// Generate returns and fills a channel with *UnitStateHeartbeat objects. Objects will
// only be returned for units to which this generator is currently subscribed.
func (g *UnitStateGenerator) Generate() (<-chan *UnitStateHeartbeat, error) {
var lastSubscribed pkg.Set
if g.lastSubscribed != nil {
lastSubscribed = g.lastSubscribed.Copy()
}
subscribed := g.subscribed.Copy()
g.lastSubscribed = subscribed
reportable, err := g.mgr.GetUnitStates(subscribed)
if err != nil {
return nil, err
}
beatchan := make(chan *UnitStateHeartbeat)
go func() {
for name, us := range reportable {
us := us
beatchan <- &UnitStateHeartbeat{
Name: name,
State: us,
}
}
if lastSubscribed != nil {
// For all units that were part of the subscription list
// last time Generate ran, but are now not part of that
// list, send nil-State heartbeats to signal removal
for _, name := range lastSubscribed.Sub(subscribed).Values() {
beatchan <- &UnitStateHeartbeat{
Name: name,
}
}
}
close(beatchan)
}()
return beatchan, nil
}
