drop-in: add support for drop-ins

This allows a list of drop-ins for a unit to be declared inline within a
cloud-config. For example:

  #cloud-config
  coreos:
    units:
      - name: docker.service
        drop-ins:
          - name: 50-insecure-registry.conf
            content: |
              [Service]
              Environment=DOCKER_OPTS='--insecure-registry="10.0.1.0/24"'

Documentation/cloud-config.md

@@ -16,7 +16,7 @@ We've designed our implementation to allow the same cloud-config file to work ac
 
 The cloud-config file uses the [YAML][yaml] file format, which uses whitespace and new-lines to delimit lists, associative arrays, and values.
 
-A cloud-config file should contain `#cloud-config`, followed by an associative array which has zero or more of the following keys:
+A cloud-config file must contain `#cloud-config`, followed by an associative array which has zero or more of the following keys:
 
 - `coreos`
 - `ssh_authorized_keys`
@@ -66,7 +66,6 @@ Environment="ETCD_PEER_ADDR=192.0.2.13:7001"
 ```
 
 For more information about the available configuration parameters, see the [etcd documentation][etcd-config].
-Note that hyphens in the coreos.etcd.* keys are mapped to underscores.
 
 _Note: The `$private_ipv4` and `$public_ipv4` substitution variables referenced in other documents are only supported on Amazon EC2, Google Compute Engine, OpenStack, Rackspace, DigitalOcean, and Vagrant._
 
@@ -158,6 +157,10 @@ Each item is an object with the following fields:
 - **content**: Plaintext string representing entire unit file. If no value is provided, the unit is assumed to exist already.
 - **command**: Command to execute on unit: start, stop, reload, restart, try-restart, reload-or-restart, reload-or-try-restart. The default behavior is to not execute any commands.
 - **mask**: Whether to mask the unit file by symlinking it to `/dev/null` (analogous to `systemctl mask <name>`). Note that unlike `systemctl mask`, **this will destructively remove any existing unit file** located at `/etc/systemd/system/<unit>`, to ensure that the mask succeeds. The default value is false.
+- **drop-ins**: A list of unit drop-ins with the following fields:
+  - **name**: String representing unit's name. Required.
+  - **content**: Plaintext string representing entire file. Required.
+
 
 **NOTE:** The command field is ignored for all network, netdev, and link units. The systemd-networkd.service unit will be restarted in their place.
 
@@ -184,6 +187,21 @@ coreos:
         ExecStop=/usr/bin/docker stop -t 2 redis_server
 ```
 
+Add the DOCKER_OPTS environment variable to docker.service.
+
+```yaml
+#cloud-config
+
+coreos:
+  units:
+    - name: docker.service
+      drop-ins:
+        - name: 50-insecure-registry.conf
+          content: |
+            [Service]
+            Environment=DOCKER_OPTS='--insecure-registry="10.0.1.0/24"'
+```
+
 Start the built-in `etcd` and `fleet` services:
 
 ```yaml

config/config_test.go

@@ -335,26 +335,6 @@ func TestCloudConfigSerializationHeader(t *testing.T) {
 	}
 }
 
-// TestDropInIgnored asserts that users are unable to set DropIn=True on units
-func TestDropInIgnored(t *testing.T) {
-	contents := `
-coreos:
-  units:
-    - name: test
-      dropin: true
-`
-	cfg, err := NewCloudConfig(contents)
-	if err != nil || len(cfg.Coreos.Units) != 1 {
-		t.Fatalf("Encountered unexpected error: %v", err)
-	}
-	if len(cfg.Coreos.Units) != 1 || cfg.Coreos.Units[0].Name != "test" {
-		t.Fatalf("Expected 1 unit, but got %d: %v", len(cfg.Coreos.Units), cfg.Coreos.Units)
-	}
-	if cfg.Coreos.Units[0].DropIn {
-		t.Errorf("dropin option on unit in cloud-config was not ignored!")
