fix: OTEL_TRACES_EXPORTER and OTEL_PROPAGATORS

sdk/Gemfile

@@ -11,3 +11,4 @@ gemspec
 # Use the opentelemetry-api gem from source
 gem 'opentelemetry-api', path: '../api'
 gem 'opentelemetry-common', path: '../common'
+gem 'opentelemetry-exporter-jaeger', path: '../exporter/jaeger'

sdk/lib/opentelemetry/sdk/configurator.rb

@@ -143,41 +143,66 @@ def install_instrumentation
       end
 
       def configure_span_processors
-        processors = @span_processors.empty? ? [default_span_processor] : @span_processors
+        processors = @span_processors.empty? ? [wrapped_exporter_from_env].compact : @span_processors
         processors.each { |p| tracer_provider.add_span_processor(p) }
       end
 
-      def default_span_processor
-        Trace::Export::SimpleSpanProcessor.new(
-          Trace::Export::ConsoleSpanExporter.new
-        )
+      def wrapped_exporter_from_env
+        exporter = ENV.fetch('OTEL_TRACES_EXPORTER', 'otlp')
+        case exporter
+        when 'none' then nil
+        when 'otlp' then fetch_exporter(exporter, 'OpenTelemetry::Exporter::OTLP::Exporter')
+        when 'jaeger' then fetch_exporter(exporter, 'OpenTelemetry::Exporter::Jaeger::CollectorExporter')
+        when 'zipkin' then fetch_exporter(exporter, 'OpenTelemetry::Exporter::Zipkin::Exporter')
+        else
+          OpenTelemetry.logger.warn "The #{exporter} exporter is unknown and cannot be configured, spans will not be exported"
+          nil
+        end
       end
 
-      def configure_propagation
-        OpenTelemetry.propagation = create_propagator(@injectors || default_injectors,
-                                                      @extractors || default_extractors)
+      def configure_propagation # rubocop:disable Metrics/AbcSize, Metrics/CyclomaticComplexity
+        propagators = ENV.fetch('OTEL_PROPAGATORS', 'tracecontext,baggage').split(',')
+        injectors, extractors = propagators.uniq.collect do |propagator|
+          case propagator
+          when 'tracecontext'
+            [OpenTelemetry::Trace::Propagation::TraceContext.text_map_injector, OpenTelemetry::Trace::Propagation::TraceContext.text_map_extractor]
+          when 'baggage'
+            [OpenTelemetry::Baggage::Propagation.text_map_injector, OpenTelemetry::Baggage::Propagation.text_map_extractor]
+          when 'b3' then fetch_propagator(propagator, 'OpenTelemetry::Propagator::B3::Single')
+          when 'b3multi' then fetch_propagator(propagator, 'OpenTelemetry::Propagator::B3::Multi', 'b3')
+          when 'jaeger' then fetch_propagator(propagator, 'OpenTelemetry::Propagator::Jaeger')
+          when 'xray' then fetch_propagator(propagator, 'OpenTelemetry::Propagator::XRay')
+          when 'ottrace' then fetch_propagator(propagator, 'OpenTelemetry::Propagator::OTTrace')
+          else
+            OpenTelemetry.logger.warn "The #{propagator} propagator is unknown and cannot be configured"
+            [Context::Propagation::NoopInjector.new, Context::Propagation::NoopExtractor.new]
+          end
+        end.transpose
+        OpenTelemetry.propagation = create_propagator(@injectors || injectors.compact,
+                                                      @extractors || extractors.compact)
       end
 
       def create_propagator(injectors, extractors)
         if injectors.size > 1 || extractors.size > 1
           Context::Propagation::CompositePropagator.new(injectors, extractors)
         else
-          Context::Propagation::Propagator.new(injectors, extractors)
+          Context::Propagation::Propagator.new(injectors.first, extractors.first)
         end
       end
 
-      def default_injectors
-        [
-          OpenTelemetry::Trace::Propagation::TraceContext.text_map_injector,
-          OpenTelemetry::Baggage::Propagation.text_map_injector
-        ]
+      def fetch_propagator(name, class_name, gem_suffix = name)
+        propagator_class = Kernel.const_get(class_name)
+        [propagator_class.text_map_injector, propagator_class.text_map_extractor]
+      rescue NameError
+        OpenTelemetry.logger.warn "The #{name} propagator cannot be configured - please add opentelemetry-propagator-#{gem_suffix} to your Gemfile"
+        [nil, nil]
       end
 
