ringpop: add method to selfEvict from ring (#3132)

common/membership/interfaces.go

@@ -53,6 +53,10 @@ type (
 		common.Daemon
 
 		WhoAmI() (*HostInfo, error)
+		// EvictSelf evicts this member from the membership ring. After this method is
+		// called, other members will discover that this node is no longer part of the
+		// ring. This primitive is useful to carry out graceful host shutdown during deployments.
+		EvictSelf() error
 		Lookup(service string, key string) (*HostInfo, error)
 		GetResolver(service string) (ServiceResolver, error)
 		// AddListener adds a listener for this service.

common/membership/rpMonitor.go

@@ -115,6 +115,10 @@ func (rpo *ringpopMonitor) WhoAmI() (*HostInfo, error) {
 	return NewHostInfo(address, labels.AsMap()), nil
 }
 
+func (rpo *ringpopMonitor) EvictSelf() error {
+	return rpo.rp.SelfEvict()
+}
+
 func (rpo *ringpopMonitor) GetResolver(service string) (ServiceResolver, error) {
 	ring, found := rpo.rings[service]
 	if !found {

host/simpleMonitor.go

@@ -47,6 +47,10 @@ func (s *simpleMonitor) Start() {
 func (s *simpleMonitor) Stop() {
 }
 
+func (s *simpleMonitor) EvictSelf() error {
+	return nil
+}
+
 func (s *simpleMonitor) WhoAmI() (*membership.HostInfo, error) {
 	return s.hostInfo, nil
 }