adding the ´OTEL_TRACES_EXPORTER` environment variable to the build env?

Thanks in advance!