-	}
-}
-
 func TestCloudConfigUsers(t *testing.T) {
 	contents := `
 users:

config/unit.go

@@ -23,9 +23,10 @@ type Unit struct {
 	Runtime bool         `yaml:"runtime"`
 	Content string       `yaml:"content"`
 	Command string       `yaml:"command" valid:"start,stop,restart,reload,try-restart,reload-or-restart,reload-or-try-restart"`
-
+	DropIns []UnitDropIn `yaml:"drop_ins"`
-	// For drop-in units, a cloudinit.conf is generated.
+}
-	// This is currently unbound in YAML (and hence unsettable in cloud-config files)
+
-	// until the correct behaviour for multiple drop-in units is determined.
+type UnitDropIn struct {
-	DropIn bool `yaml:"-"`
+	Name    string `yaml:"name"`
+	Content string `yaml:"content"`
 }

initialize/config.go

@@ -201,6 +201,11 @@ func processUnits(units []system.Unit, root string, um system.UnitManager) error
 	actions := make([]action, 0, len(units))
 	reload := false
 	for _, unit := range units {
+		if unit.Name == "" {
+			log.Printf("Skipping unit without name")
+			continue
+		}
+
 		if unit.Content != "" {
 			log.Printf("Writing unit %q to filesystem", unit.Name)
 			if err := um.PlaceUnit(unit); err != nil {
@@ -210,6 +215,17 @@ func processUnits(units []system.Unit, root string, um system.UnitManager) error
 			reload = true
 		}
 
+		for _, dropin := range unit.DropIns {
+			if dropin.Name != "" && dropin.Content != "" {
+				log.Printf("Writing drop-in unit %q to filesystem", dropin.Name)
+				if err := um.PlaceUnitDropIn(unit, dropin); err != nil {
+					return err
+				}
+				log.Printf("Wrote drop-in unit %q", dropin.Name)
+				reload = true
+			}
+		}
+
 		if unit.Mask {
 			log.Printf("Masking unit file %q", unit.Name)
 			if err := um.MaskUnit(unit); err != nil {

initialize/config_test.go

@@ -37,6 +37,10 @@ func (tum *TestUnitManager) PlaceUnit(u system.Unit) error {
 	tum.placed = append(tum.placed, u.Name)
 	return nil
 }
+func (tum *TestUnitManager) PlaceUnitDropIn(u system.Unit, d config.UnitDropIn) error {
+	tum.placed = append(tum.placed, u.Name+".d/"+d.Name)
+	return nil
+}
 func (tum *TestUnitManager) EnableUnitFile(u system.Unit) error {
 	tum.enabled = append(tum.enabled, u.Name)
 	return nil
@@ -122,6 +126,69 @@ func TestProcessUnits(t *testing.T) {
 				enabled: []string{"woof"},
 			},
 		},
+		{
+			units: []system.Unit{
+				system.Unit{Unit: config.Unit{
+					Name:    "hi.service",
+					Runtime: true,
+					Content: "[Service]\nExecStart=/bin/echo hi",
+					DropIns: []config.UnitDropIn{
+						{
+							Name:    "lo.conf",
+							Content: "[Service]\nExecStart=/bin/echo lo",
+						},
+						{
+							Name:    "bye.conf",
+							Content: "[Service]\nExecStart=/bin/echo bye",
+						},
+					},
+				}},
+			},
+			result: TestUnitManager{
+				placed:   []string{"hi.service", "hi.service.d/lo.conf", "hi.service.d/bye.conf"},
+				unmasked: []string{"hi.service"},
+				reload:   true,
+			},
+		},
+		{
+			units: []system.Unit{
+				system.Unit{Unit: config.Unit{
+					DropIns: []config.UnitDropIn{
+						{
+							Name:    "lo.conf",
+							Content: "[Service]\nExecStart=/bin/echo lo",
+						},
+					},
+				}},
+			},
+			result: TestUnitManager{},
+		},
+		{
+			units: []system.Unit{
+				system.Unit{Unit: config.Unit{
+					Name: "hi.service",
+					DropIns: []config.UnitDropIn{
+						{
+							Content: "[Service]\nExecStart=/bin/echo lo",
+						},
+					},
+				}},
+			},
+			result: TestUnitManager{},
+		},
+		{
+			units: []system.Unit{
+				system.Unit{Unit: config.Unit{
+					Name: "hi.service",
+					DropIns: []config.UnitDropIn{
+						{
+							Name: "lo.conf",
+						},
+					},
+				}},
+			},
+			result: TestUnitManager{},
+		},
 	}
 
 	for _, tt := range tests {

system/env.go

@@ -25,7 +25,7 @@ import (
 
 // dropinContents generates the contents for a drop-in unit given the config.
