Add a minion registry that is backed by a cloud provider.

pkg/cloudprovider/cloud.go

@@ -38,4 +38,6 @@ type TCPLoadBalancer interface {
 
 type Instances interface {
 	IPAddress(name string) (net.IP, error)
+	// Lists instances that match 'filter' which is a regular expression which must match the entire instance name
+	List(filter string) ([]string, error)
 }

pkg/cloudprovider/fake_cloud.go

@@ -18,13 +18,15 @@ package cloudprovider
 
 import (
 	"net"
+	"regexp"
 )
 
 type FakeCloud struct {
-	Exists bool
-	Err    error
-	Calls  []string
-	IP     net.IP
+	Exists   bool
+	Err      error
+	Calls    []string
+	IP       net.IP
+	Machines []string
 }
 
 func (f *FakeCloud) addCall(desc string) {
@@ -66,3 +68,14 @@ func (f *FakeCloud) IPAddress(instance string) (net.IP, error) {
 	f.addCall("ip-address")
 	return f.IP, f.Err
 }
+
+func (f *FakeCloud) List(filter string) ([]string, error) {
+	f.addCall("list")
+	result := []string{}
+	for _, machine := range f.Machines {
+		if match, _ := regexp.MatchString(filter, machine); match {
+			result = append(result, machine)
+		}
+	}
+	return result, f.Err
+}

pkg/cloudprovider/gce.go

@@ -30,9 +30,10 @@ import (
 )
 
 type GCECloud struct {
-	service   *compute.Service
-	projectID string
-	zone      string
+	service    *compute.Service
+	projectID  string
+	zone       string
+	instanceRE string
 }
 
 func getProjectAndZone() (string, string, error) {
@@ -179,3 +180,19 @@ func (gce *GCECloud) IPAddress(instance string) (net.IP, error) {
 	}
 	return ip, nil
 }
+
+func (gce *GCECloud) List(filter string) ([]string, error) {
+	listCall := gce.service.Instances.List(gce.projectID, gce.zone)
+	if len(filter) > 0 {
+		listCall = listCall.Filter("name eq " + filter)
+	}
+	res, err := listCall.Do()
+	if err != nil {
+		return nil, err
+	}
+	var instances []string
+	for _, instance := range res.Items {
+		instances = append(instances, instance.Name)
+	}
+	return instances, nil
+}