Merge pull request #104 from webner/skip-blank-lines

skip-blank-lines option

Author: jwilder

README.md

@@ -77,7 +77,7 @@ $ docker run -d --name nginx-gen --volumes-from nginx \
 ### Usage
 ```
 $ docker-gen
-Usage: docker-gen [-config file] [-watch=false] [-notify="restart xyz"] [-notify-sighup="nginx-proxy"] [-interval=0] [-endpoint tcp|unix://..] [-tlsverify] [-tlscert file] [-tlskey file] [-tlscacert file] <template> [<dest>]
+Usage: docker-gen [-config file] [-watch=false] [-notify="restart xyz"] [-notify-sighup="nginx-proxy"] [-interval=0] [-endpoint tcp|unix://..] [-tlsverify] [-tlscert file] [-tlskey file] [-tlscacert file] [-keep-blank-lines] <template> [<dest>]
 ```
 
 *Options:*
@@ -92,6 +92,7 @@ Usage: docker-gen [-config file] [-watch=false] [-notify="restart xyz"] [-notify
   -notify-sighup="": send HUP signal to container.  Equivalent to `docker kill -s HUP container-ID`
   -only-exposed=false: only include containers with exposed ports
   -only-published=false: only include containers with published ports (implies -only-exposed)
+  -keep-blank-lines=false: keep blank lines in the output file
   -tlscacert="": path to TLS CA certificate file
   -tlscert="": path to TLS client certificate file
   -tlskey="": path to TLS client key file

docker-gen.go

@@ -29,6 +29,7 @@ var (
 	configFiles             stringslice
 	configs                 ConfigFile
 	interval                int
+	keepBlankLines          bool
 	endpoint                string
 	tlsCert                 string
 	tlsKey                  string
@@ -114,6 +115,7 @@ type Config struct {
 	OnlyExposed      bool
 	OnlyPublished    bool
 	Interval         int
+	KeepBlankLines   bool
 }
 
 type ConfigFile struct {
@@ -391,6 +393,7 @@ func initFlags() {
 		"send HUP signal to container.  Equivalent to `docker kill -s HUP container-ID`")
 	flag.Var(&configFiles, "config", "config files with template directives. Config files will be merged if this option is specified multiple times.")
 	flag.IntVar(&interval, "interval", 0, "notify command interval (secs)")
+	flag.BoolVar(&keepBlankLines, "keep-blank-lines", false, "keep blank lines in the output file")
 	flag.StringVar(&endpoint, "endpoint", "", "docker api endpoint (tcp|unix://..). Default unix:///var/run/docker.sock")
 	flag.StringVar(&tlsCert, "tlscert", filepath.Join(certPath, "cert.pem"), "path to TLS client certificate file")
 	flag.StringVar(&tlsKey, "tlskey", filepath.Join(certPath, "key.pem"), "path to TLS client key file")
@@ -431,6 +434,7 @@ func main() {
 			OnlyExposed:      onlyExposed,
 			OnlyPublished:    onlyPublished,
 			Interval:         interval,
+			KeepBlankLines:   keepBlankLines,
 		}
 		if notifySigHUPContainerID != "" {
 			config.NotifyContainers[notifySigHUPContainerID] = docker.SIGHUP

template.go

@@ -362,12 +362,6 @@ func newTemplate(name string) *template.Template {
 }
 
 func generateFile(config Config, containers Context) bool {
-	templatePath := config.Template
-	tmpl, err := newTemplate(filepath.Base(templatePath)).ParseFiles(templatePath)
-	if err != nil {
-		log.Fatalf("unable to parse template: %s", err)
-	}
-
 	filteredContainers := Context{}
 	if config.OnlyPublished {
 		for _, container := range containers {
@@ -385,42 +379,41 @@ func generateFile(config Config, containers Context) bool {
 		filteredContainers = containers
 	}
 
-	dest := os.Stdout
+	contents := executeTemplate(config.Template, filteredContainers)
+
+	if !config.KeepBlankLines {
+		buf := new(bytes.Buffer)
+		removeBlankLines(bytes.NewReader(contents), buf)
+		contents = buf.Bytes()
+	}
+
 	if config.Dest != "" {
-		dest, err = ioutil.TempFile(filepath.Dir(config.Dest), "docker-gen")
+		dest, err := ioutil.TempFile(filepath.Dir(config.Dest), "docker-gen")
 		defer func() {
 			dest.Close()
 			os.Remove(dest.Name())
 		}()
 		if err != nil {
 			log.Fatalf("unable to create temp file: %s\n", err)
 		}
-	}
-
-	var buf bytes.Buffer
-	multiwriter := io.MultiWriter(dest, &buf)
-	err = tmpl.ExecuteTemplate(multiwriter, filepath.Base(templatePath), &filteredContainers)
-	if err != nil {
-		log.Fatalf("template error: %s\n", err)
-	}
 
