feat: Allow disabling of redis root spans (#777)

Author: robertlaurin

instrumentation/redis/CHANGELOG.md

@@ -1,5 +1,9 @@
 # Release History: opentelemetry-instrumentation-redis
 
+### Unreleased
+
+* ADDED: Configuration option to enable or disable redis root spans [#777](https://github.com/open-telemetry/opentelemetry-ruby/pull/777)
+
 ### v0.18.0 / 2021-05-21
 
 * ADDED: Updated API depedency for 1.0.0.rc1

instrumentation/redis/lib/opentelemetry/instrumentation/redis/instrumentation.rb

@@ -19,8 +19,9 @@ class Instrumentation < OpenTelemetry::Instrumentation::Base
           defined?(::Redis)
         end
 
-        option :peer_service, default: nil, validate: :string
-        option :enable_statement_obfuscation, default: true, validate: :boolean
+        option :peer_service,                 default: nil,   validate: :string
+        option :trace_root_spans,             default: true,  validate: :boolean
+        option :enable_statement_obfuscation, default: true,  validate: :boolean
 
         private
 

instrumentation/redis/lib/opentelemetry/instrumentation/redis/patches/client.rb

@@ -13,7 +13,9 @@ module Client
           MAX_STATEMENT_LENGTH = 500
           private_constant :MAX_STATEMENT_LENGTH
 
-          def process(commands) # rubocop:disable Metrics/AbcSize, Metrics/MethodLength
+          def process(commands) # rubocop:disable Metrics/AbcSize, Metrics/MethodLength, Metrics/PerceivedComplexity, Metrics/CyclomaticComplexity
+            return super unless config[:trace_root_spans] || OpenTelemetry::Trace.current_span.context.valid?
+
             host = options[:host]
             port = options[:port]
 

instrumentation/redis/test/opentelemetry/instrumentation/redis/patches/client_test.rb

@@ -260,6 +260,31 @@ def redis_with_auth(redis_options = {})
       _(last_span.attributes['db.statement']).must_equal 'SET K x'
     end
 
+    describe 'when trace_root_spans is disabled' do
+      before do
+        instrumentation.instance_variable_set(:@installed, false)
+        instrumentation.install(trace_root_spans: false)
+      end
+
+      it 'traces redis spans with a parent' do
+        redis = redis_with_auth
+        OpenTelemetry.tracer_provider.tracer('tester').in_span('a root!') do
+          redis.set('a', 'b')
+        end
+
+        redis_span = exporter.finished_spans.find { |s| s.name == 'SET' }
+        _(redis_span.name).must_equal 'SET'
+        _(redis_span.attributes['db.statement']).must_equal 'SET ? ?'
+      end
+
+      it 'does not trace redis spans without a parent' do
+        redis = redis_with_auth
+        redis.set('a', 'b')
+
+        _(exporter.finished_spans.size).must_equal 0
+      end
+    end
+
     describe 'when enable_statement_obfuscation is enabled' do
       before do
         instrumentation.instance_variable_set(:@installed, false)