sd - ActiveState ActiveGo 1.8

Package sd

import ""

Overview ▾

Package sd provides utilities related to service discovery. That includes the client-side loadbalancer pattern, where a microservice subscribes to a service discovery system in order to reach remote instances; as well as the registrator pattern, where a microservice registers itself in a service discovery system. Implementations are provided for most common systems.

type Factory

Factory is a function that converts an instance string (e.g. host:port) to a specific endpoint. Instances that provide multiple endpoints require multiple factories. A factory also returns an io.Closer that's invoked when the instance goes away and needs to be cleaned up. Factories may return nil closers.

Users are expected to provide their own factory functions that assume specific transports, or can deduce transports by parsing the instance string.

type Factory func(instance string) (endpoint.Endpoint, io.Closer, error)

type FixedSubscriber

FixedSubscriber yields a fixed set of services.

type FixedSubscriber []endpoint.Endpoint

func (FixedSubscriber) Endpoints

func (s FixedSubscriber) Endpoints() ([]endpoint.Endpoint, error)

Endpoints implements Subscriber.

type Registrar

Registrar registers instance information to a service discovery system when an instance becomes alive and healthy, and deregisters that information when the service becomes unhealthy or goes away.

Registrar implementations exist for various service discovery systems. Note that identifying instance information (e.g. host:port) must be given via the concrete constructor; this interface merely signals lifecycle changes.

type Registrar interface {

type Subscriber

Subscriber listens to a service discovery system and yields a set of identical endpoints on demand. An error indicates a problem with connectivity to the service discovery system, or within the system itself; a subscriber may yield no endpoints without error.

type Subscriber interface {
    Endpoints() ([]endpoint.Endpoint, error)


Name Synopsis
consul Package consul provides subscriber and registrar implementations for Consul.
dnssrv Package dnssrv provides a subscriber implementation for DNS SRV records.
etcd Package etcd provides a Subscriber and Registrar implementation for etcd.
lb Package lb implements the client-side load balancer pattern.
zk Package zk provides subscriber and registrar implementations for ZooKeeper.