Now have some blue/green working. Doesn't play nice with registrator …

…though

configparser.go

@@ -98,6 +98,8 @@ func (f *ConfigParser) parseSettings(lines [][]byte) (projSettings *ProjectConfi
 					projSettings.ProjectName = string(lineParts[2])
 				case "project_sep":
 					projSettings.ProjectSeparator = stripChars(string(lineParts[2]), " \t")
+				case "blue_green":
+					projSettings.BlueGreenMode, _ = strconv.ParseBool(string(lineParts[2]))
 				}
 			}
 			continue

container/container.go

@@ -232,6 +232,38 @@ func (set *Container) launchInForeground(cmd []interface{}, wg *sync.WaitGroup)
 
 }
 
+func (set *Container) BlueGreenDeploy(attach bool, dryRun bool, wg *sync.WaitGroup) error {
+	// rename the current
+	Warning.Println("Temporarily renaming running container")
+	oldName := set.Name + "_old_" + helpers.RandStringBytesMaskImprSrc(5)
+	if err := helpers.RenameContainer(set.Name, oldName); err != nil {
+		return err
+	}
+
+	var oldC = new(Container)
+	*oldC = *set
+	oldC.Name = oldName
+
+	if err := set.Run(attach, dryRun, wg); err != nil {
+		// put back the old
+		set.Stop(nil)
+
+		Warning.Println("Error running new container, reverting container name")
+		if err := helpers.RenameContainer(oldName, set.Name); err != nil {
+			return err
+		}
+		return err
+	}
+
+	// shutdown the old
+	if err := oldC.Stop(nil); err != nil {
+		Error.Println("Error stopping old container")
+		return err
+	}
+
+	return nil
+}
+
 func (set *Container) RecreateAndRun(attach bool, dryRun bool, wg *sync.WaitGroup) error {
 	if !dryRun {
 		set.Rm([]string{"-f"})

helpers/dockerhelper.go

@@ -152,6 +152,13 @@ func GetContainerServiceNameLabel(name string) string {
 	return getLabel(ServiceLabelName, name)
 }
 
+func RenameContainer(currentName string, newName string) error {
+	ses := sh.NewSession()
+	ses.Stderr = ioutil.Discard
+	_, err := ses.Command("docker", "rename", currentName, newName).Output()
+	return err
+}
+
 func getLabel(label string, container string) string {
 	ses := sh.NewSession()
 	ses.Stderr = ioutil.Discard

helpers/stringhelp.go

@@ -1,10 +1,39 @@
 package helpers
 
 import (
+	"math/rand"
 	"strconv"
 	"strings"
+	"time"
 )
 
+var src = rand.NewSource(time.Now().UnixNano())
+
+const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
+const (
+	letterIdxBits = 6                    // 6 bits to represent a letter index
+	letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits
+	letterIdxMax  = 63 / letterIdxBits   // # of letter indices fitting in 63 bits
+)
+
+func RandStringBytesMaskImprSrc(n int) string {
+	b := make([]byte, n)
+	// A src.Int63() generates 63 random bits, enough for letterIdxMax characters!
+	for i, cache, remain := n-1, src.Int63(), letterIdxMax; i >= 0; {
+		if remain == 0 {
+			cache, remain = src.Int63(), letterIdxMax
+		}
+		if idx := int(cache & letterIdxMask); idx < len(letterBytes) {
+			b[i] = letterBytes[idx]
+			i--
+		}
+		cache >>= letterIdxBits
+		remain--
+	}
+
+	return string(b)
+}
+
 func GetNumericSuffix(name string, sep string) (int, error) {
 	namePts := strings.Split(name, sep)
 	instNumStr := namePts[len(namePts)-1]

