feat(etcd): Write etcd systemd snippet

Documentation/cloud-config.md

@@ -74,12 +74,38 @@ Provide a list of objects with the following attributes:
 
 ## Custom cloud-config Parameters
 
-### coreos.etcd.discovery_url
+### coreos.etcd
 
-The value of `coreos.etcd.discovery_url` will be used to discover the instance's etcd peers using the [etcd discovery protocol][disco-proto]. Usage of the [public discovery service][disco-service] is encouraged.
+The `coreos.etcd.*` options are translated to a partial systemd unit acting as an etcd configuration file.
+`coreos-cloudinit` will also replace the strings `$private_ipv4` and `$public_ipv4` with the values generated by CoreOS based on a given provider.
 
-[disco-proto]: https://github.com/coreos/etcd/blob/master/Documentation/discovery-protocol.md
-[disco-service]: http://discovery.etcd.io
+For example, the following cloud-config document...
+
+```
+#cloud-config
+
+coreos:
+    etcd:
+        name: node001
+        discovery-url: https://discovery.etcd.io/3445fa65423d8b04df07f59fb40218f8
+        bind-addr: $public_ipv4:4001
+        peer-bind-addr: $private_ipv4:7001
+```
+
+...will generate a systemd snippet like this:
+
+```
+[Service]
+Environment="ETCD_NAME=node001""
+Environment="ETCD_DISCOVERY_URL=https://discovery.etcd.io/3445fa65423d8b04df07f59fb40218f8"
+Environment="ETCD_BIND_ADDR=203.0.113.29:4001"
+Environment="ETCD_PEER_BIND_ADDR=192.0.2.13:7001"
+```
+
+For more information about the available configuration options, see the [etcd documentation][etcd-config].
+Note that hyphens in the coreos.etcd.* keys are mapped to underscores.
+
+[etcd-config]: https://github.com/coreos/etcd/blob/master/Documentation/configuration.md
 
 ### coreos.units
 

cloudinit/cloud_config.go

@@ -12,7 +12,7 @@ const DefaultSSHKeyName = "coreos-cloudinit"
 type CloudConfig struct {
 	SSHAuthorizedKeys []string `yaml:"ssh_authorized_keys"`
 	Coreos            struct {
-		Etcd  struct{ Discovery_URL string }
+		Etcd  EtcdEnvironment
 		Fleet struct{ Autostart bool }
 		Units []Unit
 	}
@@ -98,13 +98,12 @@ func ApplyCloudConfig(cfg CloudConfig, sshKeyName string) error {
 		}
 	}
 
-	if cfg.Coreos.Etcd.Discovery_URL != "" {
-		err := PersistEtcdDiscoveryURL(cfg.Coreos.Etcd.Discovery_URL)
-		if err == nil {
-			log.Printf("Consumed etcd discovery url")
-		} else {
-			log.Fatalf("Failed to persist etcd discovery url to filesystem: %v", err)
+	if len(cfg.Coreos.Etcd) > 0 {
+		if err := WriteEtcdEnvironment("/", cfg.Coreos.Etcd); err != nil {
+			log.Fatalf("Failed to write etcd config to filesystem: %v", err)
 		}
+
+		log.Printf("Wrote etcd config file to filesystem")
 	}
 
 	if len(cfg.Coreos.Units) > 0 {

cloudinit/cloud_config_test.go

@@ -17,10 +17,6 @@ func TestCloudConfigEmpty(t *testing.T) {
 		t.Error("Parsed incorrect number of SSH keys")
 	}
 
-	if cfg.Coreos.Etcd.Discovery_URL != "" {
-		t.Error("Parsed incorrect value of discovery url")
-	}
-
 	if cfg.Coreos.Fleet.Autostart {
 		t.Error("Expected AutostartFleet not to be defined")
 	}
@@ -81,10 +77,6 @@ hostname: trontastic
 		t.Error("Expected first SSH key to be 'foobaz'")
 	}
 
-	if cfg.Coreos.Etcd.Discovery_URL != "https://discovery.etcd.io/827c73219eeb2fa5530027c37bf18877" {
-		t.Error("Failed to parse etcd discovery url")
-	}
-
 	if !cfg.Coreos.Fleet.Autostart {
 		t.Error("Expected AutostartFleet to be true")
 	}

cloudinit/etcd.go

@@ -1,25 +1,48 @@
 package cloudinit
 
 import (
+	"fmt"
 	"io/ioutil"
-	"log"
 	"os"
 	"path"
+	"strings"
 )
 
-const (
-	etcdDiscoveryPath = "/var/run/etcd/bootstrap.disco"
-)
+type EtcdEnvironment map[string]string
 
