If job is of type ActiveJob pull underlying job name from the wrapper

lib/ddtrace/contrib/delayed_job/plugin.rb

@@ -9,7 +9,15 @@ class Plugin < Delayed::Plugin
         def self.instrument(job, &block)
           return block.call(job) unless tracer && tracer.enabled
 
-          tracer.trace(Ext::SPAN_JOB, service: configuration[:service_name], resource: job.name) do |span|
+          # When DelayedJob is used through ActiveJob, we need to parse the payload differentely
+          # to get the actual job name
+          job_name = if job.payload_object.respond_to?(:job_data)
+                       job.payload_object.job_data['job_class']
+                     else
+                       job.name
+                     end
+
+          tracer.trace(Ext::SPAN_JOB, service: configuration[:service_name], resource: job_name) do |span|
             span.set_tag(Ext::TAG_ID, job.id)
             span.set_tag(Ext::TAG_QUEUE, job.queue) if job.queue
             span.set_tag(Ext::TAG_PRIORITY, job.priority)

spec/ddtrace/contrib/delayed_job/plugin_spec.rb

@@ -7,13 +7,26 @@
 require_relative 'delayed_job_active_record'
 
 RSpec.describe Datadog::Contrib::DelayedJob::Plugin, :delayed_job_active_record do
-  let(:sample_job_object) { double('sample_job', perform: nil) }
-  let(:sample_job_class) { class_double('SampleJob', new: sample_job_object) }
+  let(:sample_job_object) do
+    stub_const('SampleJob', Class.new do
+      def perform; end
+    end)
+  end
+  let(:active_job_sample_job_object) do
+    stub_const('ActiveJobSampleJob', Class.new do
+      def perform; end
+
+      def job_data
+        {
+          'job_class' => 'UnderlyingJobClass'
+        }
+      end
+    end)
+  end
+
   let(:tracer) { ::Datadog::Tracer.new(writer: FauxWriter.new) }
 
   before do
-    sample_job_class.as_stubbed_const
-
     Datadog.configure { |c| c.use :delayed_job, tracer: tracer }
 
     Delayed::Worker.delay_jobs = false
@@ -40,12 +53,23 @@
 
   describe 'instrumented job invocation' do
     let(:job_params) { {} }
-    subject(:job_run) { Delayed::Job.enqueue(SampleJob.new, job_params) }
+    subject(:job_run) { Delayed::Job.enqueue(sample_job_object.new, job_params) }
 
     it 'creates a span' do
       expect { job_run }.to change { tracer.writer.spans.first }.to be_instance_of(Datadog::Span)
     end
 
+    context 'when the job looks like Active Job' do
+      subject(:job_run) { Delayed::Job.enqueue(active_job_sample_job_object.new, job_params) }
+      subject(:span) { tracer.writer.spans.first }
+
+      before { job_run }
+
+      it 'has resource name equal to underlying ActiveJob class name' do
+        expect(span.resource).to eq('UnderlyingJobClass')
+      end
+    end
+
     describe 'created span' do
       subject(:span) { tracer.writer.spans.first }
 
@@ -57,7 +81,7 @@
       end
 
       it 'has resource name equal to job name' do
-        expect(span.resource).to eq(RSpec::Mocks::Double.name)
+        expect(span.resource).to eq('SampleJob')
       end
 
       it "span tags doesn't include queue name" do