 // The argument must be a struct from the 'config' package.
-func dropinContents(e interface{}) string {
+func serviceContents(e interface{}) string {
 	et := reflect.TypeOf(e)
 	ev := reflect.ValueOf(e)
 
@@ -42,16 +42,3 @@ 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/env_test.go

@@ -4,7 +4,7 @@ import (
 	"testing"
 )
 
-func TestDropinContents(t *testing.T) {
+func TestServiceContents(t *testing.T) {
 	tests := []struct {
 		Config   interface{}
 		Contents string
@@ -48,7 +48,7 @@ Environment="D=0.1"
 	}
 
 	for _, tt := range tests {
-		if c := dropinContents(tt.Config); c != tt.Contents {
+		if c := serviceContents(tt.Config); c != tt.Contents {
 			t.Errorf("bad contents (%+v): want %q, got %q", tt, tt.Contents, c)
 		}
 	}

system/etcd.go

@@ -28,5 +28,12 @@ type Etcd struct {
 
 // Units creates a Unit file drop-in for etcd, using any configured options.
 func (ee Etcd) Units() []Unit {
-	return dropinFromConfig(ee.Etcd, "etcd.service")
+	return []Unit{{config.Unit{
+		Name:    "etcd.service",
+		Runtime: true,
+		DropIns: []config.UnitDropIn{{
+			Name:    "20-cloudinit.conf",
+			Content: serviceContents(ee.Etcd),
+		}},
+	}}}
 }

system/etcd_test.go

@@ -30,7 +30,11 @@ func TestEtcdUnits(t *testing.T) {
 	}{
 		{
 			config.Etcd{},
-			nil,
+			[]Unit{{config.Unit{
+				Name:    "etcd.service",
+				Runtime: true,
+				DropIns: []config.UnitDropIn{{Name: "20-cloudinit.conf"}},
+			}}},
 		},
 		{
 			config.Etcd{
@@ -40,11 +44,13 @@ func TestEtcdUnits(t *testing.T) {
 			[]Unit{{config.Unit{
 				Name:    "etcd.service",
 				Runtime: true,
-				DropIn:  true,
+				DropIns: []config.UnitDropIn{{
+					Name: "20-cloudinit.conf",
 					Content: `[Service]
 Environment="ETCD_DISCOVERY=http://disco.example.com/foobar"
 Environment="ETCD_PEER_BIND_ADDR=127.0.0.1:7002"
 `,
+				}},
 			}}},
 		},
 		{
@@ -56,12 +62,14 @@ Environment="ETCD_PEER_BIND_ADDR=127.0.0.1:7002"
 			[]Unit{{config.Unit{
 				Name:    "etcd.service",
 				Runtime: true,
-				DropIn:  true,
+				DropIns: []config.UnitDropIn{{
+					Name: "20-cloudinit.conf",
 					Content: `[Service]
 Environment="ETCD_DISCOVERY=http://disco.example.com/foobar"
 Environment="ETCD_NAME=node001"
 Environment="ETCD_PEER_BIND_ADDR=127.0.0.1:7002"
 `,
+				}},
 			}}},
 		},
 	} {

system/flannel.go

@@ -13,5 +13,12 @@ type Flannel struct {
 // 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, "flanneld.service")
+	return []Unit{{config.Unit{
+		Name:    "flanneld.service",
+		Runtime: true,
+		DropIns: []config.UnitDropIn{{
+			Name:    "20-cloudinit.conf",
+			Content: serviceContents(fl.Flannel),
+		}},
+	}}}
 }

system/flannel_test.go

@@ -14,7 +14,11 @@ func TestFlannelUnits(t *testing.T) {
 	}{
 		{
 			config.Flannel{},
-			nil,
+			[]Unit{{config.Unit{
+				Name:    "flanneld.service",
+				Runtime: true,
+				DropIns: []config.UnitDropIn{{Name: "20-cloudinit.conf"}},
+			}}},
 		},
 		{
 			config.Flannel{
@@ -23,12 +27,14 @@ func TestFlannelUnits(t *testing.T) {
 			},
 			[]Unit{{config.Unit{
