Fix Sidekiq tracing headers not being overwritten in case of schedules and retries [#2118](#2118) (#2118)

#1774 added
`SentryContextClientMiddleware` to the server middleware chain too.

Sidekiq's scheduler pushes to the client on the server again for
schedules and retries which causes our trace propagation to be broken
for this case.
https://github.com/sidekiq/sidekiq/blob/aadc77a172f1490fb141c7936d2801ca3af925ef/lib/sidekiq/scheduled.rb#L39

Prioritize taking the trace propagation headers from the job whenever
they exist.

Author: sl0thentr0py

Diff for: CHANGELOG.md

@@ -13,6 +13,7 @@
 - Always send envelope trace header from dynamic sampling context [#2113](https://github.com/getsentry/sentry-ruby/pull/2113)
 - Improve `TestHelper`'s setup/teardown helpers ([#2116](https://github.com/getsentry/sentry-ruby/pull/2116))
   - Fixes [#2103](https://github.com/getsentry/sentry-ruby/issues/2103)
+- Fix Sidekiq tracing headers not being overwritten in case of schedules and retries [#2118](https://github.com/getsentry/sentry-ruby/pull/2118)
 
 ## 5.11.0
 

Diff for: sentry-sidekiq/lib/sentry/sidekiq/sentry_context_middleware.rb

@@ -59,7 +59,7 @@ def call(_worker_class, job, _queue, _redis_pool)
 
         user = Sentry.get_current_scope.user
         job["sentry_user"] = user unless user.empty?
-        job["trace_propagation_headers"] = Sentry.get_trace_propagation_headers
+        job["trace_propagation_headers"] ||= Sentry.get_trace_propagation_headers
         yield
       end
     end

Diff for: sentry-sidekiq/spec/sentry/sidekiq/sentry_context_middleware_spec.rb

@@ -129,5 +129,24 @@
       expect(headers["sentry-trace"]).to eq(transaction.to_sentry_trace)
       expect(headers["baggage"]).to eq(transaction.to_baggage)
     end
+
+    # sidekiq pushes the same job to the queue again from the server for schedules and retries
+    it "keeps the same trace_propagation_headers linked to the transaction when queued multiple times" do
+      client.push('queue' => 'default', 'class' => HappyWorker, 'args' => [])
+
+      # push without span transaction to simulate pushing on the server
+      Sentry.get_current_scope.clear
+      client.push(queue.first.item)
+
+      q = queue.to_a
+      expect(q.size).to be(2)
+      first_headers = q.first["trace_propagation_headers"]
+      expect(first_headers["sentry-trace"]).to eq(transaction.to_sentry_trace)
+      expect(first_headers["baggage"]).to eq(transaction.to_baggage)
+
+      second_headers = q.second["trace_propagation_headers"]
+      expect(second_headers["sentry-trace"]).to eq(transaction.to_sentry_trace)
+      expect(second_headers["baggage"]).to eq(transaction.to_baggage)
+    end
   end
 end