enable use of docker-standard DOCKER_HOST environment variable to allow drone to run builds on remote docker hosts.

pkg/build/docker/client.go

@@ -32,15 +32,8 @@ var Logging = true
 // New creates an instance of the Docker Client
 func New() *Client {
 	c := &Client{}
-	c.proto = DEFAULTPROTOCOL
-	c.addr = DEFAULTUNIXSOCKET
 
-	// if the default socket doesn't exist then
-	// we'll try to connect to the default tcp address
-	if _, err := os.Stat(DEFAULTUNIXSOCKET); err != nil {
-		c.proto = "tcp"
-		c.addr = "0.0.0.0:4243"
-	}
+	c.setHost(DEFAULTUNIXSOCKET)
 
 	c.Images = &ImageService{c}
 	c.Containers = &ContainerService{c}
@@ -76,6 +69,26 @@ var (
 	ErrBadRequest = errors.New("Bad Request")
 )
 
+func (c *Client) setHost(defaultUnixSocket string) {
+	c.proto = DEFAULTPROTOCOL
+	c.addr = defaultUnixSocket
+
+	if os.Getenv("DOCKER_HOST") != "" {
+		pieces := strings.Split(os.Getenv("DOCKER_HOST"), "://")
+		if len(pieces) == 2 {
+			c.proto = pieces[0]
+			c.addr = pieces[1]
+		}
+	} else {
+		// if the default socket doesn't exist then
+		// we'll try to connect to the default tcp address
+		if _, err := os.Stat(defaultUnixSocket); err != nil {
+			c.proto = "tcp"
+			c.addr = "0.0.0.0:4243"
+		}
+	}
+}
+
 // helper function used to make HTTP requests to the Docker daemon.
 func (c *Client) do(method, path string, in, out interface{}) error {
 	// if data input is provided, serialize to JSON

pkg/build/docker/client_test.go

@@ -0,0 +1,67 @@
+package docker
+
+import (
+	"io/ioutil"
+	"os"
+	"testing"
+)
+
+func TestHostFromEnv(t *testing.T) {
+	os.Setenv("DOCKER_HOST", "tcp://1.1.1.1:4243")
+	defer os.Setenv("DOCKER_HOST", "")
+
+	client := New()
+
+	if client.proto != "tcp" {
+		t.Fail()
+	}
+
+	if client.addr != "1.1.1.1:4243" {
+		t.Fail()
+	}
+}
+
+func TestInvalidHostFromEnv(t *testing.T) {
+	os.Setenv("DOCKER_HOST", "tcp:1.1.1.1:4243") // missing tcp:// prefix
+	defer os.Setenv("DOCKER_HOST", "")
+
+	client := New()
+
+	if client.addr == "1.1.1.1:4243" {
+		t.Fail()
+	}
+}
+
+func TestSocketHost(t *testing.T) {
+	// create temporary file to represent the docker socket
+	file, err := ioutil.TempFile("", "TestDefaultUnixHost")
+	if err != nil {
+		t.Fail()
+	}
+	file.Close()
+	defer os.Remove(file.Name())
+
+	client := &Client{}
+	client.setHost(file.Name())
+
+	if client.proto != "unix" {
+		t.Fail()
+	}
+
+	if client.addr != file.Name() {
+		t.Fail()
+	}
+}
+
+func TestDefaultTcpHost(t *testing.T) {
+	client := &Client{}
+	client.setHost("/tmp/missing_socket")
+
+	if client.proto != "tcp" {
+		t.Fail()
+	}
+
+	if client.addr != "0.0.0.0:4243" {
+		t.Fail()
+	}
+}