 				Name:    "flanneld.service",
+				Runtime: true,
+				DropIns: []config.UnitDropIn{{
+					Name: "20-cloudinit.conf",
 					Content: `[Service]
 Environment="FLANNELD_ETCD_ENDPOINT=http://12.34.56.78:4001"
 Environment="FLANNELD_ETCD_PREFIX=/coreos.com/network/tenant1"
 `,
-				Runtime: true,
+				}},
-				DropIn:  true,
 			}}},
 		},
 	} {

system/fleet.go

@@ -29,5 +29,12 @@ 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 {
-	return dropinFromConfig(fe.Fleet, "fleet.service")
+	return []Unit{{config.Unit{
+		Name:    "fleet.service",
+		Runtime: true,
+		DropIns: []config.UnitDropIn{{
+			Name:    "20-cloudinit.conf",
+			Content: serviceContents(fe.Fleet),
+		}},
+	}}}
 }

system/fleet_test.go

@@ -30,7 +30,11 @@ func TestFleetUnits(t *testing.T) {
 	}{
 		{
 			config.Fleet{},
-			nil,
+			[]Unit{{config.Unit{
+				Name:    "fleet.service",
+				Runtime: true,
+				DropIns: []config.UnitDropIn{{Name: "20-cloudinit.conf"}},
+			}}},
 		},
 		{
 			config.Fleet{
@@ -38,11 +42,13 @@ func TestFleetUnits(t *testing.T) {
 			},
 			[]Unit{{config.Unit{
 				Name:    "fleet.service",
+				Runtime: true,
+				DropIns: []config.UnitDropIn{{
+					Name: "20-cloudinit.conf",
 					Content: `[Service]
 Environment="FLEET_PUBLIC_IP=12.34.56.78"
 `,
-				Runtime: true,
+				}},
-				DropIn:  true,
 			}}},
 		},
 	} {

system/systemd.go

@@ -54,6 +54,19 @@ func (s *systemd) PlaceUnit(u Unit) error {
 	return err
 }
 
+// PlaceUnitDropIn writes a unit drop-in file at its desired destination,
+// creating parent directories as necessary.
+func (s *systemd) PlaceUnitDropIn(u Unit, d config.UnitDropIn) error {
+	file := File{config.File{
+		Path:               u.DropInDestination(s.root, d),
+		Content:            d.Content,
+		RawFilePermissions: "0644",
+	}}
+
+	_, err := WriteFile(&file, "/")
+	return err
+}
+
 func (s *systemd) EnableUnitFile(u Unit) error {
 	conn, err := dbus.New()
 	if err != nil {

system/systemd_test.go

@@ -74,6 +74,64 @@ func TestPlaceUnit(t *testing.T) {
 	}
 }
 
+func TestPlaceUnitDropIn(t *testing.T) {
+	tests := []config.Unit{
+		{
+			Name:    "false.service",
+			Runtime: true,
+			DropIns: []config.UnitDropIn{
+				{
+					Name:    "00-true.conf",
+					Content: "[Service]\nExecStart=\nExecStart=/usr/bin/true\n",
+				},
+			},
+		},
+		{
+			Name: "true.service",
+			DropIns: []config.UnitDropIn{
+				{
+					Name:    "00-false.conf",
+					Content: "[Service]\nExecStart=\nExecStart=/usr/bin/false\n",
+				},
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		dir, err := ioutil.TempDir(os.TempDir(), "coreos-cloudinit-")
+		if err != nil {
+			panic(fmt.Sprintf("Unable to create tempdir: %v", err))
+		}
+
+		u := Unit{tt}
+		sd := &systemd{dir}
+
+		if err := sd.PlaceUnitDropIn(u, u.DropIns[0]); err != nil {
+			t.Fatalf("PlaceUnit(): bad error (%+v): want nil, got %s", tt, err)
+		}
+
+		fi, err := os.Stat(u.DropInDestination(dir, u.DropIns[0]))
+		if err != nil {
+			t.Fatalf("Stat(): bad error (%+v): want nil, got %s", tt, err)
+		}
+
+		if mode := fi.Mode(); mode != os.FileMode(0644) {
