Merge pull request #164 from crawford/datasources

datasources: Add support for specifying multiple datasources

coreos-cloudinit.go

@@ -4,13 +4,21 @@ import (
 	"flag"
 	"fmt"
 	"os"
+	"sync"
+	"time"
 
 	"github.com/coreos/coreos-cloudinit/datasource"
 	"github.com/coreos/coreos-cloudinit/initialize"
+	"github.com/coreos/coreos-cloudinit/pkg"
 	"github.com/coreos/coreos-cloudinit/system"
 )
 
-const version = "0.7.7+git"
+const (
+	version               = "0.7.7+git"
+	datasourceInterval    = 100 * time.Millisecond
+	datasourceMaxInterval = 30 * time.Second
+	datasourceTimeout     = 5 * time.Minute
+)
 
 var (
 	printVersion  bool
@@ -68,12 +76,18 @@ func main() {
 		os.Exit(1)
 	}
 
-	ds := getDatasource()
-	if ds == nil {
-		fmt.Println("Provide exactly one of --from-file, --from-configdrive, --from-metadata-service, --from-url or --from-proc-cmdline")
+	dss := getDatasources()
+	if len(dss) == 0 {
+		fmt.Println("Provide at least one of --from-file, --from-configdrive, --from-metadata-service, --from-url or --from-proc-cmdline")
 		os.Exit(1)
 	}
 
+	ds := selectDatasource(dss)
+	if ds == nil {
+		fmt.Println("No datasources available in time")
+		die()
+	}
+
 	fmt.Printf("Fetching user-data from datasource of type %q\n", ds.Type())
 	userdataBytes, err := ds.FetchUserdata()
 	if err != nil {
@@ -119,33 +133,70 @@ func main() {
 	}
 }
 
-func getDatasource() datasource.Datasource {
-	var ds datasource.Datasource
-	var n int
+func getDatasources() []datasource.Datasource {
+	dss := make([]datasource.Datasource, 0, 5)
 	if sources.file != "" {
-		ds = datasource.NewLocalFile(sources.file)
-		n++
+		dss = append(dss, datasource.NewLocalFile(sources.file))
 	}
 	if sources.url != "" {
-		ds = datasource.NewRemoteFile(sources.url)
-		n++
+		dss = append(dss, datasource.NewRemoteFile(sources.url))
 	}
 	if sources.configDrive != "" {
-		ds = datasource.NewConfigDrive(sources.configDrive)
-		n++
+		dss = append(dss, datasource.NewConfigDrive(sources.configDrive))
 	}
 	if sources.metadataService {
-		ds = datasource.NewMetadataService()
-		n++
+		dss = append(dss, datasource.NewMetadataService())
 	}
 	if sources.procCmdLine {
-		ds = datasource.NewProcCmdline()
-		n++
+		dss = append(dss, datasource.NewProcCmdline())
 	}
-	if n != 1 {
-		return nil
+	return dss
+}
+
+func selectDatasource(sources []datasource.Datasource) datasource.Datasource {
+	ds := make(chan datasource.Datasource)
+	stop := make(chan struct{})
+	var wg sync.WaitGroup
+
+	for _, s := range sources {
+		wg.Add(1)
+		go func(s datasource.Datasource) {
+			defer wg.Done()
+
+			duration := datasourceInterval
+			for {
+				fmt.Printf("Checking availability of %q\n", s.Type())
+				if s.IsAvailable() {
+					ds <- s
+					return
+				} else if !s.AvailabilityChanges() {
+					return
+				}
+				select {
+				case <-stop:
+					return
+				case <-time.Tick(duration):
+					duration = pkg.ExpBackoff(duration, datasourceMaxInterval)
+				}
+			}
+		}(s)
 	}
-	return ds
+
+	done := make(chan struct{})
+	go func() {
+		wg.Wait()
+		close(done)
+	}()
+
+	var s datasource.Datasource
+	select {
+	case s = <-ds:
+	case <-done:
+	case <-time.Tick(datasourceTimeout):
+	}
+
+	close(stop)
+	return s
 }
 
 func processUserdata(userdata string, env *initialize.Environment) error {

datasource/configdrive.go

@@ -14,6 +14,15 @@ func NewConfigDrive(root string) *configDrive {
 	return &configDrive{path.Join(root, "openstack")}
 }
 
