Add new -overlay option to overlay files prior to templatizing

    - overlays files onto the container at run-time, allowing for entire directory trees of files
      to be dropped into a container based on ENV settings

      `dockerize -overlay "/tmp/overlays/_common/html:/usr/share/nginx/" \
                 -overlay "/tmp/overlays/{{ .Env.DEPLOYMENT_ENV }}/html:/usr/share/nginx/" ...`

Small improvements:
    - rename Context to EnvContext and move it into template.go, which is the
      only place it is used.
    - Add early exit to waitForDependencies() if waitFlag is nil
    - string_template_eval utility function added
    - apply string_template_eval to -template args so users use ENV vars to select the desired template
      at run-time like this:
        `dockerize -template '/etc/nginx/sites-available/{{ .Env FLAVOR }}.default.tmpl:/etc/nginx/sites-available/default'

Nginx Example improvements
    - FROM nginx:1.9 is MUCH faster than compiling your own nginx
    - Add a Makefile for examples/nginx
    - Install the locally built image of "dockerize" into nginx, this greatly simplifies testing

Author: markriggins

README.md

@@ -53,10 +53,10 @@ CMD dockerize -template /etc/nginx/nginx.tmpl:/etc/nginx/nginx.conf -stdout /var
 
 ### Command-line Options
 
-You can specify multiple templates by passing using `-template` multiple times:
+You can specify multiple templates by passing `-template` multiple times:
 
 ```
-$ dockerize -template template1.tmpl:file1.cfg -template template2.tmpl:file3
+$ dockerize -template template1.tmpl:file1.cfg -template template2.tmpl:file2
 
 ```
 
@@ -68,6 +68,15 @@ $ dockerize -template template1.tmpl
 ```
 
 
+You can overlay files onto the container at runtime by passing `-overlay` multiple times.   The argument uses a form similar to the `--volume` option of the `docker run` command:  `source:dest`.   Overlays are applied recursively onto the destination in a similar manner to `cp -rv`.   If multiple overlays are specified, they are applied in the order in which they were listed on the command line.  
+
+Overlays are used to replace entire sets of files with alternative content, whereas templates allow environment substitutions into a single file.  The example below assumes that /tmp/overlays has already been COPY'd into the image by the Dockerfile.
+
+```
+$ dockerize  -overlay "/tmp/overlays/_common/html:/usr/share/nginx/" \
+             -overlay "/tmp/overlays/{{ .Env.DEPLOYMENT_ENV }}/html:/usr/share/nginx/"
+```
+
 You can tail multiple files to `STDOUT` and `STDERR` by passing the options multiple times.
 
 ```

dockerize.go

@@ -8,6 +8,7 @@ import (
 	"net/http"
 	"net/url"
 	"os"
+	"os/exec"
 	"strings"
 	"sync"
 	"time"
@@ -18,18 +19,6 @@ import (
 type sliceVar []string
 type hostFlagsVar []string
 
-type Context struct {
-}
-
-func (c *Context) Env() map[string]string {
-	env := make(map[string]string)
-	for _, i := range os.Environ() {
-		sep := strings.Index(i, "=")
-		env[i[0:sep]] = i[sep+1:]
-	}
-	return env
-}
-
 var (
 	buildVersion string
 	version      bool
@@ -39,6 +28,7 @@ var (
 	templatesFlag   sliceVar
 	stdoutTailFlag  sliceVar
 	stderrTailFlag  sliceVar
+	overlaysFlag    sliceVar
 	delimsFlag      string
 	delims          []string
 	waitFlag        hostFlagsVar
@@ -70,6 +60,10 @@ func (s *sliceVar) String() string {
 func waitForDependencies() {
 	dependencyChan := make(chan struct{})
 
