Trigger hook for upgrade series on build.

worker/uniter/hook/hook.go

@@ -48,7 +48,7 @@ func (hi Info) Validate() error {
 		}
 		fallthrough
 	case hooks.Install, hooks.Start, hooks.ConfigChanged, hooks.UpgradeCharm, hooks.Stop, hooks.RelationBroken,
-		hooks.CollectMetrics, hooks.MeterStatusChanged, hooks.UpdateStatus:
+		hooks.CollectMetrics, hooks.MeterStatusChanged, hooks.UpdateStatus, hooks.UpgradeSeriesPrepare:
 		return nil
 	case hooks.Action:
 		return fmt.Errorf("hooks.Kind Action is deprecated")

worker/uniter/resolver.go

@@ -278,6 +278,11 @@ func (s *uniterResolver) nextOp(
 		return opFactory.NewRunHook(hook.Info{Kind: hooks.ConfigChanged})
 	}
 
+	if localState.UpgradeSeriesStatus != remoteState.UpgradeSeriesStatus &&
+		remoteState.UpgradeSeriesStatus == "preparing" {
+		return opFactory.NewRunHook(hook.Info{Kind: hooks.UpgradeSeriesPrepare})
+	}
+
 	op, err := s.config.Relations.NextOp(localState, remoteState, opFactory)
 	if errors.Cause(err) != resolver.ErrNoOperation {
 		return op, err

worker/uniter/resolver/interface.go

@@ -98,4 +98,8 @@ type LocalState struct {
 	// Series is the current series running on the unit from remotestate.Snapshot
 	// for which a config-changed hook has been committed.
 	Series string
+
+	// UpgradeSeriesStatus is the current state of any currently running
+	// series upgrade or the empty string if no series upgrade has been started.
+	UpgradeSeriesStatus string
 }

worker/uniter/resolver_test.go

@@ -126,6 +126,25 @@ func (s *resolverSuite) TestSeriesChanged(c *gc.C) {
 	c.Assert(op.String(), gc.Equals, "run config-changed hook")
 }
 
+func (s *resolverSuite) TestUpgradeSeriesStatusChanged(c *gc.C) {
+	localState := resolver.LocalState{
+		CharmModifiedVersion: s.charmModifiedVersion,
+		CharmURL:             s.charmURL,
+		Series:               s.charmURL.Series,
+		UpgradeSeriesStatus:  "",
+		State: operation.State{
+			Kind:      operation.Continue,
+			Installed: true,
+			Started:   true,
+		},
+	}
+	s.remoteState.Series = s.charmURL.Series
+	s.remoteState.UpgradeSeriesStatus = "preparing"
+	op, err := s.resolver.NextOp(localState, s.remoteState, s.opFactory)
+	c.Assert(err, jc.ErrorIsNil)
+	c.Assert(op.String(), gc.Equals, "run upgrade-series-prepare hook")
+}
+
 func (s *resolverSuite) TestSeriesChangedBlank(c *gc.C) {
 	localState := resolver.LocalState{
 		CharmModifiedVersion: s.charmModifiedVersion,