Allow overriding an image's entrypoint in Docker

client/driver/docker.go

@@ -177,6 +177,7 @@ type DockerDriverConfig struct {
 	LoadImage        string              `mapstructure:"load"`               // LoadImage is a path to an image archive file
 	Command          string              `mapstructure:"command"`            // The Command to run when the container starts up
 	Args             []string            `mapstructure:"args"`               // The arguments to the Command
+	Entrypoint       []string            `mapstructure:"entrypoint"`         // Override the containers entrypoint
 	IpcMode          string              `mapstructure:"ipc_mode"`           // The IPC mode of the container - host and none
 	NetworkMode      string              `mapstructure:"network_mode"`       // The network mode of the container - host, nat and none
 	NetworkAliases   []string            `mapstructure:"network_aliases"`    // The network-scoped alias for the container
@@ -299,6 +300,7 @@ func NewDockerDriverConfig(task *structs.Task, env *env.TaskEnv) (*DockerDriverC
 	// Interpolate everything that is a string
 	dconf.ImageName = env.ReplaceEnv(dconf.ImageName)
 	dconf.Command = env.ReplaceEnv(dconf.Command)
+	dconf.Entrypoint = env.ParseAndReplace(dconf.Entrypoint)
 	dconf.IpcMode = env.ReplaceEnv(dconf.IpcMode)
 	dconf.NetworkMode = env.ReplaceEnv(dconf.NetworkMode)
 	dconf.NetworkAliases = env.ParseAndReplace(dconf.NetworkAliases)
@@ -559,6 +561,9 @@ func (d *DockerDriver) Validate(config map[string]interface{}) error {
 			"args": {
 				Type: fields.TypeArray,
 			},
+			"entrypoint": {
+				Type: fields.TypeArray,
+			},
 			"ipc_mode": {
 				Type: fields.TypeString,
 			},
@@ -1070,6 +1075,7 @@ func (d *DockerDriver) createContainerConfig(ctx *ExecContext, task *structs.Tas
 	// create the config block that will later be consumed by go-dockerclient
 	config := &docker.Config{
 		Image:       d.imageID,
+		Entrypoint:  driverConfig.Entrypoint,
 		Hostname:    driverConfig.Hostname,
 		User:        task.User,
 		Tty:         driverConfig.TTY,

client/driver/docker_test.go

@@ -28,6 +28,7 @@ import (
 	"github.com/hashicorp/nomad/nomad/structs"
 	tu "github.com/hashicorp/nomad/testutil"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func dockerIsRemote(t *testing.T) bool {
@@ -106,13 +107,14 @@ func testDockerDriverContexts(t *testing.T, task *structs.Task) *testContext {
 func dockerSetupWithClient(t *testing.T, task *structs.Task, client *docker.Client) (*docker.Client, *DockerHandle, func()) {
 	t.Helper()
 	tctx := testDockerDriverContexts(t, task)
-	//tctx.DriverCtx.config.Options = map[string]string{"docker.cleanup.image": "false"}
 	driver := NewDockerDriver(tctx.DriverCtx)
 	copyImage(t, tctx.ExecCtx.TaskDir, "busybox.tar")
 
 	presp, err := driver.Prestart(tctx.ExecCtx, task)
 	if err != nil {
-		driver.Cleanup(tctx.ExecCtx, presp.CreatedResources)
+		if presp != nil && presp.CreatedResources != nil {
+			driver.Cleanup(tctx.ExecCtx, presp.CreatedResources)
+		}
 		tctx.AllocDir.Destroy()
 		t.Fatalf("error in prestart: %v", err)
 	}
@@ -2171,7 +2173,32 @@ func TestDockerDriver_Device_Success(t *testing.T) {
 
 	assert.NotEmpty(t, container.HostConfig.Devices, "Expected one device")
 	assert.Equal(t, expectedDevice, container.HostConfig.Devices[0], "Incorrect device ")
+}
+
+func TestDockerDriver_Entrypoint(t *testing.T) {
+	if !tu.IsTravis() {
+		t.Parallel()
+	}
+	if !testutil.DockerIsConnected(t) {
+		t.Skip("Docker not connected")
+	}
+
+	entrypoint := []string{"/bin/sh", "-c"}
+	task, _, _ := dockerTask(t)
+	task.Config["entrypoint"] = entrypoint
+
+	client, handle, cleanup := dockerSetup(t, task)
+	defer cleanup()
+
+	waitForExist(t, client, handle)
+
+	container, err := client.InspectContainer(handle.ContainerID())
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
 
+	require.Len(t, container.Config.Entrypoint, 2, "Expected one entrypoint")
+	require.Equal(t, entrypoint, container.Config.Entrypoint, "Incorrect entrypoint ")
 }
 
 func TestDockerDriver_Kill(t *testing.T) {

client/driver/env/env.go

@@ -162,6 +162,10 @@ func (t *TaskEnv) All() map[string]string {
 // ParseAndReplace takes the user supplied args replaces any instance of an
 // environment variable or Nomad variable in the args with the actual value.
 func (t *TaskEnv) ParseAndReplace(args []string) []string {
+	if args == nil {
+		return nil
+	}
+
 	replaced := make([]string, len(args))
 	for i, arg := range args {
 		replaced[i] = hargs.ReplaceEnv(arg, t.EnvMap, t.NodeAttrs)

website/source/docs/drivers/docker.html.md

@@ -83,6 +83,8 @@ The `docker` driver supports the following configuration in the job spec.  Only
 * `dns_servers` - (Optional) A list of DNS servers for the container to use
   (e.g. ["8.8.8.8", "8.8.4.4"]). Requires Docker v1.10 or greater.
 
+* `entrypoint` - (Optional) A string list overriding the image's entrypoint.
+
 * `extra_hosts` - (Optional) A list of hosts, given as host:IP, to be added to
   `/etc/hosts`.