Add notify command option

Runs a command after the template is generated.  Useful for restarting
nginx, haproxy, etc.. Use nginx as an example to add this feature and
ended up also needing to simplify how IP:Port info is accessed.

Author: jwilder

README.md

@@ -1,12 +1,14 @@
 docker-gen
 =====
 
-Config file generator using running docker container meta-data.
+Config file generator using docker container meta-data.
 
-This is mostly a proof of concept to generate config files for:
+This is can be used to generate config files for:
 
  * fluentd, logstash or other centralized logging tools that tail the containers JSON log file.
  * logrotate files to rotate container JSON log files
+ * nginx, haproxy, etc.. reverse proxy configs to route requests to the host to containers
+
 
 [Docker Log Management With Fluentd](http://jasonwilder.com/blog/2014/03/17/docker-log-management-using-fluentd/)
 
@@ -16,9 +18,18 @@ To Run:
 
  `go get github.com/jwilder/docker-gen`
 
- `docker-gen template.file`
+ `docker-gen`
+ `Usage: docker-gen [-watch=false] [-notify="restart xyz"] <template> [<dest>]`
+
+Options:
+* -watch - runs continuously and monitors docker container events.  When containers are started
+or stopped, the template is regenerated.
+* -notify - runs a command after the template is generated.  Useful for restarting nginx, reloading
+haproxy, etc..
+
+If no `<dest>` file is specified, the output is send to stdout.  Mainly useful for debugging.
 
 TODO:
 
- * Add restart command hooks for when files are regenerated.
- * Tail docker event stream to detect when containers are started and stopped automatically
+ * Add a way to filter out containers in templates
+

docker-gen.go

@@ -10,25 +10,41 @@ import (
 	"net/http"
 	"net/http/httputil"
 	"os"
+	"os/exec"
 	"os/signal"
 	"path/filepath"
+	"strings"
 	"syscall"
 	"text/template"
 )
 
-var watch bool
+var (
+	watch     bool
+	notifyCmd string
+)
 
 type Event struct {
 	ContainerId string `json:"id"`
 	Status      string `json:"status"`
 	Image       string `json:"from"`
 }
 
+type Address struct {
+	IP   string
+	Port string
+}
+type RuntimeContainer struct {
+	ID        string
+	Addresses []Address
+	Image     string
+}
+
 func usage() {
-	println("Usage: docker-gen [-watch] <template> [<dest>]")
+	println("Usage: docker-gen [-watch=false] [-notify=\"restart xyz\"] <template> [<dest>]")
 }
 
-func generateFile(templatePath string, containers []docker.APIContainers) {
+func generateFile(templatePath string, containers []*RuntimeContainer) {
+
 	tmpl, err := template.ParseFiles(templatePath)
 	if err != nil {
 		panic(err)
@@ -44,6 +60,9 @@ func generateFile(templatePath string, containers []docker.APIContainers) {
 	}
 
 	err = tmpl.ExecuteTemplate(dest, filepath.Base(templatePath), containers)
+	if err != nil {
+		fmt.Printf("template error: %s\n", err)
+	}
 }
 
 func newConn() (*httputil.ClientConn, error) {
@@ -110,20 +129,59 @@ func getEvents() chan *Event {
 }
 
 func generateFromContainers(client *docker.Client) {
-	containers, err := client.ListContainers(docker.ListContainersOptions{
+	apiContainers, err := client.ListContainers(docker.ListContainersOptions{
 		All: false,
 	})
 	if err != nil {
 		fmt.Printf("error listing containers: %s", err)
 		return
 	}
 
+	containers := []*RuntimeContainer{}
+	for _, apiContainer := range apiContainers {
+		container, err := client.InspectContainer(apiContainer.ID)
+		if err != nil {
+			fmt.Printf("error inspecting container: %s: %s", apiContainer.ID, err)
+			continue
+		}
+
+		runtimeContainer := &RuntimeContainer{
+			ID:        container.ID,
+			Image:     container.Config.Image,
+			Addresses: []Address{},
+		}
+		for k, _ := range container.NetworkSettings.Ports {
+			runtimeContainer.Addresses = append(runtimeContainer.Addresses,
+				Address{
+					IP:   container.NetworkSettings.IPAddress,
+					Port: k.Port(),
+				})
+		}
+		containers = append(containers, runtimeContainer)
+	}
+
 	generateFile(flag.Arg(0), containers)
 }
 
+func runNotifyCmd() {
+	if notifyCmd == "" {
+		return
+	}
+
+	args := strings.Split(notifyCmd, " ")
+	cmd := exec.Command(args[0], args[1:]...)
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		fmt.Printf("error running notify command: %s\n", err)
+	}
+	print(string(output))
+
+}
+
 func main() {
 
 	flag.BoolVar(&watch, "watch", false, "watch for container changes")
+	flag.StringVar(&notifyCmd, "notify", "", "run command after template is regenerated")
 	flag.Parse()
 
 	if flag.NArg() < 1 {
@@ -139,6 +197,7 @@ func main() {
 	}
 
 	generateFromContainers(client)
+	runNotifyCmd()
 	if !watch {
 		return
 	}
@@ -148,6 +207,7 @@ func main() {
 		event := <-eventChan
 		if event.Status == "start" || event.Status == "stop" {
 			generateFromContainers(client)
+			runNotifyCmd()
 		}
 	}
 

templates/nginx.tmpl

@@ -0,0 +1,21 @@
+upstream docker {
+{{range $key, $value := .}}
+	{}
+	{{with $address := index $value.Addresses 0 }}
+	server {{ $address.IP}}:{{ $address.Port}};
+	{{end}}
+{{end}}
+}
+
+server {
+	root /usr/share/nginx/www;
+	index index.html index.htm;
+
+	server_name localhost;
+
+	location / {
+	    proxy_pass http://docker;
+	    include /etc/nginx/proxy_params;
+	}
+}
+