consul: support WithServiceResolver option (#1693)

* consul: add endpoints resolver option

* consul: resolver []*api.ServiceEntry -> []*registry.ServiceInstance

* consul: rename Resolver -> ServiceResolver

contrib/registry/consul/client.go

@@ -18,38 +18,29 @@ type Client struct {
 	cli    *api.Client
 	ctx    context.Context
 	cancel context.CancelFunc
+
+	// resolve service entry endpoints
+	resolver ServiceResolver
 }
 
 // NewClient creates consul client
 func NewClient(cli *api.Client) *Client {
-	c := &Client{cli: cli}
+	c := &Client{cli: cli, resolver: defaultResolver}
 	c.ctx, c.cancel = context.WithCancel(context.Background())
 	return c
 }
 
-// Service get services from consul
+func defaultResolver(_ context.Context, entries []*api.ServiceEntry) []*registry.ServiceInstance {
-func (d *Client) Service(ctx context.Context, service string, index uint64, passingOnly bool) ([]*registry.ServiceInstance, uint64, error) {
+	services := make([]*registry.ServiceInstance, 0, len(entries))
-	opts := &api.QueryOptions{
-		WaitIndex: index,
-		WaitTime:  time.Second * 55,
-	}
-	opts = opts.WithContext(ctx)
-	entries, meta, err := d.cli.Health().Service(service, "", passingOnly, opts)
-	if err != nil {
-		return nil, 0, err
-	}
-
-	services := make([]*registry.ServiceInstance, 0)
-
 	for _, entry := range entries {
 		var version string
 		for _, tag := range entry.Service.Tags {
-			strs := strings.SplitN(tag, "=", 2)
+			ss := strings.SplitN(tag, "=", 2)
-			if len(strs) == 2 && strs[0] == "version" {
+			if len(ss) == 2 && ss[0] == "version" {
-				version = strs[1]
+				version = ss[1]
 			}
 		}
-		var endpoints []string
+		var endpoints []string //nolint:prealloc
 		for scheme, addr := range entry.Service.TaggedAddresses {
 			if scheme == "lan_ipv4" || scheme == "wan_ipv4" || scheme == "lan_ipv6" || scheme == "wan_ipv6" {
 				continue
@@ -64,11 +55,29 @@ func (d *Client) Service(ctx context.Context, service string, index uint64, pass
 			Endpoints: endpoints,
 		})
 	}
-	return services, meta.LastIndex, nil
+
+	return services
 }
 
-// Register register service instacen to consul
+// ServiceResolver is used to resolve service endpoints
-func (d *Client) Register(ctx context.Context, svc *registry.ServiceInstance, enableHealthCheck bool) error {
+type ServiceResolver func(ctx context.Context, entries []*api.ServiceEntry) []*registry.ServiceInstance
+
+// Service get services from consul
+func (c *Client) Service(ctx context.Context, service string, index uint64, passingOnly bool) ([]*registry.ServiceInstance, uint64, error) {
+	opts := &api.QueryOptions{
+		WaitIndex: index,
+		WaitTime:  time.Second * 55,
+	}
+	opts = opts.WithContext(ctx)
+	entries, meta, err := c.cli.Health().Service(service, "", passingOnly, opts)
+	if err != nil {
+		return nil, 0, err
+	}
+	return c.resolver(ctx, entries), meta.LastIndex, nil
+}
+
+// Register register service instance to consul
+func (c *Client) Register(_ context.Context, svc *registry.ServiceInstance, enableHealthCheck bool) error {
 	addresses := make(map[string]api.ServiceAddress)
 	checkAddresses := make([]string, 0, len(svc.Endpoints))
 	for _, endpoint := range svc.Endpoints {
@@ -103,7 +112,7 @@ func (d *Client) Register(ctx context.Context, svc *registry.ServiceInstance, en
 			})
 		}
 	}
-	err := d.cli.Agent().ServiceRegister(asr)
+	err := c.cli.Agent().ServiceRegister(asr)
 	if err != nil {
 		return err
 	}
@@ -113,8 +122,8 @@ func (d *Client) Register(ctx context.Context, svc *registry.ServiceInstance, en
 		for {
 			select {
 			case <-ticker.C:
-				_ = d.cli.Agent().UpdateTTL("service:"+svc.ID, "pass", "pass")
+				_ = c.cli.Agent().UpdateTTL("service:"+svc.ID, "pass", "pass")
-			case <-d.ctx.Done():
+			case <-c.ctx.Done():
 				return
 			}
 		}
@@ -123,7 +132,7 @@ func (d *Client) Register(ctx context.Context, svc *registry.ServiceInstance, en
 }
 
 // Deregister deregister service by service ID
-func (d *Client) Deregister(ctx context.Context, serviceID string) error {
+func (c *Client) Deregister(_ context.Context, serviceID string) error {
-	d.cancel()
+	c.cancel()
-	return d.cli.Agent().ServiceDeregister(serviceID)
+	return c.cli.Agent().ServiceDeregister(serviceID)
 }

contrib/registry/consul/registry.go

@@ -26,6 +26,15 @@ func WithHealthCheck(enable bool) Option {
 	}
 }
 
+// WithServiceResolver with endpoint function option.
+func WithServiceResolver(fn ServiceResolver) Option {
+	return func(o *Registry) {
+		if o.cli != nil {
+			o.cli.resolver = fn
+		}
+	}
+}
+
 // Config is consul registry config
 type Config struct {
 	*api.Config