-	if config.Dest != "" {
+		dest.Write(contents)
 
-		contents := []byte{}
+		oldContents := []byte{}
 		if fi, err := os.Stat(config.Dest); err == nil {
 			if err := dest.Chmod(fi.Mode()); err != nil {
 				log.Fatalf("unable to chmod temp file: %s\n", err)
 			}
 			if err := dest.Chown(int(fi.Sys().(*syscall.Stat_t).Uid), int(fi.Sys().(*syscall.Stat_t).Gid)); err != nil {
 				log.Fatalf("unable to chown temp file: %s\n", err)
 			}
-			contents, err = ioutil.ReadFile(config.Dest)
+			oldContents, err = ioutil.ReadFile(config.Dest)
 			if err != nil {
 				log.Fatalf("unable to compare current file contents: %s: %s\n", config.Dest, err)
 			}
 		}
 
-		if bytes.Compare(contents, buf.Bytes()) != 0 {
+		if bytes.Compare(oldContents, contents) != 0 {
 			err = os.Rename(dest.Name(), config.Dest)
 			if err != nil {
 				log.Fatalf("unable to create dest file %s: %s\n", config.Dest, err)
@@ -429,6 +422,22 @@ func generateFile(config Config, containers Context) bool {
 			return true
 		}
 		return false
+	} else {
+		os.Stdout.Write(contents)
 	}
 	return true
 }
+
+func executeTemplate(templatePath string, containers Context) []byte {
+	tmpl, err := newTemplate(filepath.Base(templatePath)).ParseFiles(templatePath)
+	if err != nil {
+		log.Fatalf("unable to parse template: %s", err)
+	}
+
+	buf := new(bytes.Buffer)
+	err = tmpl.ExecuteTemplate(buf, filepath.Base(templatePath), &containers)
+	if err != nil {
+		log.Fatalf("template error: %s\n", err)
+	}
+	return buf.Bytes()
+}

utils.go

@@ -1,8 +1,11 @@
 package main
 
 import (
+	"bufio"
+	"io"
 	"os"
 	"strings"
+	"unicode"
 )
 
 func getEndpoint() (string, error) {
@@ -50,3 +53,31 @@ func pathExists(path string) (bool, error) {
 	}
 	return false, err
 }
+
+func isBlank(str string) bool {
+	for _, r := range str {
+		if !unicode.IsSpace(r) {
+			return false
+		}
+	}
+	return true
+}
+
+func removeBlankLines(reader io.Reader, writer io.Writer) {
+	breader := bufio.NewReader(reader)
+	bwriter := bufio.NewWriter(writer)
+
+	for {
+		line, err := breader.ReadString('\n')
+
+		if !isBlank(line) {
+			bwriter.WriteString(line)
+		}
+
+		if err != nil {
+			break
+		}
+	}
+
+	bwriter.Flush()
+}

utils_test.go

@@ -1,8 +1,10 @@
 package main
 
 import (
+	"bytes"
 	"flag"
 	"os"
+	"strings"
 	"testing"
 )
 
@@ -87,3 +89,58 @@ func TestSplitKeyValueSlice(t *testing.T) {
 
 	}
 }
+
+func TestIsBlank(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected bool
+	}{
+		{"", true},
+		{" ", true},
+		{"   ", true},
+		{"\t", true},
+		{"\t\n\v\f\r\u0085\u00A0", true},
+		{"a", false},
+		{" a ", false},
+		{"a ", false},
+		{" a", false},
+		{"日本語", false},
+	}
+
+	for _, i := range tests {
+		v := isBlank(i.input)
+		if v != i.expected {
+			t.Fatalf("expected '%v'. got '%v'", i.expected, v)
+		}
+	}
+}
+
+func TestRemoveBlankLines(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected string
+	}{
+		{"", ""},
+		{"\r\n\r\n", ""},
+		{"line1\nline2", "line1\nline2"},
+		{"line1\n\nline2", "line1\nline2"},
+		{"\n\n\n\nline1\n\nline2", "line1\nline2"},
+		{"\n\n\n\n\n  \n \n \n", ""},
+
+		// windows line endings \r\n
+		{"line1\r\nline2", "line1\r\nline2"},
+		{"line1\r\n\r\nline2", "line1\r\nline2"},
+
+		// keep last new line
+		{"line1\n", "line1\n"},
+		{"line1\r\n", "line1\r\n"},
+	}
+
+	for _, i := range tests {
+		output := new(bytes.Buffer)
+		removeBlankLines(strings.NewReader(i.input), output)
+		if output.String() != i.expected {
+			t.Fatalf("expected '%v'. got '%v'", i.expected, output)
+		}
+	}
+}