initial commit

discovery.go

@@ -0,0 +1,127 @@
+package discovery
+
+import (
+	"context"
+	"encoding/json"
+	"github.com/coreos/etcd/clientv3"
+	"github.com/google/uuid"
+	"path"
+)
+
+type Registry struct {
+	client *clientv3.Client
+	path   string
+}
+
+func New(endpoints []string) (*Registry, error) {
+	client, err := clientv3.New(clientv3.Config{
+		Endpoints: endpoints,
+	})
+
+	if err != nil {
+		return nil, err
+	}
+
+	return &Registry{
+		client: client,
+	}, nil
+}
+
+func (r *Registry) Register(ctx context.Context, service string, host Host) error {
+	resp, err := r.client.Grant(context.Background(), 30)
+
+	if err != nil {
+		return err
+	}
+
+	if host.UUID == "" {
+		host.UUID = uuid.New().String()
+	}
+
+	b, err := json.Marshal(host)
+
+	if err != nil {
+		return err
+	}
+
+	key := path.Join(r.path, service, host.UUID)
+
+	_, err = r.client.Put(context.Background(), key, string(b), clientv3.WithLease(resp.ID))
+
+	if err != nil {
+		return err
+	}
+
+	ch, err := r.client.KeepAlive(ctx, resp.ID)
+
+	if err != nil {
+		return err
+	}
+
+	go func() {
+		for {
+			select {
+			case ka := <-ch:
+				if ka == nil {
+					return
+				}
+
+				// Removed
+			}
+		}
+	}()
+
+	return nil
+}
+
+func (r *Registry) Get(service string) ([]Host, error) {
+	res, err := r.client.Get(context.Background(), path.Join(r.path, service), clientv3.WithPrefix())
+
+	if err != nil {
+		return nil, err
+	}
+
+	var host Host
+
+	hosts := make([]Host, len(res.Kvs))
+
+	for i, kv := range res.Kvs {
+		host = Host{}
+
+		if err = json.Unmarshal(kv.Value, &host); err != nil {
+			continue
+		}
+
+		hosts[i] = host
+	}
+
+	return hosts, nil
+}
+
+func (r *Registry) Watch(service string) (chan Host, chan string) {
+	ch := r.client.Watch(context.Background(), path.Join(r.path, service), clientv3.WithPrefix())
+
+	upChan := make(chan Host)
+	downChan := make(chan string)
+
+	go func() {
+		for resp := range ch {
+			for _, e := range resp.Events {
+				if e.Type == clientv3.EventTypeDelete {
+					// Removed
+					downChan <- string(e.Kv.Key)
+				} else if e.IsCreate() || e.IsModify() {
+					host := Host{}
+
+					if err := json.Unmarshal(e.Kv.Value, &host); err != nil {
+						continue
+					}
+
+					upChan <- host
+				}
+			}
+		}
+	}()
+
+	return upChan, downChan
+}

go.mod

@@ -0,0 +1,8 @@
+module meow.tf/go/service-discovery
+
+go 1.15
+
+require (
+	github.com/coreos/etcd v3.3.13+incompatible
+	github.com/google/uuid v1.1.1
+)

host.go

@@ -0,0 +1,14 @@
+package discovery
+
+type Ports map[string]string
+
+type Host struct {
+	// UUID is the host registration's UUID
+	UUID string `json:"uuid"`
+	// Hostname is the primary hostname or ip of the host.
+	Hostname string `json:"hostname"`
+	// PrivateHostname is the private/local network hostname or ip of the host.
+	PrivateHostname string `json:"private_hostname,omitempty"`
+	// Ports defines which ports the services on the host use.
+	Ports Ports `json:"ports"`
+}