-      def default_extractors
-        [
-          OpenTelemetry::Trace::Propagation::TraceContext.text_map_extractor,
-          OpenTelemetry::Baggage::Propagation.text_map_extractor
-        ]
+      def fetch_exporter(name, class_name)
+        Trace::Export::BatchSpanProcessor.new(Kernel.const_get(class_name).new)
+      rescue NameError
+        OpenTelemetry.logger.warn "The #{name} exporter cannot be configured - please add opentelemetry-exporter-#{name} to your Gemfile, spans will not be exported"
+        nil
       end
     end
   end

sdk/opentelemetry-sdk.gemspec

@@ -31,6 +31,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency 'bundler', '>= 1.17'
   spec.add_development_dependency 'faraday', '~> 0.13'
   spec.add_development_dependency 'minitest', '~> 5.0'
+  spec.add_development_dependency 'opentelemetry-exporter-jaeger', '~> 0.14.0'
   spec.add_development_dependency 'rake', '~> 12.0'
   spec.add_development_dependency 'rubocop', '~> 0.73.0'
   spec.add_development_dependency 'simplecov', '~> 0.17'

sdk/test/opentelemetry/sdk/configurator_test.rb

@@ -5,6 +5,7 @@
 # SPDX-License-Identifier: Apache-2.0
 
 require 'test_helper'
+require 'opentelemetry/exporter/jaeger'
 
 describe OpenTelemetry::SDK::Configurator do
   let(:configurator) { OpenTelemetry::SDK::Configurator.new }
@@ -134,6 +135,27 @@
 
         _(injectors_for(OpenTelemetry.propagation)).must_equal([injector])
       end
+
+      it 'can be set by environment variable' do
+        expected_injectors = [OpenTelemetry::Baggage::Propagation.text_map_injector]
+
+        with_env('OTEL_PROPAGATORS' => 'baggage') do
+          configurator.configure
+        end
+
+        _(injectors_for(OpenTelemetry.propagation)).must_equal(expected_injectors)
+      end
+
+      it 'defaults to none with invalid env var' do
+        with_env('OTEL_PROPAGATORS' => 'unladen_swallow') do
+          configurator.configure
+        end
+
+        _(injectors_for(OpenTelemetry.propagation).length).must_equal(1)
+        _(injectors_for(OpenTelemetry.propagation).first).must_be_instance_of(
+          Context::Propagation::NoopInjector
+        )
+      end
     end
 
     describe '#extractors' do
@@ -155,6 +177,27 @@
 
         _(extractors_for(OpenTelemetry.propagation)).must_equal([extractor])
       end
+
+      it 'can be set by environment variable' do
+        expected_extractors = [OpenTelemetry::Baggage::Propagation.text_map_extractor]
+
+        with_env('OTEL_PROPAGATORS' => 'baggage') do
+          configurator.configure
+        end
+
+        _(extractors_for(OpenTelemetry.propagation)).must_equal(expected_extractors)
+      end
+
+      it 'defaults to none with invalid env var' do
+        with_env('OTEL_PROPAGATORS' => 'unladen_swallow') do
+          configurator.configure
+        end
+
+        _(extractors_for(OpenTelemetry.propagation).length).must_equal(1)
+        _(extractors_for(OpenTelemetry.propagation).first).must_be_instance_of(
+          Context::Propagation::NoopExtractor
+        )
+      end
     end
 
     describe 'tracer_provider' do
@@ -176,11 +219,11 @@
     end
 
     describe 'span processors' do
-      it 'defaults to SimpleSpanProcessor w/ ConsoleSpanExporter' do
+      it 'defaults to NoopSpanProcessor if no valid exporter is available' do
         configurator.configure
 
         _(OpenTelemetry.tracer_provider.active_span_processor).must_be_instance_of(
-          OpenTelemetry::SDK::Trace::Export::SimpleSpanProcessor
+          OpenTelemetry::SDK::Trace::NoopSpanProcessor
         )
       end
 
@@ -197,6 +240,29 @@
           OpenTelemetry::SDK::Trace::Export::BatchSpanProcessor
         )
       end
+
+      it 'can be set by environment variable' do
+        with_env('OTEL_TRACES_EXPORTER' => 'jaeger') do
+          configurator.configure
+        end
+
+        _(OpenTelemetry.tracer_provider.active_span_processor).must_be_instance_of(
+          OpenTelemetry::SDK::Trace::Export::BatchSpanProcessor
+        )
+        _(OpenTelemetry.tracer_provider.active_span_processor.instance_variable_get(:@exporter)).must_be_instance_of(
+          OpenTelemetry::Exporter::Jaeger::CollectorExporter
+        )
+      end
+
+      it 'accepts "none" as an environment variable value' do
+        with_env('OTEL_TRACES_EXPORTER' => 'none') do
+          configurator.configure
+        end
+
+        _(OpenTelemetry.tracer_provider.active_span_processor).must_be_instance_of(
+          OpenTelemetry::SDK::Trace::NoopSpanProcessor
+        )
+      end
     end
 
     describe 'instrumentation installation' do
@@ -238,10 +304,18 @@
   end
 
   def extractors_for(propagator)
-    propagator.instance_variable_get(:@extractors) || propagator.instance_variable_get(:@extractor)
+    if propagator.instance_of? Context::Propagation::CompositePropagator
+      propagator.instance_variable_get(:@extractors)
+    else
+      [propagator.instance_variable_get(:@extractor)]
+    end
   end
 
   def injectors_for(propagator)
-    propagator.instance_variable_get(:@injectors) || propagator.instance_variable_get(:@injector)
+    if propagator.instance_of? Context::Propagation::CompositePropagator
+      propagator.instance_variable_get(:@injectors)
+    else
+      [propagator.instance_variable_get(:@injector)]
+    end
   end
 end