client: resolver updates svc addresses periodically

client/resolver/eru/builder.go

@@ -0,0 +1,19 @@
+package eru
+
+import "google.golang.org/grpc/resolver"
+
+type eruResolverBuilder struct{}
+
+func init() {
+	resolver.Register(&eruResolverBuilder{})
+}
+
+// Scheme for interface
+func (b *eruResolverBuilder) Scheme() string {
+	return "eru"
+}
+
+// Build for interface
+func (b *eruResolverBuilder) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOptions) (resolver.Resolver, error) {
+	return New(cc, target.Endpoint), nil
+}

client/resolver/eru/resolver.go

@@ -0,0 +1,65 @@
+package eru
+
+import (
+	"context"
+
+	"github.com/projecteru2/core/client/service_discovery"
+	log "github.com/sirupsen/logrus"
+	"google.golang.org/grpc/resolver"
+)
+
+type eruResolver struct {
+	cc        resolver.ClientConn
+	cancel    context.CancelFunc
+	discovery service_discovery.ServiceDiscovery
+}
+
+func New(cc resolver.ClientConn, endpoint string) *eruResolver {
+	r := &eruResolver{
+		cc:        cc,
+		discovery: service_discovery.New(endpoint),
+	}
+	go r.sync()
+	return r
+}
+
+// ResolveNow for interface
+func (r *eruResolver) ResolveNow(_ resolver.ResolveNowOptions) {}
+
+// Close for interface
+func (r *eruResolver) Close() {
+	r.cancel()
+}
+
+func (r *eruResolver) sync() {
+	log.Info("[eruResolver] start sync service discovery")
+	ctx, cancel := context.WithCancel(context.Background())
+	r.cancel = cancel
+	defer cancel()
+
+	ch, err := r.discovery.Watch(ctx)
+	if err != nil {
+		log.Errorf("[eruResolver] failed to watch service status: %v", err)
+		return
+	}
+	for {
+		select {
+		case <-ctx.Done():
+			log.Errorf("[eruResolver] watch interrupted: %v", ctx.Err())
+			break
+		case endpoints, ok := <-ch:
+			if !ok {
+				log.Error("[eruResolver] watch closed")
+				break
+			}
+
+			var addresses []resolver.Address
+			log.Debugf("[eruResolver] update state: %v", endpoints)
+			for _, ep := range endpoints {
+				addresses = append(addresses, resolver.Address{Addr: ep})
+			}
+			r.cc.UpdateState(resolver.State{Addresses: addresses})
+		}
+	}
+
+}

client/resolver/static/builder.go

@@ -0,0 +1,19 @@
+package static
+
+import "google.golang.org/grpc/resolver"
+
+type staticResolverBuilder struct{}
+
+func init() {
+	resolver.Register(&staticResolverBuilder{})
+}
+
+// Scheme for interface
+func (b *staticResolverBuilder) Scheme() string {
+	return "static"
+}
+
+// Build for interface
+func (b *staticResolverBuilder) Build(target resolver.Target, cc resolver.ClientConn, opts resolver.BuildOptions) (resolver.Resolver, error) {
+	return New(cc, target.Endpoint), nil
+}

client/resolver/static/resolver.go

@@ -0,0 +1,30 @@
+package static
+
+import (
+	"strings"
+
+	"google.golang.org/grpc/resolver"
+)
+
+type staticResolver struct {
+	addresses []resolver.Address
+	cc        resolver.ClientConn
+}
+
+func New(cc resolver.ClientConn, endpoints string) *staticResolver {
+	var addresses []resolver.Address
+	for _, ep := range strings.Split(endpoints, ",") {
+		addresses = append(addresses, resolver.Address{Addr: ep})
+	}
+	cc.UpdateState(resolver.State{Addresses: addresses})
+	return &staticResolver{
+		cc:        cc,
+		addresses: addresses,
+	}
+}
+
+// ResolveNow for interface
+func (r *staticResolver) ResolveNow(_ resolver.ResolveNowOptions) {}
+
+// Close for interface
+func (r *staticResolver) Close() {}