History size and suggest continue as new

examples/bin/worker

@@ -41,6 +41,7 @@ worker.register_workflow(CancellingTimerWorkflow)
 worker.register_workflow(CheckWorkflow)
 worker.register_workflow(ChildWorkflowTimeoutWorkflow)
 worker.register_workflow(ChildWorkflowTerminatedWorkflow)
+worker.register_workflow(ContinueAsNewWorkflow)
 worker.register_workflow(FailingActivitiesWorkflow)
 worker.register_workflow(FailingWorkflow)
 worker.register_workflow(HandlingStructuredErrorWorkflow)

examples/spec/integration/continue_as_new_spec.rb

@@ -1,3 +1,4 @@
+require 'workflows/continue_as_new_workflow'
 require 'workflows/loop_workflow'
 
 describe LoopWorkflow do
@@ -47,4 +48,46 @@
     expect(final_result[:memo]).to eq(memo)
     expect(final_result[:headers]).to eq(headers)
   end
+
+  it 'uses history bytes size to continue as new' do
+    workflow_id = SecureRandom.uuid
+    # 7 activity invocations produce about 10,000 bytes of history. This should
+    # result in one continue as new with 7 activities in the first and 3 in the
+    # second run.
+    run_id = Temporal.start_workflow(
+      ContinueAsNewWorkflow,
+      10, # hello count
+      10_000, # max bytes limit
+      options: {
+        workflow_id: workflow_id,
+        timeouts: {
+          execution: 60,
+          run: 20
+        }
+      },
+    )
+
+    # First run will throw because it continued as new
+    next_run_id = nil
+    expect do
+      Temporal.await_workflow_result(
+        ContinueAsNewWorkflow,
+        workflow_id: workflow_id,
+        run_id: run_id,
+      )
+    end.to raise_error(Temporal::WorkflowRunContinuedAsNew) do |error|
+      next_run_id = error.new_run_id
+    end
+
+    expect(next_run_id).to_not eq(nil)
+
+    # Second run will not throw because it returns rather than continues as new.
+    final_result = Temporal.await_workflow_result(
+      ContinueAsNewWorkflow,
+      workflow_id: workflow_id,
+      run_id: next_run_id,
+    )
+
+    expect(final_result[:runs]).to eq(2)
+  end
 end

examples/workflows/continue_as_new_workflow.rb

@@ -0,0 +1,19 @@
+require 'activities/hello_world_activity'
+
+# Demonstrates how to use history_size to determine when to continue as new
+class ContinueAsNewWorkflow < Temporal::Workflow
+  def execute(hello_count, bytes_max, run = 1)
+    while hello_count.positive? && workflow.history_size.bytes < bytes_max
+      HelloWorldActivity.execute!("Alice Long#{'long' * 100}name")
+      hello_count -= 1
+    end
+
+    workflow.logger.info("Workflow history size: #{workflow.history_size}, remaining hellos: #{hello_count}")
+
+    return workflow.continue_as_new(hello_count, bytes_max, run + 1) if hello_count.positive?
+
+    {
+      runs: run
+    }
+  end
+end

lib/temporal/workflow/context.rb

@@ -67,6 +67,12 @@ def has_release?(release_name)
         state_manager.release?(release_name.to_s)
       end
 
+      # Returns information about the workflow run's history up to this point. This can be used to
+      # determine when to continue as new.
+      def history_size
+        state_manager.history_size
+      end
+
       def execute_activity(activity_class, *input, **args)
         options = args.delete(:options) || {}
         input << args unless args.empty?

lib/temporal/workflow/history/size.rb

@@ -0,0 +1,11 @@
+module Temporal
+  class Workflow
+    class History
+      Size = Struct.new(
+        :bytes, # integer, total number of bytes used
+        :events, # integer, total number of history events used
+        :suggest_continue_as_new, # boolean, true if server history length limits are being approached
+        keyword_init: true)
+    end
+  end
+end

lib/temporal/workflow/history/window.rb

@@ -5,14 +5,16 @@ module Temporal
   class Workflow
     class History
       class Window
-        attr_reader :local_time, :last_event_id, :events, :sdk_flags
+        attr_reader :local_time, :last_event_id, :events, :sdk_flags, :history_size_bytes, :suggest_continue_as_new
 
         def initialize
           @local_time = nil
           @last_event_id = nil
           @events = []
           @replay = false
           @sdk_flags = Set.new
+          @history_size_bytes = 0
+          @suggest_continue_as_new = false
         end
 