+	if waitFlag == nil {
+		return
+	}
+
 	go func() {
 		for _, host := range waitFlag {
 			log.Println("Waiting for host:", host)
@@ -104,7 +98,7 @@ func waitForDependencies() {
 					}
 				}()
 			default:
-				log.Fatalf("invalid host protocol provided: %s. supported protocols are: tcp, tcp4, tcp6 and http", u.Scheme)
+				log.Fatalf("invalid host protocol provided: %s. supported protocols are: tcp, tcp4, tcp6, http and https", u.Scheme)
 			}
 		}
 		wg.Wait()
@@ -139,7 +133,9 @@ Arguments:
    and /var/log/nginx/error.log, waiting for a website to become available on port 8000 and start nginx.`)
 	println(`
    dockerize -template nginx.tmpl:/etc/nginx/nginx.conf \
-             -stdout /var/log/nginx/access.log \
+   	     -overlay overlays/_common/html:/usr/share/nginx/ \
+   	     -overlay overlays/{{ .Env.DEPLOYMENT_ENV }}/html:/usr/share/nginx/ \`)
+	println(`   	     -stdout /var/log/nginx/access.log \
              -stderr /var/log/nginx/error.log \
              -wait tcp://web:8000 nginx
 	`)
@@ -152,6 +148,7 @@ func main() {
 	flag.BoolVar(&version, "version", false, "show version")
 	flag.BoolVar(&poll, "poll", false, "enable polling")
 	flag.Var(&templatesFlag, "template", "Template (/template:/dest). Can be passed multiple times")
+	flag.Var(&overlaysFlag, "overlay", "overlay (/src:/dest). Can be passed multiple times")
 	flag.Var(&stdoutTailFlag, "stdout", "Tails a file to stdout. Can be passed multiple times")
 	flag.Var(&stderrTailFlag, "stderr", "Tails a file to stderr. Can be passed multiple times")
 	flag.StringVar(&delimsFlag, "delims", "", `template tag delimiters. default "{{":"}}" `)
@@ -177,14 +174,34 @@ func main() {
 			log.Fatalf("bad delimiters argument: %s. expected \"left:right\"", delimsFlag)
 		}
 	}
+
+	// Overlay files from src --> dst
+	for _, o := range overlaysFlag {
+		if strings.Contains(o, ":") {
+			parts := strings.Split(o, ":")
+			if len(parts) != 2 {
+				log.Fatalf("bad overlay argument: '%s'. expected \"/src:/dest\"", o)
+			}
+			src, dest := string_template_eval(parts[0]), string_template_eval(parts[1])
+
+			log.Printf("overlaying %s --> %s", src, dest)
+
+			cmd := exec.Command("cp", "-rv", src, dest)
+			cmd.Stdout, cmd.Stderr = os.Stdout, os.Stderr
+			if err := cmd.Run(); err != nil {
+				log.Fatal(err)
+			}
+		}
+	}
+
 	for _, t := range templatesFlag {
 		template, dest := t, ""
 		if strings.Contains(t, ":") {
 			parts := strings.Split(t, ":")
 			if len(parts) != 2 {
 				log.Fatalf("bad template argument: %s. expected \"/template:/dest\"", t)
 			}
-			template, dest = parts[0], parts[1]
+			template, dest = string_template_eval(parts[0]), string_template_eval(parts[1])
 		}
 		generateFile(template, dest)
 	}

examples/nginx/.gitignore

@@ -0,0 +1 @@
+*.gz

examples/nginx/Dockerfile

@@ -1,20 +1,31 @@
-FROM ubuntu:14.04
+FROM nginx:1.9
 MAINTAINER Jason Wilder mail@jasonwilder.com
 
-# Install Nginx.
-RUN echo "deb http://ppa.launchpad.net/nginx/stable/ubuntu trusty main" > /etc/apt/sources.list.d/nginx-stable-trusty.list
-RUN echo "deb-src http://ppa.launchpad.net/nginx/stable/ubuntu trusty main" >> /etc/apt/sources.list.d/nginx-stable-trusty.list
-RUN apt-key adv --keyserver keyserver.ubuntu.com --recv-keys C300EE8C
-RUN apt-get update
-RUN apt-get install -y  wget nginx
+# RUN wget https://github.com/markriggins/dockerize/releases/download/v0.2.0/dockerize-linux-amd64-v0.0.4.tar.gz
+# RUN tar -C /usr/local/bin -xvzf dockerize-linux-amd64-v0.2.0.tar.gz
 
-RUN wget https://github.com/jwilder/dockerize/releases/download/v0.0.4/dockerize-linux-amd64-v0.0.4.tar.gz
-RUN tar -C /usr/local/bin -xvzf dockerize-linux-amd64-v0.0.4.tar.gz
+COPY .dockerize_linux_amd64.tar.gz /tmp/
+RUN  cd /usr/local/bin && \
+    tar -xzv --strip-components=1 -f /tmp/.d*.gz dockerize_linux_amd64/dockerize && \
+    rm /tmp/.d*.gz
 
-RUN echo "daemon off;" >> /etc/nginx/nginx.conf
-
-ADD default.tmpl /etc/nginx/sites-available/default.tmpl
+COPY default.tmpl /etc/nginx/sites-available/default.tmpl
+COPY overlays /tmp/overlays
 
