All microservices on the Microbus subscribe to handle control messages on the reserved port :888 in addition to any subscriptions they create for their own use case.
The :888/ping endpoint enables runtime discovery of microservices. The ping handler is subscribed to both the hostname of the service and to the special host all, allowing the discovery of replicas of a specific microservice, or of all microservices.
To discover all instances of www.example.com using the Publish method of the connector:
ch := con.Publish(r.Context(), pub.GET("https://www.example.com:888/ping"))
for r := range ch {
res, err := r.Get()
if err != nil {
return errors.Trace(err)
}
fromHost := frame.Of(res).FromHost()
fromID := frame.Of(res).FromID()
}
Or use the controlapi.Client that abstracts the internals:
ch := controlapi.NewMulticastClient(svc).ForHost("www.example.com").Ping(ctx)
for r := range ch {
fromHost := frame.Of(r.HTTPResponse).FromHost()
fromID := frame.Of(r.HTTPResponse).FromID()
}
To discover instances of all microservices replace the hostname www.example.com with the special hostname all:
ch := con.Publish(r.Context(), pub.GET("https://all:888/ping"))
Or with controlapi:
ch := controlapi.NewMulticastClient(svc).ForHost("all").Ping(ctx)
The :888/config-refresh endpoint indicates to the microservice to contact the configurator to refetch the values of its config properties.
The :888/trace endpoint indicates to the microservice to export all tracing spans belonging to the requested trace ID (as indicated by the id argument) to the OLTP collector.