[Samplers] Allow for more than one span_kind

[dol]

Component(s)

samplers

Is your feature request related to a problem? Please describe.

The declarative configuration RuleBasedRoutingSampler currently only supports defining multiple rules. But this rules only apply for one span_kind.

In a Spring boot application application typically the actuator endpoint will be dropped by the sampler. In addition some background tasks (span_kind=Internal) should also be dropped.
Currently this is not possible at the moment

  sampler:
    parent_based:
      root:
        rule_based_routing:
          fallback_sampler:
            always_on:
          span_kind: SERVER # Should be defined on the rules level
          rules:
            # Drop spans where url.path matches the regex /actuator.* (i.e. spring boot actuator endpoints).
            - action: DROP
              attribute: url.path
              pattern: /actuator.*
            # Drop some async database lookups, span_kind=Internal
            - action: DROP
              attribute: db.sql.table
              pattern: ACT_RU_JOB

Describe the solution you'd like

Introduce a set of rules to allow for more samplers.

  sampler:
    parent_based:
      root:
        rule_based_routing:
          fallback_sampler:
            always_on:
          rule_sets:
            - span_kind: SERVER
              rules:
              # Drop spans where url.path matches the regex /actuator.* (i.e. spring boot actuator endpoints).
              - action: DROP
                attribute: url.path
                pattern: /actuator.*
            - span_kind: Internal
              rules:
              - action: DROP
                attribute: db.sql.table
                pattern: ACT_RU_JOB

Describe alternatives you've considered

It similar to the open-telemetry/opentelemetry-configuration#102 proposal.

Additional context

No response

[AlessandroPinna]

I'm also looking for a similar solution. I need to drop different kinds of root level spans (SERVER, CLIENT, CONSUMER), so it would be great to have the span_kind at the rule level, or at least to be able to match all span kinds with a single rule_based_routing.

[dol]

@AlessandroPinna
The latest release https://github.com/open-telemetry/opentelemetry-java-contrib/releases/tag/v1.51.0 will bring a new CEL-Based sampler which gives you more filter capabilities.

The maven artefact can be found at https://central.sonatype.com/artifact/io.opentelemetry.contrib/opentelemetry-cel-sampler/overview

[AlessandroPinna]

Thanks a lot @dol, that's exactly what I was looking for

[dol]

Closed in favour of the CEL-Based sampler.