// Update modifies the queue such that the hook.Info values it sends will
// reflect the supplied change.
func (q *liveSource) Update(change multiwatcher.RelationUnitsChange) error {
if !q.started {
q.started = true
// The first event represents the ideal final state of the system.
// If it contains any Departed notifications, it cannot be one of
// those -- most likely the watcher was not a fresh one -- and we're
// completely hosed.
if len(change.Departed) != 0 {
return errors.Errorf("hook source watcher sent bad event: %#v", change)
}
// Anyway, before we can generate actual hooks, we have to generate
// departed hooks for any previously-known members not reflected in
// the ideal state, and insert those at the head of the queue. The
// easiest way to do this is to inject a departure update for those
// missing members before processing the ideal state.
departs := multiwatcher.RelationUnitsChange{}
for unit := range q.info {
if _, found := change.Changed[unit]; !found {
departs.Departed = append(departs.Departed, unit)
}
}
q.update(departs)
}
q.update(change)
return nil
}
func (d send) event() multiwatcher.RelationUnitsChange {
ruc := multiwatcher.RelationUnitsChange{Changed: map[string]multiwatcher.UnitSettings{}}
for name, version := range d.changed {
ruc.Changed[name] = multiwatcher.UnitSettings{Version: version}
}
for _, name := range d.departed {
ruc.Departed = append(ruc.Departed, name)
}
return ruc
}