Unable to add tags to spans

[genebean]

As best as I can tell from reading through things, there doesn't seem to be a way for me to add tags yet. My specific use case here is adding tags to an app instrumented via the opentelemetry-ruby/instrumentation/sinatra/.

[mwear]

👋 @genebean. In OpenTelemetry tags are referred to as attributes. There is a Span#add_attribute method for adding them. If you are trying to get at a Span that has been created by auto-instrumentation, it might be available by calling Tracer#current_span, although that will depend on what other work is being traced at the time.

Let us know if you still have questions.

[genebean]

When configuring ddtrace I can do this:

Datadog.configure do |c|
  c.tracer tags: {
    'service_name' => 'my-application-name',
    'service.version' => version,
  }
end

This gem currently limits me to doing this:

OpenTelemetry::SDK.configure do |c|
  c.add_span_processor(
    OpenTelemetry::SDK::Trace::Export::SimpleSpanProcessor.new(
      OpenTelemetry::Exporters::Jaeger::Exporter.new(
        service_name: 'my-application-name', host: jaeger_host, port: 6831
      )
    )
  )
end

The key difference here is that the only tag / attribute I can set at startup is service_name where as with ddtrace I can set any number of arbitrary tags. The specific issue this is causing for me is that I cannot add service.version from within the application.

[fbogsany]

The correct place to do this is with a Resource, like:

OpenTelemetry::SDK.configure do |c|
  c.resource = OpenTelemetry::SDK::Resources::Resource.create({
    'service_name' => 'my-application-name',
    'service.version' => version,
  })
end

Unfortunately, we haven't yet implemented the mapping from OTel's Resource to Jaeger's Process yet:

opentelemetry-ruby/exporters/jaeger/lib/opentelemetry/exporters/jaeger/exporter.rb

Lines 125 to 133 in 7a10db9

	def encoded_process
	@encoded_process ||= begin
	tags = [] # TODO: figure this out.
	# tags = OpenTelemetry.tracer.resource.label_enumerator.map do |key, value|
	# Thrift::Tag.new('key' => key, 'vType' => Thrift::TagType::STRING, 'vStr' => value)
	# end
	Thrift::Process.new('serviceName' => @service_name, 'tags' => tags)
	end
	end

#314 discusses how we might do this. We don't have consensus yet.