+func (cd *configDrive) IsAvailable() bool {
+	_, err := os.Stat(cd.root)
+	return !os.IsNotExist(err)
+}
+
+func (cd *configDrive) AvailabilityChanges() bool {
+	return true
+}
+
 func (cd *configDrive) ConfigRoot() string {
 	return cd.root
 }

datasource/datasource.go

@@ -1,6 +1,8 @@
 package datasource
 
 type Datasource interface {
+	IsAvailable() bool
+	AvailabilityChanges() bool
 	ConfigRoot() string
 	FetchMetadata() ([]byte, error)
 	FetchUserdata() ([]byte, error)

datasource/file.go

@@ -2,6 +2,7 @@ package datasource
 
 import (
 	"io/ioutil"
+	"os"
 )
 
 type localFile struct {
@@ -12,6 +13,15 @@ func NewLocalFile(path string) *localFile {
 	return &localFile{path}
 }
 
+func (f *localFile) IsAvailable() bool {
+	_, err := os.Stat(f.path)
+	return !os.IsNotExist(err)
+}
+
+func (f *localFile) AvailabilityChanges() bool {
+	return true
+}
+
 func (f *localFile) ConfigRoot() string {
 	return ""
 }

datasource/metadata_service.go

@@ -32,13 +32,23 @@ const (
 type metadataService struct{}
 
 type getter interface {
-	Get(string) ([]byte, error)
+	GetRetry(string) ([]byte, error)
 }
 
 func NewMetadataService() *metadataService {
 	return &metadataService{}
 }
 
+func (ms *metadataService) IsAvailable() bool {
+	client := pkg.NewHttpClient()
+	_, err := client.Get(BaseUrl)
+	return (err == nil)
+}
+
+func (ms *metadataService) AvailabilityChanges() bool {
+	return true
+}
+
 func (ms *metadataService) ConfigRoot() string {
 	return ""
 }
@@ -49,12 +59,12 @@ func (ms *metadataService) FetchMetadata() ([]byte, error) {
 
 func (ms *metadataService) FetchUserdata() ([]byte, error) {
 	client := pkg.NewHttpClient()
-	if data, err := client.Get(Ec2UserdataUrl); err == nil {
+	if data, err := client.GetRetry(Ec2UserdataUrl); err == nil {
 		return data, err
 	} else if _, ok := err.(pkg.ErrTimeout); ok {
 		return data, err
 	}
-	return client.Get(OpenstackUserdataUrl)
+	return client.GetRetry(OpenstackUserdataUrl)
 }
 
 func (ms *metadataService) Type() string {
@@ -62,7 +72,7 @@ func (ms *metadataService) Type() string {
 }
 
 func fetchMetadata(client getter) ([]byte, error) {
-	if metadata, err := client.Get(OpenstackMetadataUrl); err == nil {
+	if metadata, err := client.GetRetry(OpenstackMetadataUrl); err == nil {
 		return metadata, nil
 	} else if _, ok := err.(pkg.ErrTimeout); ok {
 		return nil, err
@@ -76,7 +86,7 @@ func fetchMetadata(client getter) ([]byte, error) {
 }
 
 func fetchAttributes(client getter, url string) ([]string, error) {
-	resp, err := client.Get(url)
+	resp, err := client.GetRetry(url)
 	if err != nil {
 		return nil, err
 	}

datasource/metadata_service_test.go

@@ -14,7 +14,7 @@ type TestHttpClient struct {
 	err      error
 }
 
-func (t *TestHttpClient) Get(url string) ([]byte, error) {
+func (t *TestHttpClient) GetRetry(url string) ([]byte, error) {
 	if t.err != nil {
 		return nil, t.err
 	}

datasource/proc_cmdline.go

@@ -22,6 +22,21 @@ func NewProcCmdline() *procCmdline {
 	return &procCmdline{Location: ProcCmdlineLocation}
 }
 
+func (c *procCmdline) IsAvailable() bool {
+	contents, err := ioutil.ReadFile(c.Location)
+	if err != nil {
+		return false
+	}
+
+	cmdline := strings.TrimSpace(string(contents))
+	_, err = findCloudConfigURL(cmdline)
+	return (err == nil)
+}
+
+func (c *procCmdline) AvailabilityChanges() bool {
+	return false
+}
+
 func (c *procCmdline) ConfigRoot() string {
 	return ""
 }
@@ -43,7 +58,7 @@ func (c *procCmdline) FetchUserdata() ([]byte, error) {
 	}
 
 	client := pkg.NewHttpClient()
-	cfg, err := client.Get(url)
+	cfg, err := client.GetRetry(url)
 	if err != nil {
 		return nil, err
 	}

datasource/url.go

@@ -10,6 +10,16 @@ func NewRemoteFile(url string) *remoteFile {
 	return &remoteFile{url}
 }
 
