invocation

type Invocation struct {
	//service's ip and port, it is decided in load balancer
	Endpoint string
	//specify rest,highway
	Protocol string
	//Ctx value will be send as header in transport
	Ctx                context.Context
	SourceServiceID    string
	SourceMicroService string
	MicroServiceName   string
	Version            string
	AppID              string
	//correspond struct
	SchemaID string
	//correspond struct func
	OperationID string
	Args        interface{}
	//an url path has muntil path params such as "/v2/microsvice/:id/instance/:instanceid",http client use this to format correct url
	URLPathFormat string

	Reply interface{}
	//just in local memory
	Metadata map[string]interface{}
	//loadbalancer stratery
	//Strategy loadbalancer.Strategy
	Strategy string
	Filters  []loadbalancer.Filter
}

type InvocationResponse struct {
	Status int
	Result interface{}
	Err    error
}

type ResponseCallBack func(*InvocationResponse) error