"unsupported opentelemetry exporter None" with "docker-compose up" about compose

[ndeloof]

Documentation is highly confusing regarding .env file, a rewrite is on its way (docker/docs#19541)
.env in your working directory is used to interpolate variables in your compose.yaml file, as described here but it is also used to configure Compose itself. This can be used to set COMPOSE_* variables and typically change OTEL_METRICS_EXPORTER. So the conflict here

The requirement for the containerized app is to have the value as "None" verbatim (not lowercase).

That's a bit weird as this is an non-standard value, but I assume you have no impact on this :) I guess your compose.yaml file has env_file: .env set for container, one option is for you to use a distinct file name and a dedicated xx.env file for this container, or you can also override value in compose.yaml with environment: OTEL_METRICS_EXPORTER: None (environment has precedence on env_file)

[ndeloof]

Please check you have OTEL_TRACES_EXPORTER variable set. none value is supported but should be lowercase

[greatvovan]

export OTEL_TRACES_EXPORTER=none did not help, but OTEL_METRICS_EXPORTER=none did.

I wonder, though, since when it is a requirement to have these variables set with docker-compose? Is is documented somewhere? Why is unset variable not interpreted as none by default?

[ndeloof]

This is not the default value, this None (uppercase) is probably set in your environment.

[ndeloof]

Can you please try running docker buildx build . to build your Dockerfile and confirm you get a distinct behavior ?

[greatvovan]

Yes, your command succeeds in the same shell where docker-compose fails.

[ndeloof]

I can't tell what's wrong here. OTEL_METRICS_EXPORTER is the standard variable used to configure opentelemetry (https://opentelemetry.io/docs/languages/sdk-configuration/general/#otel_metrics_exporter) and value is set by end user's environment, not compose. Have you checked you don't have value set in your .env file ?

[greatvovan]

Okay, I found that I do have .env file and it has OTEL_METRICS_EXPORTER=None, which is needed for the containerized app. The requirement for the containerized app is to have the value as "None" verbatim (not lowercase). What I don't understand is why it affects the docker-compose utility itself, since as described in the documentation

An .env file in Docker Compose is a text file used to define environment variables that should be made available to Docker containers when running docker compose up. ... The .env file is the default method for setting environment variables in your containers.

I read it as the .env file is treated as a collection of environment variables that get propagated to the containers. In my user environment I have no OTEL_METRICS_EXPORTER variable set:

% echo .$OTEL_METRICS_EXPORTER.
..

Is it documented somewhere that the utility treats the .env file as its own environment?

[greatvovan]

Thank you for linking the docs, though I find that mixing of container and compose environment confusing...

That's a bit weird as this is an non-standard value

After looking into the implementation, none will be accepted by the containerized software as well, but it is still good to change the setup to avoid this overlap.