+func (f *remoteFile) IsAvailable() bool {
+	client := pkg.NewHttpClient()
+	_, err := client.Get(f.url)
+	return (err == nil)
+}
+
+func (f *remoteFile) AvailabilityChanges() bool {
+	return true
+}
+
 func (f *remoteFile) ConfigRoot() string {
 	return ""
 }
@@ -20,7 +30,7 @@ func (f *remoteFile) FetchMetadata() ([]byte, error) {
 
 func (f *remoteFile) FetchUserdata() ([]byte, error) {
 	client := pkg.NewHttpClient()
-	return client.Get(f.url)
+	return client.GetRetry(f.url)
 }
 
 func (f *remoteFile) Type() string {

initialize/ssh_keys.go

@@ -25,7 +25,7 @@ func SSHImportKeysFromURL(system_user string, url string) error {
 
 func fetchUserKeys(url string) ([]string, error) {
 	client := pkg.NewHttpClient()
-	data, err := client.Get(url)
+	data, err := client.GetRetry(url)
 	if err != nil {
 		return nil, err
 	}

pkg/http_client.go

@@ -20,15 +20,23 @@ const (
 
 type Err error
 
-type ErrTimeout struct{
+type ErrTimeout struct {
 	Err
 }
 
-type ErrNotFound struct{
+type ErrNotFound struct {
 	Err
 }
 
-type ErrInvalid struct{
+type ErrInvalid struct {
+	Err
+}
+
+type ErrServer struct {
+	Err
+}
+
+type ErrNetwork struct {
 	Err
 }
 
@@ -45,18 +53,42 @@ type HttpClient struct {
 
 	// Whether or not to skip TLS verification. Defaults to false
 	SkipTLS bool
+
+	client *http.Client
 }
 
 func NewHttpClient() *HttpClient {
-	return &HttpClient{
+	hc := &HttpClient{
 		MaxBackoff: time.Second * 5,
 		MaxRetries: 15,
 		Timeout:    time.Duration(2) * time.Second,
 		SkipTLS:    false,
 	}
+
+	// We need to create our own client in order to add timeout support.
+	// TODO(c4milo) Replace it once Go 1.3 is officially used by CoreOS
+	// More info: https://code.google.com/p/go/source/detail?r=ada6f2d5f99f
+	hc.client = &http.Client{
+		Transport: &http.Transport{
+			TLSClientConfig: &tls.Config{
+				InsecureSkipVerify: hc.SkipTLS,
+			},
+			Dial: func(network, addr string) (net.Conn, error) {
+				deadline := time.Now().Add(hc.Timeout)
+				c, err := net.DialTimeout(network, addr, hc.Timeout)
+				if err != nil {
+					return nil, err
+				}
+				c.SetDeadline(deadline)
+				return c, nil
+			},
+		},
+	}
+
+	return hc
 }
 
-func expBackoff(interval, max time.Duration) time.Duration {
+func ExpBackoff(interval, max time.Duration) time.Duration {
 	interval = interval * 2
 	if interval > max {
 		interval = max
@@ -64,8 +96,8 @@ func expBackoff(interval, max time.Duration) time.Duration {
 	return interval
 }
 
-// Fetches a given URL with support for exponential backoff and maximum retries
-func (h *HttpClient) Get(rawurl string) ([]byte, error) {
+// GetRetry fetches a given URL with support for exponential backoff and maximum retries
+func (h *HttpClient) GetRetry(rawurl string) ([]byte, error) {
 	if rawurl == "" {
 		return nil, ErrInvalid{errors.New("URL is empty. Skipping.")}
 	}
@@ -83,55 +115,42 @@ func (h *HttpClient) Get(rawurl string) ([]byte, error) {
 
 	dataURL := url.String()
 
