Mount task_local and alloc dir to docker containers

client/alloc_runner.go

@@ -282,7 +282,11 @@ func (r *AllocRunner) Run() {
 	// Create the execution context
 	if r.ctx == nil {
 		allocDir := allocdir.NewAllocDir(filepath.Join(r.config.AllocDir, r.alloc.ID))
-		allocDir.Build(tg.Tasks)
+		if err := allocDir.Build(tg.Tasks); err != nil {
+			r.logger.Printf("[WARN] client: failed to build task directories: %v", err)
+			r.setStatus(structs.AllocClientStatusFailed, fmt.Sprintf("failed to build task dirs for '%s'", alloc.TaskGroup))
+			return
+		}
 		r.ctx = driver.NewExecContext(allocDir)
 	}
 

client/driver/docker.go

@@ -4,12 +4,15 @@ import (
 	"encoding/json"
 	"fmt"
 	"log"
+	"path/filepath"
 	"strconv"
 	"strings"
 
 	docker "github.com/fsouza/go-dockerclient"
 
+	"github.com/hashicorp/nomad/client/allocdir"
 	"github.com/hashicorp/nomad/client/config"
+	"github.com/hashicorp/nomad/client/driver/args"
 	"github.com/hashicorp/nomad/nomad/structs"
 )
 
@@ -97,12 +100,33 @@ func (d *DockerDriver) Fingerprint(cfg *config.Config, node *structs.Node) (bool
 	return true, nil
 }
 
-// We have to call this when we create the container AND when we start it so
-// we'll make a function.
-func createHostConfig(task *structs.Task) *docker.HostConfig {
-	// hostConfig holds options for the docker container that are unique to this
-	// machine, such as resource limits and port mappings
-	return &docker.HostConfig{
+func containerBinds(alloc *allocdir.AllocDir, task *structs.Task) ([]string, error) {
+	shared := alloc.SharedDir
+	local, ok := alloc.TaskDirs[task.Name]
+	if !ok {
+		return nil, fmt.Errorf("Failed to find task local directory: %v", task.Name)
+	}
+
+	return []string{
+		fmt.Sprintf("%s:%s", shared, allocdir.SharedAllocName),
+		fmt.Sprintf("%s:%s", local, allocdir.TaskLocal),
+	}, nil
+}
+
+// createContainer initializes a struct needed to call docker.client.CreateContainer()
+func createContainer(ctx *ExecContext, task *structs.Task, logger *log.Logger) (docker.CreateContainerOptions, error) {
+	var c docker.CreateContainerOptions
+	if task.Resources == nil {
+		logger.Printf("[ERR] driver.docker: task.Resources is empty")
+		return c, fmt.Errorf("task.Resources is nil and we can't constrain resource usage. We shouldn't have been able to schedule this in the first place.")
+	}
+
+	binds, err := containerBinds(ctx.AllocDir, task)
+	if err != nil {
+		return c, err
+	}
+
+	hostConfig := &docker.HostConfig{
 		// Convert MB to bytes. This is an absolute value.
 		//
 		// This value represents the total amount of memory a process can use.
@@ -131,20 +155,16 @@ func createHostConfig(task *structs.Task) *docker.HostConfig {
 		//  - https://www.kernel.org/doc/Documentation/scheduler/sched-bwc.txt
 		//  - https://www.kernel.org/doc/Documentation/scheduler/sched-design-CFS.txt
 		CPUShares: int64(task.Resources.CPU),
-	}
-}
 
-// createContainer initializes a struct needed to call docker.client.CreateContainer()
-func createContainer(ctx *ExecContext, task *structs.Task, logger *log.Logger) (docker.CreateContainerOptions, error) {
-	var c docker.CreateContainerOptions
-	if task.Resources == nil {
-		logger.Printf("[ERR] driver.docker: task.Resources is empty")
-		return c, fmt.Errorf("task.Resources is nil and we can't constrain resource usage. We shouldn't have been able to schedule this in the first place.")
+		// Binds are used to mount a host volume into the container. We mount a
+		// local directory for storage and a shared alloc directory that can be
+		// used to share data between different tasks in the same task group.
+		Binds: binds,
 	}
 
