Update process.pid resource attribute for forked processes (eg. Passenger)

[ykitamura-mdsol]

Hi, I'm trying to figure out how to update the process.pid resource attribute for forked processes:

opentelemetry-ruby/sdk/lib/opentelemetry/sdk/resources/resource.rb

Line 58 in ad7c3b9

SemanticConventions::Resource::PROCESS_PID => Process.pid,

and it seems I need to update @resource of tracer provider in all instrumentations.

so I end up patching this method to OpenTelemetry::Instrumentation::Registry but this method is touching instance variables, it doesn't look so nice:

  def refresh_resource(resource)
    @lock.synchronize do
      @instrumentation.map(&:instance).each do |instrumentation|
        instrumentation.tracer.instance_variable_get(:@tracer_provider)&.instance_variable_set(:@resource, resource)
      end
    end
  end

Please advise me if there is a way to update the process.pid resource attribute properly.

Thank you

[ahayworth]

TracerProvider#initialize accepts a resource argument, so in theory one could first create a new TracerProvider with the desired resource attributes. Then, any tracer you obtain from this custom TracerProvider will have the desired resource attributes as well.

It is not straightforward, though - I wonder if maybe this should be updated whenever the SDK detects a fork... maybe @open-telemetry/ruby-approvers and @open-telemetry/ruby-maintainers have ideas?

[arielvalentin]

I do not have a simple answer for this. What do other Language SDKs do?

Resources are immutable once the SDK is initialized we are unable to change them. When the process is forked it takes the initialized Resource SDK with it. The only way to change it would be to reset the Resource SDK but we probably do not want to reinitialize the entire SDK to update the process.pid resource attribute, especially if it is using custom resources detectors that make API calls (Azure, GCP, etc...).