 EXPOSE 80
 
-CMD ["dockerize", "-template", "/etc/nginx/sites-available/default.tmpl:/etc/nginx/sites-available/default", "-stdout", "/var/log/nginx/access.log", "-stderr", "/var/log/nginx/error.log", "nginx"]
+ENV DEPLOYMENT_ENV=staging
+
+#  These options do not work well on virtualbox osx -- it pegs one CPU
+#     "-poll", \
+#     "-stdout", "/var/log/nginx/access.log", \
+#     "-stderr", "/var/log/nginx/error.log", \
+
+CMD [ "dockerize", \
+     "-template", "/etc/nginx/sites-available/default.tmpl:/etc/nginx/sites-available/default", \
+     "-overlay", "/tmp/overlays/_common/html:/usr/share/nginx/", \
+     "-overlay", "/tmp/overlays/{{ .Env.DEPLOYMENT_ENV }}/html:/usr/share/nginx/", \
+     "-poll", \
+     "-stdout", "/var/log/nginx/access.log", \
+     "-stderr", "/var/log/nginx/error.log", \
+     "--", "nginx", "-g", "daemon off;"]

examples/nginx/Makefile

@@ -0,0 +1,18 @@
+.PHONY : build run-staging run-prod
+
+build: 
+	cd ../..; goxc -os linux -arch amd64
+	cp -f $(shell bash -xc 'find $(GOPATH)/bin -name dockerize_linux_amd64.tar.gz| head -1') .dockerize_linux_amd64.tar.gz
+	docker build -t dockerized-nginx .
+	rm .dockerize_linux_amd64.tar.gz
+
+
+run-staging: 
+	docker rm -f dockerized-nginx 2>/dev/null || true
+	docker run -d -p 80:80 -e DEPLOYMENT_ENV=staging --name dockerized-nginx dockerized-nginx
+	open http://$(shell docker-machine ip $(shell docker-machine active))/robots.txt
+
+run-prod: 
+	docker rm -f dockerized-nginx 2>/dev/null || true
+	docker run -d -p 80:80 -e DEPLOYMENT_ENV=prod --name dockerized-nginx dockerized-nginx
+	open http://$(shell docker-machine ip $(shell docker-machine active))/robots.txt

examples/nginx/overlays/_common/html/robots.txt

@@ -0,0 +1,5 @@
+#
+# Common robots.txt file
+#
+User-agent: *
+Disallow: /

examples/nginx/overlays/prod/html/robots.txt

@@ -0,0 +1,5 @@
+#
+# Prod robots.txt file
+#
+User-agent: *
+Allow: /

template.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"bytes"
 	"fmt"
 	"log"
 	"net/url"
@@ -12,6 +13,18 @@ import (
 	"text/template"
 )
 
+type EnvContext struct {
+}
+
+func (c *EnvContext) Env() map[string]string {
+	env := make(map[string]string)
+	for _, i := range os.Environ() {
+		sep := strings.Index(i, "=")
+		env[i[0:sep]] = i[sep+1:]
+	}
+	return env
+}
+
 func exists(path string) (bool, error) {
 	_, err := os.Stat(path)
 	if err == nil {
@@ -68,6 +81,30 @@ func add(arg1, arg2 int) int {
 	return arg1 + arg2
 }
 
+//
+// Execute the string_template under the EnvContext, and
+// return the result as a string
+//
+func string_template_eval(string_template string) string {
+	var result bytes.Buffer
+	t := template.New("String Template")
+
+	t, err := t.Parse(string_template)
+	if err != nil {
+		log.Fatalf("unable to parse template: %s", err)
+	}
+
+	err = t.Execute(&result, &EnvContext{})
+	if err != nil {
+		log.Fatalf("template error: %s\n", err)
+	}
+
+	return result.String()
+}
+
+//
+// Execute the template at templatePath under the EnvContext and write it to destPath
+//
 func generateFile(templatePath, destPath string) bool {
 	tmpl := template.New(filepath.Base(templatePath)).Funcs(template.FuncMap{
 		"contains": contains,
@@ -97,7 +134,7 @@ func generateFile(templatePath, destPath string) bool {
 		defer dest.Close()
 	}
 
-	err = tmpl.ExecuteTemplate(dest, filepath.Base(templatePath), &Context{})
+	err = tmpl.ExecuteTemplate(dest, filepath.Base(templatePath), &EnvContext{})
 	if err != nil {
 		log.Fatalf("template error: %s\n", err)
 	}