flannel: added flannel support and helper to make dropins

fleet, flannel, and etcd all generate dropins from config.
To reduce code duplication, factor out a helper to do that.

system/env.go

@@ -19,6 +19,8 @@ package system
 import (
 	"fmt"
 	"reflect"
+
+	"github.com/coreos/coreos-cloudinit/config"
 )
 
 // dropinContents generates the contents for a drop-in unit given the config.
@@ -40,3 +42,16 @@ func dropinContents(e interface{}) string {
 	}
 	return "[Service]\n" + out
 }
+
+func dropinFromConfig(cfg interface{}, name string) []Unit {
+	content := dropinContents(cfg)
+	if content == "" {
+		return nil
+	}
+	return []Unit{{config.Unit{
+		Name:    name,
+		Runtime: true,
+		DropIn:  true,
+		Content: content,
+	}}}
+}

system/etcd.go

@@ -28,14 +28,5 @@ type Etcd struct {
 
 // Units creates a Unit file drop-in for etcd, using any configured options.
 func (ee Etcd) Units() []Unit {
-	content := dropinContents(ee.Etcd)
-	if content == "" {
-		return nil
-	}
-	return []Unit{{config.Unit{
-		Name:    "etcd.service",
-		Runtime: true,
-		DropIn:  true,
-		Content: content,
-	}}}
+	return dropinFromConfig(ee.Etcd, "etcd.service")
 }

system/flannel.go

@@ -0,0 +1,17 @@
+package system
+
+import (
+	"github.com/coreos/coreos-cloudinit/config"
+)
+
+// flannel is a top-level structure which embeds its underlying configuration,
+// config.Flannel, and provides the system-specific Unit().
+type Flannel struct {
+	config.Flannel
+}
+
+// Units generates a Unit file drop-in for flannel, if any flannel options were
+// configured in cloud-config
+func (fl Flannel) Units() []Unit {
+	return dropinFromConfig(fl.Flannel, "flannel.service")
+}

system/flannel_test.go

@@ -0,0 +1,40 @@
+package system
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/coreos/coreos-cloudinit/config"
+)
+
+func TestFlannelUnits(t *testing.T) {
+	for _, tt := range []struct {
+		config config.Flannel
+		units  []Unit
+	}{
+		{
+			config.Flannel{},
+			nil,
+		},
+		{
+			config.Flannel{
+				EtcdEndpoint: "http://12.34.56.78:4001",
+				EtcdPrefix:   "/coreos.com/network/tenant1",
+			},
+			[]Unit{{config.Unit{
+				Name: "flannel.service",
+				Content: `[Service]
+Environment="FLANNELD_ETCD_ENDPOINT=http://12.34.56.78:4001"
+Environment="FLANNELD_ETCD_PREFIX=/coreos.com/network/tenant1"
+`,
+				Runtime: true,
+				DropIn:  true,
+			}}},
+		},
+	} {
+		units := Flannel{tt.config}.Units()
+		if !reflect.DeepEqual(units, tt.units) {
+			t.Errorf("bad units (%q): want %v, got %v", tt.config, tt.units, units)
+		}
+	}
+}

system/fleet.go

@@ -29,14 +29,5 @@ type Fleet struct {
 // Units generates a Unit file drop-in for fleet, if any fleet options were
 // configured in cloud-config
 func (fe Fleet) Units() []Unit {
-	content := dropinContents(fe.Fleet)
-	if content == "" {
-		return nil
-	}
-	return []Unit{{config.Unit{
-		Name:    "fleet.service",
-		Runtime: true,
-		DropIn:  true,
-		Content: content,
-	}}}
+	return dropinFromConfig(fe.Fleet, "fleet.service")
 }