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Last updated: August 7, 2026

Resource Detection

Built-in resource detectors for distribution metadata, Kubernetes pod UID, and automatic service name derivation.

Note: This page is auto-generated from the opentelemetry-ruby-distribution repository.

The distribution builds the OpenTelemetry resource from several detectors applied in order. Later detectors take precedence on attribute key conflicts, except for the distribution identity attributes, which are always applied last.

Upstream detectors

The SDK adds process and SDK attributes automatically. The upstream container detector (opentelemetry-resource-detector-container) adds container.id by reading the container's cgroup file.

Dash0 detectors

Distribution identity

The Distribution detector always adds:

AttributeValue
telemetry.distro.namedash0-ruby
telemetry.distro.versionThe installed gem version

Kubernetes pod UID

The KubernetesPod detector adds k8s.pod.uid when the process is running inside a Kubernetes pod.

It first checks /etc/hosts for the # Kubernetes-managed hosts file marker to confirm a pod context. If the marker is present, it reads the pod UID from cgroup files:

  • cgroup v1: parses /proc/self/mountinfo for a mount path containing /pods/<uid>.
  • cgroup v2: parses /proc/self/cgroup for the penultimate segment of each cgroup line, which encodes the pod UID in slice notation (e.g. kubepods-pod<uid>.slice, with underscores normalized to dashes).

If neither file yields a UID, the detector adds no attribute and fails silently.

Service name fallback

The ServiceNameFallback detector provides a service.name when none has been configured. It checks, in order:

  1. The top-level module <Name> declaration in config/application.rb or config/app.rb (Rails, Hanami).
  2. An inline application class or a run <AppClass> target in config.ru (modular Sinatra, Roda, plain Rack, single-file Rails).
  3. The entry script name ($PROGRAM_NAME), when it is not a known wrapper.

Known wrappers (bundle, puma, rackup, rails, sidekiq, and others) are deliberately skipped rather than used as a service name. When none of these sources yields a useful name, the detector adds no attribute and the SDK's unknown_service default stands.

The fallback is skipped entirely when OTEL_SERVICE_NAME is set, when service.name appears in OTEL_RESOURCE_ATTRIBUTES, or when DASH0_AUTOMATIC_SERVICE_NAME=false.