-	// We need to create our own client in order to add timeout support.
-	// TODO(c4milo) Replace it once Go 1.3 is officially used by CoreOS
-	// More info: https://code.google.com/p/go/source/detail?r=ada6f2d5f99f
-	transport := &http.Transport{
-		TLSClientConfig: &tls.Config{
-			InsecureSkipVerify: h.SkipTLS,
-		},
-		Dial: func(network, addr string) (net.Conn, error) {
-			deadline := time.Now().Add(h.Timeout)
-			c, err := net.DialTimeout(network, addr, h.Timeout)
-			if err != nil {
-				return nil, err
-			}
-			c.SetDeadline(deadline)
-			return c, nil
-		},
-	}
-
-	client := &http.Client{
-		Transport: transport,
-	}
-
 	duration := 50 * time.Millisecond
 	for retry := 1; retry <= h.MaxRetries; retry++ {
 		log.Printf("Fetching data from %s. Attempt #%d", dataURL, retry)
 
-		resp, err := client.Get(dataURL)
-
-		if err == nil {
-			defer resp.Body.Close()
-			status := resp.StatusCode / 100
-
-			if status == HTTP_2xx {
-				return ioutil.ReadAll(resp.Body)
-			}
-
-			if status == HTTP_4xx {
-				return nil, ErrNotFound{fmt.Errorf("Not found. HTTP status code: %d", resp.StatusCode)}
-			}
-
-			log.Printf("Server error. HTTP status code: %d", resp.StatusCode)
-		} else {
-			log.Printf("Unable to fetch data: %s", err.Error())
+		data, err := h.Get(dataURL)
+		switch err.(type) {
+		case ErrNetwork:
+			log.Printf(err.Error())
+		case ErrServer:
+			log.Printf(err.Error())
+		case ErrNotFound:
+			return data, err
+		default:
+			return data, err
 		}
 
-		duration = expBackoff(duration, h.MaxBackoff)
+		duration = ExpBackoff(duration, h.MaxBackoff)
 		log.Printf("Sleeping for %v...", duration)
 		time.Sleep(duration)
 	}
 
 	return nil, ErrTimeout{fmt.Errorf("Unable to fetch data. Maximum retries reached: %d", h.MaxRetries)}
 }
+
+func (h *HttpClient) Get(dataURL string) ([]byte, error) {
+	if resp, err := h.client.Get(dataURL); err == nil {
+		defer resp.Body.Close()
+		switch resp.StatusCode / 100 {
+		case HTTP_2xx:
+			return ioutil.ReadAll(resp.Body)
+		case HTTP_4xx:
+			return nil, ErrNotFound{fmt.Errorf("Not found. HTTP status code: %d", resp.StatusCode)}
+		default:
+			return nil, ErrServer{fmt.Errorf("Server error. HTTP status code: %d", resp.StatusCode)}
+		}
+	} else {
+		return nil, ErrNetwork{fmt.Errorf("Unable to fetch data: %s", err.Error())}
+	}
+}

pkg/http_client_test.go

@@ -14,7 +14,7 @@ func TestExpBackoff(t *testing.T) {
 	duration := time.Millisecond
 	max := time.Hour
 	for i := 0; i < math.MaxUint16; i++ {
-		duration = expBackoff(duration, max)
+		duration = ExpBackoff(duration, max)
 		if duration < 0 {
 			t.Fatalf("duration too small: %v %v", duration, i)
 		}
@@ -51,7 +51,7 @@ func TestGetURLExpBackOff(t *testing.T) {
 		ts := httptest.NewServer(mux)
 		defer ts.Close()
 
-		data, err := client.Get(ts.URL)
+		data, err := client.GetRetry(ts.URL)
 		if err != nil {
 			t.Errorf("Test case %d produced error: %v", i, err)
 		}
@@ -76,7 +76,7 @@ func TestGetURL4xx(t *testing.T) {
 	}))
 	defer ts.Close()
 
-	_, err := client.Get(ts.URL)
+	_, err := client.GetRetry(ts.URL)
 	if err == nil {
 		t.Errorf("Incorrect result\ngot:  %s\nwant: %s", err.Error(), "Not found. HTTP status code: 404")
 	}
@@ -107,7 +107,7 @@ coreos:
 	}))
 	defer ts.Close()
 
-	data, err := client.Get(ts.URL)
+	data, err := client.GetRetry(ts.URL)
 	if err != nil {
 		t.Errorf("Incorrect result\ngot:  %v\nwant: %v", err, nil)
 	}
@@ -132,7 +132,7 @@ func TestGetMalformedURL(t *testing.T) {
 	}
 
 	for _, test := range tests {
-		_, err := client.Get(test.url)
+		_, err := client.GetRetry(test.url)
 		if err == nil || err.Error() != test.want {
 			t.Errorf("Incorrect result\ngot:  %v\nwant: %v", err, test.want)
 		}