From 7df6bacee59cf2f11bceee646e385d6c5a0d0b36 Mon Sep 17 00:00:00 2001
From: Alex <alexellis2@gmail.com>
Date: Sun, 9 Oct 2016 19:49:34 +0100
Subject: [PATCH] Allow dind image to be overriden.

- improve readme - mention pre-pulling dind image.
- read env variable once in init() method
---
 README.md            |  6 +++++-
 services/docker.go   |  8 +-------
 services/instance.go | 26 ++++++++++++++++++++++----
 3 files changed, 28 insertions(+), 12 deletions(-)

diff --git a/README.md b/README.md
index 3c0aea5..59ab094 100644
--- a/README.md
+++ b/README.md
@@ -9,6 +9,8 @@ A live version is available at: http://play-with-docker.com/
 
 ## Installation
 
+Start the Docker daemon on your machine and run `docker pull docker:1.12.2-rc2-dind`. 
+
 1) Install go 1.7.1 with `brew` on Mac or through a package manager.
 
 2) `go get`
@@ -21,5 +23,7 @@ A live version is available at: http://play-with-docker.com/
 
 Notes:
 
-There is a hard-coded limit to 5 Docker playgrounds per session. After 1 hour sessions are deleted.
+* There is a hard-coded limit to 5 Docker playgrounds per session. After 1 hour sessions are deleted.
+* If you want to override the DIND version or image then set the environmental variable i.e.
+  `DIND_IMAGE=docker:dind`
 
diff --git a/services/docker.go b/services/docker.go
index 21ea4f8..49306d9 100644
--- a/services/docker.go
+++ b/services/docker.go
@@ -2,7 +2,6 @@ package services
 
 import (
 	"log"
-	"os"
 	"strings"
 
 	ptypes "github.com/franela/play-with-docker/types"
@@ -75,18 +74,13 @@ func AttachExecConnection(execId string, ctx context.Context) (*types.HijackedRe
 	return &conn, nil
 }
 
-func CreateInstance(net string) (*ptypes.Instance, error) {
+func CreateInstance(net string, dindImage string) (*ptypes.Instance, error) {
 
 	var maximumPidLimit int64
 	maximumPidLimit = 150 // Set a ulimit value to prevent misuse
 	h := &container.HostConfig{NetworkMode: container.NetworkMode(net), Privileged: true}
 	h.Resources.PidsLimit = maximumPidLimit
 
-	dindImage := os.Getenv("DIND_IMAGE")
-	if len(dindImage) == 0 {
-		dindImage = "docker:1.12.2-rc2-dind"
-	}
-
 	conf := &container.Config{Image: dindImage}
 	container, err := c.ContainerCreate(context.Background(), conf, h, nil, "")
 
diff --git a/services/instance.go b/services/instance.go
index 949f27d..e95b8e2 100644
--- a/services/instance.go
+++ b/services/instance.go
@@ -1,19 +1,37 @@
 package services
 
-import "github.com/franela/play-with-docker/types"
+import (
+	"log"
+	"os"
+
+	"github.com/franela/play-with-docker/types"
+)
 
 var instances map[string]map[string]*types.Instance
 
+var dindImage string
+var defaultDindImageName string
+
 func init() {
 	instances = make(map[string]map[string]*types.Instance)
+        dindImage = getDindImageName()
+}
+
+func getDindImageName() string {
+	dindImage := os.Getenv("DIND_IMAGE")
+        defaultDindImageName = "docker:1.12.2-rc2-dind"
+        if len(dindImage) == 0 {
+		dindImage = defaultDindImageName
+	}
+	return dindImage
 }
 
 func NewInstance(session *types.Session) (*types.Instance, error) {
-	//TODO: Validate that a session can only have 10 instances
 
+	//TODO: Validate that a session can only have 5 instances
 	//TODO: Create in redis
-
-	instance, err := CreateInstance(session.Id)
+	log.Printf("NewInstance - using image: [%s]\n", dindImage)
+	instance, err := CreateInstance(session.Id, dindImage)
 
 	if err != nil {
 		return nil, err