add basic discovery client

discovery/client.go

@@ -0,0 +1,40 @@
+package discovery
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strings"
+)
+
+const DISCOVERY_URL = "https://discovery-stage.hub.docker.com/v1"
+
+// FetchSlaves returns the slaves for the discovery service at the specified endpoint
+func FetchSlaves(token string) ([]string, error) {
+	resp, err := http.Get(fmt.Sprintf("%s/%s/%s", DISCOVERY_URL, "clusters", token))
+	if err != nil {
+		return nil, err
+	}
+
+	if resp.Body != nil {
+		defer resp.Body.Close()
+	}
+
+	var addrs []string
+	if resp.StatusCode == http.StatusOK {
+		if err := json.NewDecoder(resp.Body).Decode(&addrs); err != nil {
+			return nil, err
+		}
+	}
+
+	return addrs, nil
+}
+
+// RegisterSlave adds a new slave identified by the slaveID into the discovery service
+// the default TTL is 30 secs
+func RegisterSlave(addr, token string) error {
+	buf := strings.NewReader(addr)
+
+	_, err := http.Post(fmt.Sprintf("%s/%s/%s", DISCOVERY_URL, "clusters", token), "application/json", buf)
+	return err
+}

discovery/client_test.go

@@ -0,0 +1,27 @@
+package discovery
+
+import "testing"
+
+func TestRegisterLocal(t *testing.T) {
+	expected := "127.0.0.1:2675"
+	if err := RegisterSlave(expected, "TEST_TOKEN"); err != nil {
+		t.Fatal(err)
+	}
+
+	addrs, err := FetchSlaves("TEST_TOKEN")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if len(addrs) != 1 {
+		t.Fatalf("expected addr len == 1, got len = %d", len(addrs))
+	}
+
+	if addrs[0] != expected {
+		t.Fatalf("expected addr %q but received %q", expected, addrs[0])
+	}
+
+	if err = RegisterSlave(expected, "TEST_TOKEN"); err != nil {
+		t.Fatal(err)
+	}
+}