engine: Create a resource kind+name specific stateful store

This adds a meta state store that is preserved between graph switches if
the kind and name match. This is useful so that rapid graph changes
don't necessarily reset their retry count if they've only changed one
resource field.

engine/metaparams.go

@@ -36,6 +36,7 @@ var DefaultMetaParams = &MetaParams{
 	Poll:  0,        // defaults to watching for events
 	Limit: rate.Inf, // defaults to no limit
 	Burst: 0,        // no burst needed on an infinite rate
+	Reset: false,
 	//Sema:  []string{},
 	Rewatch: false,
 	Realize: false, // true would be more awesome, but unexpected for users
@@ -78,6 +79,15 @@ type MetaParams struct {
 	// Burst is the number of events to allow in a burst.
 	Burst int `yaml:"burst"`
 
+	// Reset causes the meta param state to reset when the resource changes.
+	// What this means is if you have a resource of a specific kind and name
+	// and in the subsequent graph it changes because one of its params
+	// changed, normally the Retry, and other params will remember their
+	// state, and you'll not reset the retry counter, however if this is
+	// true, then it will get reset. Note that any normal reset mechanisms
+	// built into retry are not affected by this.
+	Reset bool `yaml:"reset"`
+
 	// Sema is a list of semaphore ids in the form `id` or `id:count`. If
 	// you don't specify a count, then 1 is assumed. The sema of `foo` which
 	// has a count equal to 1, is different from a sema named `foo:1` which
@@ -135,6 +145,9 @@ func (obj *MetaParams) Cmp(meta *MetaParams) error {
 	if obj.Burst != meta.Burst {
 		return fmt.Errorf("values for Burst are different")
 	}
+	if obj.Reset != meta.Reset {
+		return fmt.Errorf("values for Reset are different")
+	}
 
 	if err := util.SortedStrSliceCompare(obj.Sema, meta.Sema); err != nil {
 		return errwrap.Wrapf(err, "values for Sema are different")
@@ -182,6 +195,7 @@ func (obj *MetaParams) Copy() *MetaParams {
 		Poll:    obj.Poll,
 		Limit:   obj.Limit, // FIXME: can we copy this type like this? test me!
 		Burst:   obj.Burst,
+		Reset:   obj.Reset,
 		Sema:    sema,
 		Rewatch: obj.Rewatch,
 		Realize: obj.Realize,
@@ -202,3 +216,15 @@ func (obj *MetaParams) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	*obj = MetaParams(raw) // restore from indirection with type conversion!
 	return nil
 }
+
+// MetaState is some local meta param state that is saved between resources of
+// the same kind+name unique ID. Even though the vertex/resource pointer might
+// change during a graph switch (because the params changed) we might be
+// logically referring to the same resource, and we might want to preserve some
+// data across that switch. The common example is the resource retry count. If a
+// resource failed three times, and we had a limit of five before it would be a
+// permanent failure, then we don't want to reset this counter just because we
+// changed a parameter (field) of the resource. This doesn't mean we don't want
+// to ever reset these counts. For that, flip on the reset meta param.
+type MetaState struct {
+}