1 package sd 2 3 // Event represents a push notification generated from the underlying service discovery 4 // implementation. It contains either a full set of available resource instances, or 5 // an error indicating some issue with obtaining information from discovery backend. 6 // Examples of errors may include loosing connection to the discovery backend, or 7 // trying to look up resource instances using an incorrectly formatted key. 8 // After receiving an Event with an error the listenter should treat previously discovered 9 // resource instances as stale (although it may choose to continue using them). 10 // If the Instancer is able to restore connection to the discovery backend it must push 11 // another Event with the current set of resource instances. 12 type Event struct { 13 Instances []string 14 Err error 15 } 16 17 // Instancer listens to a service discovery system and notifies registered 18 // observers of changes in the resource instances. Every event sent to the channels 19 // contains a complete set of instances known to the Instancer. That complete set is 20 // sent immediately upon registering the channel, and on any future updates from 21 // discovery system. 22 type Instancer interface { 23 Register(chan<- Event) 24 Deregister(chan<- Event) 25 Stop() 26 } 27 28 // FixedInstancer yields a fixed set of instances. 29 type FixedInstancer []string 30 31 // Register implements Instancer. 32 func (d FixedInstancer) Register(ch chan<- Event) { ch <- Event{Instances: d} } 33 34 // Deregister implements Instancer. 35 func (d FixedInstancer) Deregister(ch chan<- Event) {} 36 37 // Stop implements Instancer. 38 func (d FixedInstancer) Stop() {} 39