         def replay?
@@ -24,6 +26,8 @@ def add(event)
           when 'WORKFLOW_TASK_STARTED'
             @last_event_id = event.id + 1 # one for completed
             @local_time = event.timestamp
+            @history_size_bytes = event.attributes.history_size_bytes
+            @suggest_continue_as_new = event.attributes.suggest_continue_as_new
           when 'WORKFLOW_TASK_FAILED', 'WORKFLOW_TASK_TIMED_OUT'
             @last_event_id = nil
             @local_time = nil

lib/temporal/workflow/state_manager.rb

@@ -3,6 +3,7 @@
 require 'temporal/workflow/command'
 require 'temporal/workflow/command_state_machine'
 require 'temporal/workflow/history/event_target'
+require 'temporal/workflow/history/size'
 require 'temporal/concerns/payloads'
 require 'temporal/workflow/errors'
 require 'temporal/workflow/sdk_flags'
@@ -90,6 +91,8 @@ def apply(history_window)
         @local_time = history_window.local_time
         @last_event_id = history_window.last_event_id
         history_window.sdk_flags.each { |flag| sdk_flags.add(flag) }
+        @history_size_bytes = history_window.history_size_bytes
+        @suggest_continue_as_new = history_window.suggest_continue_as_new
 
         order_events(history_window.events).each do |event|
           apply_event(event)
@@ -116,6 +119,14 @@ def self.signal_event?(event)
         event.type == 'WORKFLOW_EXECUTION_SIGNALED'
       end
 
+      def history_size
+        History::Size.new(
+          events: @last_event_id,
+          bytes: @history_size_bytes,
+          suggest_continue_as_new: @suggest_continue_as_new
+        ).freeze
+      end
+
       private
 
       attr_reader :dispatcher, :command_tracker, :marker_ids, :side_effects, :releases, :sdk_flags

spec/fabricators/grpc/history_event_fabricator.rb

@@ -62,12 +62,15 @@ class TestSerializer
 end
 
 Fabricator(:api_workflow_task_started_event, from: :api_history_event) do
+  transient :history_size_bytes, :suggest_continue_as_new
   event_type { Temporalio::Api::Enums::V1::EventType::EVENT_TYPE_WORKFLOW_TASK_STARTED }
   workflow_task_started_event_attributes do |attrs|
     Temporalio::Api::History::V1::WorkflowTaskStartedEventAttributes.new(
       scheduled_event_id: attrs[:event_id] - 1,
       identity: 'test-worker@test-host',
-      request_id: SecureRandom.uuid
+      request_id: SecureRandom.uuid,
+      history_size_bytes: attrs[:history_size_bytes],
+      suggest_continue_as_new: attrs[:suggest_continue_as_new]
     )
   end
 end

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

@@ -302,6 +302,40 @@ def test_order(signal_first)
     end
   end
 
+  describe '#history_size' do
+    let(:config) { Temporal::Configuration.new }
+    let(:history_size_bytes) { 27 }
+    let(:suggest_continue_as_new) { true }
+    let(:start_workflow_execution_event) { Fabricate(:api_workflow_execution_started_event) }
+    let(:workflow_task_scheduled_event) { Fabricate(:api_workflow_task_scheduled_event, event_id: 2) }
+    let(:workflow_task_started_event) do
+      Fabricate(
+        :api_workflow_task_started_event,
+        event_id: 3,
+        history_size_bytes: history_size_bytes,
+        suggest_continue_as_new: suggest_continue_as_new)
+    end
+
+    it 'has correct event count' do
+      state_manager = described_class.new(Temporal::Workflow::Dispatcher.new, config)
+
+      window = Temporal::Workflow::History::Window.new
+      window.add(Temporal::Workflow::History::Event.new(start_workflow_execution_event))
+      window.add(Temporal::Workflow::History::Event.new(workflow_task_scheduled_event))
+      window.add(Temporal::Workflow::History::Event.new(workflow_task_started_event))
+
+      state_manager.apply(window)
+
+      expect(state_manager.history_size).to eq(
+        Temporal::Workflow::History::Size.new(
+          events: 4, # comes from event id of started + 1
+          bytes: history_size_bytes,
+          suggest_continue_as_new: suggest_continue_as_new
+        )
+      )
+    end
+  end
+
   describe '#search_attributes' do
     let(:initial_search_attributes) do
       {