Add -wait parameter to debounce watched events

Author: gigablah

README.md

@@ -113,6 +113,8 @@ Options:
       show version
   -watch
       watch for container changes
+  -wait
+      minimum (and/or maximum) duration to wait after each container change before triggering
 
 Arguments:
   template - path to a template to generate
@@ -153,6 +155,9 @@ path to a template to generate
 watch = true
 watch for container changes
 
+wait = "500ms:2s"
+debounce changes with a min:max duration. Only applicable if watch = true
+
 
 [config.NotifyContainers]
 Starts a notify container section
@@ -180,6 +185,7 @@ watch = true
 template = "/etc/docker-gen/templates/nginx.tmpl"
 dest = "/etc/nginx/conf.d/default.conf"
 watch = true
+wait = "500ms:2s"
 
 [config.NotifyContainers]
 nginx = 1  # 1 is a signal number to be sent; here SIGINT

cmd/docker-gen/main.go

@@ -19,6 +19,7 @@ var (
 	buildVersion            string
 	version                 bool
 	watch                   bool
+	wait                    string
 	notifyCmd               string
 	notifyOutput            bool
 	notifySigHUPContainerID string
@@ -85,6 +86,7 @@ func initFlags() {
 	}
 	flag.BoolVar(&version, "version", false, "show version")
 	flag.BoolVar(&watch, "watch", false, "watch for container changes")
+	flag.StringVar(&wait, "wait", "", "minimum and maximum durations to wait (e.g. \"500ms:2s\") before triggering generate")
 	flag.BoolVar(&onlyExposed, "only-exposed", false, "only include containers with exposed ports")
 
 	flag.BoolVar(&onlyPublished, "only-published", false,
@@ -127,10 +129,15 @@ func main() {
 			}
 		}
 	} else {
+		w, err := dockergen.ParseWait(wait)
+		if err != nil {
+			log.Fatalf("error parsing wait interval: %s\n", err)
+		}
 		config := dockergen.Config{
 			Template:         flag.Arg(0),
 			Dest:             flag.Arg(1),
 			Watch:            watch,
+			Wait:             w,
 			NotifyCmd:        notifyCmd,
 			NotifyOutput:     notifyOutput,
 			NotifyContainers: make(map[string]docker.Signal),

config.go

@@ -1,11 +1,18 @@
 package dockergen
 
-import "github.com/fsouza/go-dockerclient"
+import (
+	"errors"
+	"strings"
+	"time"
+
+	"github.com/fsouza/go-dockerclient"
+)
 
 type Config struct {
 	Template         string
 	Dest             string
 	Watch            bool
+	Wait             *Wait
 	NotifyCmd        string
 	NotifyOutput     bool
 	NotifyContainers map[string]docker.Signal
@@ -31,3 +38,47 @@ func (c *ConfigFile) FilterWatches() ConfigFile {
 		Config: configWithWatches,
 	}
 }
+
+type Wait struct {
+	Min time.Duration
+	Max time.Duration
+}
+
+func (w *Wait) UnmarshalText(text []byte) error {
+	wait, err := ParseWait(string(text))
+	if err == nil {
+		w.Min, w.Max = wait.Min, wait.Max
+	}
+	return err
+}
+
+func ParseWait(s string) (*Wait, error) {
+	if len(strings.TrimSpace(s)) < 1 {
+		return &Wait{0, 0}, nil
+	}
+
+	parts := strings.Split(s, ":")
+
+	var (
+		min time.Duration
+		max time.Duration
+		err error
+	)
+	min, err = time.ParseDuration(strings.TrimSpace(parts[0]))
+	if err != nil {
+		return nil, err
+	}
+	if len(parts) > 1 {
+		max, err = time.ParseDuration(strings.TrimSpace(parts[1]))
+		if err != nil {
+			return nil, err
+		}
+		if max < min {
+			return nil, errors.New("Invalid wait interval: max must be larger than min")
+		}
+	} else {
+		max = 4 * min
+	}
+
+	return &Wait{min, max}, nil
+}