-func PersistEtcdDiscoveryURL(url string) error {
-	dir := path.Dir(etcdDiscoveryPath)
-	if _, err := os.Stat(dir); err != nil {
-		log.Printf("Creating directory /var/run/etcd")
-		err := os.MkdirAll(dir, os.FileMode(0644))
-		if err != nil {
+func (ec EtcdEnvironment) String() (out string) {
+	public := os.Getenv("COREOS_PUBLIC_IPV4")
+	private := os.Getenv("COREOS_PRIVATE_IPV4")
+
+	out += "[Service]\n"
+
+	for key, val := range ec {
+		key = strings.ToUpper(key)
+		key = strings.Replace(key, "-", "_", -1)
+
+		if public != "" {
+			val = strings.Replace(val, "$public_ipv4", public, -1)
+		}
+
+		if private != "" {
+			val = strings.Replace(val, "$private_ipv4", private, -1)
+		}
+
+		out += fmt.Sprintf("Environment=\"ETCD_%s=%s\"\n", key, val)
+	}
+	return
+}
+
+// Write an EtcdEnvironment to the appropriate path on disk for etcd.service
+func WriteEtcdEnvironment(root string, env EtcdEnvironment) error {
+	cfgDir := path.Join(root, "etc", "systemd", "system", "etcd.service.d")
+	cfgFile := path.Join(cfgDir, "20-cloudinit.conf")
+
+	if _, err := os.Stat(cfgDir); err != nil {
+		if err := os.MkdirAll(cfgDir, os.FileMode(0755)); err != nil {
 			return err
 		}
 	}
 
-	return ioutil.WriteFile(etcdDiscoveryPath, []byte(url), os.FileMode(0644))
+	return ioutil.WriteFile(cfgFile, []byte(env.String()), os.FileMode(0644))
 }

cloudinit/etcd_test.go

@@ -0,0 +1,90 @@
+package cloudinit
+
+import (
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path"
+	"syscall"
+	"testing"
+)
+
+func TestEtcdEnvironment(t *testing.T) {
+	cfg := make(EtcdEnvironment, 0)
+	cfg["discovery_url"] = "http://disco.example.com/foobar"
+	cfg["peer-bind-addr"] = "127.0.0.1:7002"
+
+	env := cfg.String()
+	expect := `[Service]
+Environment="ETCD_DISCOVERY_URL=http://disco.example.com/foobar"
+Environment="ETCD_PEER_BIND_ADDR=127.0.0.1:7002"
+`
+
+	if env != expect {
+		t.Errorf("Generated environment:\n%s\nExpected environment:\n%s", env, expect)
+	}
+}
+
+func TestEtcdEnvironmentReplacement(t *testing.T) {
+	os.Clearenv()
+	os.Setenv("COREOS_PUBLIC_IPV4", "203.0.113.29")
+	os.Setenv("COREOS_PRIVATE_IPV4", "192.0.2.13")
+
+	cfg := make(EtcdEnvironment, 0)
+	cfg["bind-addr"] = "$public_ipv4:4001"
+	cfg["peer-bind-addr"] = "$private_ipv4:7001"
+
+	env := cfg.String()
+	expect := `[Service]
+Environment="ETCD_BIND_ADDR=203.0.113.29:4001"
+Environment="ETCD_PEER_BIND_ADDR=192.0.2.13:7001"
+`
+	if env != expect {
+		t.Errorf("Generated environment:\n%s\nExpected environment:\n%s", env, expect)
+	}
+}
+
+func TestEtcdEnvironmentWrittenToDisk(t *testing.T) {
+	ec := EtcdEnvironment{
+		"discovery_url": "http://disco.example.com/foobar",
+		"peer-bind-addr": "127.0.0.1:7002",
+	}
+	dir, err := ioutil.TempDir(os.TempDir(), "coreos-cloudinit-")
+	if err != nil {
+		t.Fatalf("Unable to create tempdir: %v", err)
+	}
+	defer syscall.Rmdir(dir)
+
+	if err := WriteEtcdEnvironment(dir, ec); err != nil {
+		t.Fatalf("Processing of EtcdEnvironment failed: %v", err)
+	}
+
+	fullPath := path.Join(dir, "etc", "systemd", "system", "etcd.service.d", "20-cloudinit.conf")
+
+	fi, err := os.Stat(fullPath)
+	if err != nil {
+		t.Fatalf("Unable to stat file: %v", err)
+	}
+
+	if fi.Mode() != os.FileMode(0644) {
+		t.Errorf("File has incorrect mode: %v", fi.Mode())
+	}
+
+	contents, err := ioutil.ReadFile(fullPath)
+	if err != nil {
+		t.Fatalf("Unable to read expected file: %v", err)
+	}
+
+	expect := `[Service]
+Environment="ETCD_DISCOVERY_URL=http://disco.example.com/foobar"
+Environment="ETCD_PEER_BIND_ADDR=127.0.0.1:7002"
+`
+	if string(contents) != expect {
+		t.Fatalf("File has incorrect contents")
+	}
+}
+
+func rmdir(path string) error {
+    cmd := exec.Command("rm", "-rf", path)
+    return cmd.Run()
+}