feat: add a constant error for demote primary stall

Signed-off-by: Manan Gupta <[email protected]>

go/vt/vterrors/code.go

@@ -102,6 +102,7 @@ var (
 	VT09028 = errorWithState("VT09028", vtrpcpb.Code_FAILED_PRECONDITION, CTERecursiveForbiddenJoinOrder, "In recursive query block of Recursive Common Table Expression '%s', the recursive table must neither be in the right argument of a LEFT JOIN, nor be forced to be non-first with join order hints", "")
 	VT09029 = errorWithState("VT09029", vtrpcpb.Code_FAILED_PRECONDITION, CTERecursiveRequiresSingleReference, "In recursive query block of Recursive Common Table Expression %s, the recursive table must be referenced only once, and not in any subquery", "")
 	VT09030 = errorWithState("VT09030", vtrpcpb.Code_FAILED_PRECONDITION, CTEMaxRecursionDepth, "Recursive query aborted after 1000 iterations.", "")
+	VT09031 = errorWithoutState("VT09031", vtrpcpb.Code_FAILED_PRECONDITION, "Failed to complete primary demotion", "")
 
 	VT10001 = errorWithoutState("VT10001", vtrpcpb.Code_ABORTED, "foreign key constraints are not allowed", "Foreign key constraints are not allowed, see https://vitess.io/blog/2021-06-15-online-ddl-why-no-fk/.")
 	VT10002 = errorWithoutState("VT10002", vtrpcpb.Code_ABORTED, "atomic distributed transaction not allowed: %s", "The distributed transaction cannot be committed. A rollback decision is taken.")
@@ -192,6 +193,8 @@ var (
 		VT09027,
 		VT09028,
 		VT09029,
+		VT09030,
+		VT09031,
 		VT10001,
 		VT10002,
 		VT12001,

go/vt/vttablet/tabletserver/state_manager.go

@@ -718,7 +718,7 @@ func (sm *stateManager) Broadcast() {
 	lag, err := sm.refreshReplHealthLocked()
 	if sm.demotePrimaryStalled {
 		// If we are stalled while demoting primary, we should send an error for it.
-		err = vterrors.Errorf(vtrpcpb.Code_FAILED_PRECONDITION, "Failed to complete primary demotion")
+		err = vterrors.VT09031()
 	}
 	sm.hs.ChangeState(sm.target.TabletType, sm.ptsTimestamp, lag, err, sm.isServingLocked())
 }