main.go

@@ -64,12 +64,16 @@ func main() {
 			Aliases: []string{},
 			Usage:   "Create then run or update containers",
 			Action: func(c *cli.Context) {
+				//first get settings
 				settings := getSettings()
+				//then should peek state
+				//TODO
+
 				settings.LaunchSignalWatcher()
 				if err := settings.ContainerCleanupList.CapitanRm([]string{"-f"}, dryRun); err != nil {
 					Warning.Println("Failed to scale down containers:", err)
 				}
-				if err := settings.ContainerList.CapitanUp(attach, dryRun); err != nil {
+				if err := settings.ContainerList.CapitanUp(attach, dryRun, settings.BlueGreenMode); err != nil {
 					Error.Println("Up failed:", err)
 					os.Exit(1)
 				}
@@ -136,7 +140,7 @@ func main() {
 				}
 				if err := settings.ContainerList.Filter(func(i *container.Container) bool {
 					return i.ServiceType == c.Args().Get(0)
-				}).CapitanUp(false, dryRun); err != nil {
+				}).CapitanUp(false, dryRun, settings.BlueGreenMode); err != nil {
 					Error.Println("Scale failed:", err)
 					os.Exit(1)
 				}

projectconfig.go

@@ -42,6 +42,7 @@ var (
 type ProjectConfig struct {
 	ProjectName          string
 	ProjectSeparator     string
+	BlueGreenMode	     bool
 	IsInteractive        bool
 	ContainerList        SettingsList
 	ContainerCleanupList SettingsList
@@ -191,17 +192,21 @@ func (settings SettingsList) CapitanCreate(dryRun bool) error {
 
 		if set.Build != "" {
 			Info.Println("Building image")
-			if err := set.BuildImage(); err != nil {
-				return err
+			if ! dryRun {
+				if err := set.BuildImage(); err != nil {
+					return err
+				}
 			}
 		}
 
 		if helpers.GetImageId(set.Image) == "" {
 			Warning.Printf("Capitan was unable to find image %s locally\n", set.Image)
 
 			Info.Println("Pulling image")
-			if err := helpers.PullImage(set.Image); err != nil {
-				return err
+			if ! dryRun {
+				if err := helpers.PullImage(set.Image); err != nil {
+					return err
+				}
 			}
 		}
 
@@ -220,7 +225,7 @@ func (settings SettingsList) CapitanCreate(dryRun bool) error {
 // Recreates a container if the container's image has a newer id locally
 // OR if the command used to create the container is now changed (i.e.
 // config has changed.
-func (settings SettingsList) CapitanUp(attach bool, dryRun bool) error {
+func (settings SettingsList) CapitanUp(attach bool, dryRun bool, blueGreenMode bool) error {
 	sort.Sort(settings)
 
 	wg := sync.WaitGroup{}
@@ -232,17 +237,22 @@ func (settings SettingsList) CapitanUp(attach bool, dryRun bool) error {
 
 		if set.Build != "" {
 			Info.Println("Building image")
-			if err := set.BuildImage(); err != nil {
-				return err
+			if ! dryRun {
+				if err := set.BuildImage(); err != nil {
+					return err
+				}
 			}
 		}
 
 		if helpers.GetImageId(set.Image) == "" {
 			Warning.Printf("Capitan was unable to find image %s locally\n", set.Image)
 
 			Info.Println("Pulling image")
-			if err := helpers.PullImage(set.Image); err != nil {
-				return err
+
+			if ! dryRun {
+				if err := helpers.PullImage(set.Image); err != nil {
+					return err
+				}
 			}
 		}
 
@@ -267,9 +277,16 @@ func (settings SettingsList) CapitanUp(attach bool, dryRun bool) error {
 
 		if haveArgsChanged(set.Name, set.RunArguments) {
 			// remove and restart
-			Info.Println("Removing (run arguments changed):", set.Name)
-			if err = set.RecreateAndRun(attach, dryRun, &wg); err != nil {
-				return err
+			if blueGreenMode {
+				Info.Println("Run arguments changed, doing blue-green redeploy:", set.Name)
+				if err = set.BlueGreenDeploy(attach, dryRun, &wg); err != nil {
+					return err
+				}
+			} else {
+				Info.Println("Removing (run arguments changed):", set.Name)
+				if err = set.RecreateAndRun(attach, dryRun, &wg); err != nil {
+					return err
+				}
 			}
 			continue
 		}