+			t.Errorf("bad filemode (%+v): want %v, got %v", tt, os.FileMode(0644), mode)
+		}
+
+		c, err := ioutil.ReadFile(u.DropInDestination(dir, u.DropIns[0]))
+		if err != nil {
+			t.Fatalf("ReadFile(): bad error (%+v): want nil, got %s", tt, err)
+		}
+
+		if string(c) != u.DropIns[0].Content {
+			t.Errorf("bad contents (%+v): want %q, got %q", tt, u.DropIns[0].Content, string(c))
+		}
+
+		os.RemoveAll(dir)
+	}
+}
+
 func TestMachineID(t *testing.T) {
 	dir, err := ioutil.TempDir(os.TempDir(), "coreos-cloudinit-")
 	if err != nil {

system/unit.go

@@ -25,11 +25,9 @@ import (
 	"github.com/coreos/coreos-cloudinit/config"
 )
 
-// Name for drop-in service configuration files created by cloudconfig
-const cloudConfigDropIn = "20-cloudinit.conf"
-
 type UnitManager interface {
 	PlaceUnit(unit Unit) error
+	PlaceUnitDropIn(unit Unit, dropIn config.UnitDropIn) error
 	EnableUnitFile(unit Unit) error
 	RunUnitCommand(unit Unit, command string) (string, error)
 	MaskUnit(unit Unit) error
@@ -66,14 +64,21 @@ func (u Unit) Group() string {
 // argument indicates the effective base directory of the system (similar to a
 // chroot).
 func (u Unit) Destination(root string) string {
+	return path.Join(u.prefix(root), u.Name)
+}
+
+// DropInDestination builds the appropriate absolute file path for the
+// UnitDropIn. The root argument indicates the effective base directory of the
+// system (similar to a chroot) and the dropIn argument is the UnitDropIn for
+// which the destination is being calculated.
+func (u Unit) DropInDestination(root string, dropIn config.UnitDropIn) string {
+	return path.Join(u.prefix(root), fmt.Sprintf("%s.d", u.Name), dropIn.Name)
+}
+
+func (u Unit) prefix(root string) string {
 	dir := "etc"
 	if u.Runtime {
 		dir = "run"
 	}
-
+	return path.Join(root, dir, "systemd", u.Group())
-	if u.DropIn {
-		return path.Join(root, dir, "systemd", u.Group(), fmt.Sprintf("%s.d", u.Name), cloudConfigDropIn)
-	} else {
-		return path.Join(root, dir, "systemd", u.Group(), u.Name)
-	}
 }

system/unit_test.go

@@ -98,3 +98,41 @@ func TestDestination(t *testing.T) {
 		}
 	}
 }
+
+func TestDropInDestination(t *testing.T) {
+	tests := []struct {
+		root       string
+		unitName   string
+		dropInName string
+		runtime    bool
+
+		destination string
+	}{
+		{
+			root:        "/some/dir",
+			unitName:    "foo.service",
+			dropInName:  "bar.conf",
+			destination: "/some/dir/etc/systemd/system/foo.service.d/bar.conf",
+		},
+		{
+			root:        "/some/dir",
+			unitName:    "foo.service",
+			dropInName:  "bar.conf",
+			runtime:     true,
+			destination: "/some/dir/run/systemd/system/foo.service.d/bar.conf",
+		},
+	}
+
+	for _, tt := range tests {
+		u := Unit{config.Unit{
+			Name:    tt.unitName,
+			Runtime: tt.runtime,
+			DropIns: []config.UnitDropIn{{
+				Name: tt.dropInName,
+			}},
+		}}
+		if d := u.DropInDestination(tt.root, u.DropIns[0]); tt.destination != d {
+			t.Errorf("bad destination (%+v): want %q, got %q", tt, tt.destination, d)
+		}
+	}
+}