Config option for preserving no signals in the first task

Author: jeffschoner

lib/temporal/configuration.rb

@@ -18,7 +18,7 @@ class Configuration
     attr_reader :timeouts, :error_handlers, :capabilities
     attr_accessor :connection_type, :converter, :use_error_serialization_v2, :host, :port, :credentials, :identity,
                   :logger, :metrics_adapter, :namespace, :task_queue, :headers, :search_attributes, :header_propagators,
-                  :payload_codec, :legacy_signals
+                  :payload_codec, :legacy_signals, :no_signals_in_first_task
 
     # See https://docs.temporal.io/blog/activity-timeouts/ for general docs.
     # We want an infinite execution timeout for cron schedules and other perpetual workflows.
@@ -92,6 +92,10 @@ def initialize
       # in Temporal server 1.20, it is ignored when connected to older versions and effectively
       # treated as true.
       @legacy_signals = false
+
+      # This is a legacy behavior that is incorrect, but which existing workflow code may rely on. Only
+      # set to true until you can fix your workflow code.
+      @no_signals_in_first_task = false
     end
 
     def on_error(&block)

lib/temporal/workflow/state_manager.rb

@@ -138,7 +138,7 @@ def self.workflow_execution_started_event?(event)
 
       private
 
-      attr_reader :dispatcher, :command_tracker, :marker_ids, :side_effects, :releases
+      attr_reader :dispatcher, :command_tracker, :marker_ids, :side_effects, :releases, :config
 
       def use_signals_first(raw_events)
         if sdk_flags.include?(SDKFlags::HANDLE_SIGNALS_FIRST)
@@ -149,14 +149,14 @@ def use_signals_first(raw_events)
           true
         elsif raw_events.any? { |event| StateManager.signal_event?(event) } &&
               # If this is being played for the first time, use the configuration flag to choose
-              (!replay? && !@config.legacy_signals) &&
+              (!replay? && !config.legacy_signals) &&
               # In order to preserve determinism, the server must support SDK metadata to order signals
               # first. This is checked last because it will result in a Temporal server call the first
               # time it's called in the worker process.
-              @config.capabilities.sdk_metadata
+              config.capabilities.sdk_metadata
           report_flag_used(SDKFlags::HANDLE_SIGNALS_FIRST)
 
-          if raw_events.any? { |event| StateManager.workflow_execution_started_event?(event) }
+          if raw_events.any? { |event| StateManager.workflow_execution_started_event?(event) } && !config.no_signals_in_first_task
             report_flag_used(SDKFlags::SAVE_FIRST_TASK_SIGNALS)
           end
 

spec/unit/lib/temporal/workflow/state_manager_spec.rb

@@ -154,7 +154,7 @@ class MyWorkflow < Temporal::Workflow; end
           state_manager.apply(history.next_window)
         end
       end
-      
+
       context 'replaying with SAVE_FIRST_TASK_SIGNALS sdk flag' do
         let(:sdk_flags) do [
             Temporal::Workflow::SDKFlags::HANDLE_SIGNALS_FIRST,
@@ -385,6 +385,55 @@ def test_order(signal_first)
         end
       end
     end
+
+    context 'not replaying with a signal in the first workflow task' do
+      let(:signal_entry) { Fabricate(:api_workflow_execution_signaled_event, event_id: 2) }
+      let(:history) do
+        Temporal::Workflow::History.new(
+          [
+            Fabricate(:api_workflow_execution_started_event, event_id: 1),
+            signal_entry,
+            Fabricate(:api_workflow_task_scheduled_event, event_id: 3)
+          ]
+        )
+      end
+
+      def test_order_one_task(*expected_sdk_flags)
+        allow(connection).to receive(:get_system_info).and_return(system_info)
+        signaled = false
+
+        dispatcher.register_handler(
+          Temporal::Workflow::Signal.new(
+            signal_entry.workflow_execution_signaled_event_attributes.signal_name
+          ),
+          'signaled'
+        ) do
+          signaled = true
+        end
+
+        state_manager.apply(history.next_window)
+        expect(state_manager.new_sdk_flags_used).to eq(Set.new(expected_sdk_flags))
+        expect(signaled).to eq(true)
+      end
+
+      context 'default config' do
+        let(:config) { Temporal::Configuration.new }
+
+        it 'signal first' do
+          test_order_one_task(
+            Temporal::Workflow::SDKFlags::HANDLE_SIGNALS_FIRST,
+            Temporal::Workflow::SDKFlags::SAVE_FIRST_TASK_SIGNALS
+          )
+        end
+      end
+
+      context 'no signals in first task enabled' do
+        let(:config) { Temporal::Configuration.new.tap { |c| c.no_signals_in_first_task = true } }
+        it 'signal inline' do
+          test_order_one_task(Temporal::Workflow::SDKFlags::HANDLE_SIGNALS_FIRST)
+        end
+      end
+    end
   end
 
   describe '#search_attributes' do