[op-conductor] resume logic improvement (ethereum-optimism#9197)

* Add conductor transition diagram

* Update sequencer active status upon resume

op-conductor/README.md

@@ -27,4 +27,12 @@ On a high level, op-conductor serves the following functions:
 3. monitor sequencer (op-node) health
 4. control loop => control sequencer (op-node) status (start / stop) based on different scenarios
 
+### Conductor State Transition
+
+![conductor state transition](./assets/op-conductor-state-transition.svg)
+
+Helpful tips:
+To better understand the graph, focus on one node at a time, understand what can be transitioned to this current state and how it can transition to other states.
+This way you could understand how we handle the state transitions.
+
 This is initial version of README, more details will be added later.

op-conductor/conductor/service.go

@@ -133,13 +133,7 @@ func (c *OpConductor) initSequencerControl(ctx context.Context) error {
 	node := sources.NewRollupClient(nc)
 	c.ctrl = client.NewSequencerControl(exec, node)
 
-	active, err := c.ctrl.SequencerActive(ctx)
-	if err != nil {
-		return errors.Wrap(err, "failed to get sequencer active status")
-	}
-	c.seqActive.Store(active)
-
-	return nil
+	return c.updateSequencerActiveStatus()
 }
 
 func (c *OpConductor) initConsensus(ctx context.Context) error {
@@ -358,6 +352,11 @@ func (oc *OpConductor) Pause(ctx context.Context) error {
 
 // Resume resumes the control loop of OpConductor.
 func (oc *OpConductor) Resume(ctx context.Context) error {
+	err := oc.updateSequencerActiveStatus()
+	if err != nil {
+		return errors.Wrap(err, "cannot resume because failed to get sequencer active status")
+	}
+
 	select {
 	case oc.resumeCh <- struct{}{}:
 		<-oc.resumeDoneCh
@@ -612,3 +611,12 @@ func (oc *OpConductor) startSequencer() error {
 	oc.seqActive.Store(true)
 	return nil
 }
+
+func (oc *OpConductor) updateSequencerActiveStatus() error {
+	active, err := oc.ctrl.SequencerActive(oc.shutdownCtx)
+	if err != nil {
+		return errors.Wrap(err, "failed to get sequencer active status")
+	}
+	oc.seqActive.Store(active)
+	return nil
+}

op-conductor/conductor/service_test.go

@@ -175,6 +175,7 @@ func (s *OpConductorTestSuite) TestControlLoop1() {
 	s.healthUpdateCh <- true
 
 	// Resume
+	s.ctrl.EXPECT().SequencerActive(mock.Anything).Return(false, nil)
 	err = s.conductor.Resume(s.ctx)
 	s.NoError(err)
 	s.False(s.conductor.Paused())
@@ -200,6 +201,7 @@ func (s *OpConductorTestSuite) TestControlLoop2() {
 	s.True(s.conductor.Paused())
 
 	// Resume
+	s.ctrl.EXPECT().SequencerActive(mock.Anything).Return(false, nil)
 	err = s.conductor.Resume(s.ctx)
 	s.NoError(err)
 	s.False(s.conductor.Paused())