[🐛 BUG]: hardcoded sampler-specific configuration for otel plugin

[bazilmarkov]

No duplicates 🥲.

• I have searched for a similar issue in our bug tracker and didn't find any solutions.

What happened?

It appears that the OTEL_TRACES_SAMPLER and OTEL_TRACES_SAMPLER_ARG settings are not having any effect, and the Roadrunner otel plugin is still using the default always_on sampling method.

I have been attempting to use traceidratio with a default sampling rate of 1%, but have not been successful so far.

I have tried to configure it using the global environment variables mentioned on the relevant page, but it seems that the sampler is hardcoded to always be on, as per the code

Version (rr --version)

2024.1.1

How to reproduce the issue?

1. Set up basic otel configuration paired with grpc plugin.

otel:
  resource:
    service_name: ${SERVICE}
    service_version: ${VERSION}
  insecure: true
  exporter: otlp
  endpoint: ${AGENT_HOST}:4318

2. Set up the tracer and sampling rate different from the default always_on using env variables

    OTEL_TRACES_SAMPLER: 'traceidratio'
    OTEL_TRACES_SAMPLER_ARG: '0.01'

3. Make 100 requests to the service.

Expected result: 1% of the spans sent
Current result: 100% of the spans sent

Relevant log output

No response

[rustatian]

Fixed, release planned on this Thursday, May 16.