func (this *memTopics) Retain(msg *message.PublishMessage) error {
this.rmu.Lock()
defer this.rmu.Unlock()
// So apparently, at least according to the MQTT Conformance/Interoperability
// Testing, that a payload of 0 means delete the retain message.
// https://eclipse.org/paho/clients/testing/
if len(msg.Payload()) == 0 {
return this.rroot.rremove(msg.Topic())
}
return this.rroot.rinsert(msg.Topic(), msg)
}