feat(active_job): add active_job_propagate_traces config option

Mirrors Sidekiq's propagate_traces flag. When set to false, trace
propagation headers are not injected into the serialized job payload
and the consumer starts a new unconnected transaction.

Defaults to true (existing behaviour is preserved).

Co-Authored-By: github-copilot <noreply@example.com>

Author: solnic

sentry-rails/lib/sentry/rails/active_job.rb

@@ -27,8 +27,10 @@ def serialize
 
         begin
           sentry_data = {}
-          headers = Sentry.get_trace_propagation_headers
-          sentry_data["trace_propagation_headers"] = headers if headers && !headers.empty?
+          if Sentry.configuration.rails.active_job_propagate_traces
+            headers = Sentry.get_trace_propagation_headers
+            sentry_data["trace_propagation_headers"] = headers if headers && !headers.empty?
+          end
 
           if Sentry.configuration.send_default_pii
             user = Sentry.get_current_scope.user || {}

sentry-rails/lib/sentry/rails/configuration.rb

@@ -172,6 +172,11 @@ class Configuration
       # Set this option to true if you want Sentry to capture each retry failure
       attr_accessor :active_job_report_on_retry_error
 
+      # Whether we should inject trace propagation headers into the serialized job
+      # payload in order to have a connected trace between producer and consumer.
+      # Defaults to true. Set to false to opt out.
+      attr_accessor :active_job_propagate_traces
+
       # Configuration for structured logging feature
       # @return [StructuredLoggingConfiguration]
       attr_reader :structured_logging
@@ -193,6 +198,7 @@ def initialize
         @db_query_source_threshold_ms = 100
         @active_support_logger_subscription_items = Sentry::Rails::ACTIVE_SUPPORT_LOGGER_SUBSCRIPTION_ITEMS_DEFAULT.dup
         @active_job_report_on_retry_error = false
+        @active_job_propagate_traces = true
         @structured_logging = StructuredLoggingConfiguration.new
       end
     end

sentry-rails/spec/active_job/shared_examples/tracing/trace_propagation.rb

@@ -47,4 +47,37 @@ def perform; end
     expect(consumer_transaction).not_to be_nil
     expect(consumer_transaction.contexts.dig(:trace, :trace_id)).to eq(parent_trace_id)
   end
+
+  context "when active_job_propagate_traces is false" do
+    let(:configure_sentry) do
+      proc do |config|
+        config.traces_sample_rate = 1.0
+        config.rails.active_job_propagate_traces = false
+      end
+    end
+
+    it "does not inject trace headers into the job payload" do
+      within_parent_transaction do
+        successful_job.perform_later
+      end
+
+      payload = queue_adapter.enqueued_jobs.last
+      sentry_payload = (payload[:_sentry_full_payload] || payload)["_sentry"]
+      expect(sentry_payload&.dig("trace_propagation_headers")).to be_nil
+    end
+
+    it "starts a new unconnected consumer transaction" do
+      parent_trace_id = nil
+
+      within_parent_transaction do |parent|
+        parent_trace_id = parent.trace_id
+        successful_job.perform_later
+      end
+
+      drain
+
+      expect(consumer_transaction).not_to be_nil
+      expect(consumer_transaction.contexts.dig(:trace, :trace_id)).not_to eq(parent_trace_id)
+    end
+  end
 end