-	hostConfig := createHostConfig(task)
 	logger.Printf("[DEBUG] driver.docker: using %d bytes memory for %s", hostConfig.Memory, task.Config["image"])
 	logger.Printf("[DEBUG] driver.docker: using %d cpu shares for %s", hostConfig.CPUShares, task.Config["image"])
+	logger.Printf("[DEBUG] driver.docker: binding directories %#v for %s", hostConfig.Binds, task.Config["image"])
 
 	mode, ok := task.Config["network_mode"]
 	if !ok || mode == "" {
@@ -198,14 +218,31 @@ func createContainer(ctx *ExecContext, task *structs.Task, logger *log.Logger) (
 		hostConfig.PortBindings = dockerPorts
 	}
 
+	// Create environment variables.
+	env := TaskEnvironmentVariables(ctx, task)
+	env.SetAllocDir(filepath.Join("/", allocdir.SharedAllocName))
+	env.SetTaskLocalDir(filepath.Join("/", allocdir.TaskLocal))
+
 	config := &docker.Config{
-		Env:   TaskEnvironmentVariables(ctx, task).List(),
+		Env:   env.List(),
 		Image: task.Config["image"],
 	}
 
+	rawArgs, hasArgs := task.Config["args"]
+	parsedArgs, err := args.ParseAndReplace(rawArgs, env.Map())
+	if err != nil {
+		return c, err
+	}
+
 	// If the user specified a custom command to run, we'll inject it here.
 	if command, ok := task.Config["command"]; ok {
-		config.Cmd = strings.Split(command, " ")
+		cmd := []string{command}
+		if hasArgs {
+			cmd = append(cmd, parsedArgs...)
+		}
+		config.Cmd = cmd
+	} else if hasArgs {
+		logger.Println("[DEBUG] driver.docker: ignoring args because command not specified")
 	}
 
 	return docker.CreateContainerOptions{

client/driver/docker_test.go

@@ -1,11 +1,16 @@
 package driver
 
 import (
+	"fmt"
+	"io/ioutil"
 	"os/exec"
+	"path/filepath"
+	"reflect"
 	"testing"
 	"time"
 
 	"github.com/hashicorp/nomad/client/config"
+	"github.com/hashicorp/nomad/client/driver/environment"
 	"github.com/hashicorp/nomad/nomad/structs"
 )
 
@@ -102,7 +107,8 @@ func TestDockerDriver_Start_Wait(t *testing.T) {
 		Name: "redis-demo",
 		Config: map[string]string{
 			"image":   "redis",
-			"command": "redis-server -v",
+			"command": "redis-server",
+			"args":    "-v",
 		},
 		Resources: &structs.Resources{
 			MemoryMB: 256,
@@ -140,6 +146,61 @@ func TestDockerDriver_Start_Wait(t *testing.T) {
 	}
 }
 
+func TestDockerDriver_Start_Wait_AllocDir(t *testing.T) {
+	if !dockerLocated() {
+		t.SkipNow()
+	}
+
+	exp := []byte{'w', 'i', 'n'}
+	file := "output.txt"
+	task := &structs.Task{
+		Name: "redis-demo",
+		Config: map[string]string{
+			"image":   "redis",
+			"command": "/bin/bash",
+			"args":    fmt.Sprintf(`-c "sleep 1; echo -n %s > $%s/%s"`, string(exp), environment.AllocDir, file),
+		},
+		Resources: &structs.Resources{
+			MemoryMB: 256,
+			CPU:      512,
+		},
+	}
+
+	driverCtx := testDockerDriverContext(task.Name)
+	ctx := testDriverExecContext(task, driverCtx)
+	defer ctx.AllocDir.Destroy()
+	d := NewDockerDriver(driverCtx)
+
+	handle, err := d.Start(ctx, task)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	if handle == nil {
+		t.Fatalf("missing handle")
+	}
+	defer handle.Kill()
+
+	select {
+	case err := <-handle.WaitCh():
+		if err != nil {
+			t.Fatalf("err: %v", err)
+		}
+	case <-time.After(5 * time.Second):
+		t.Fatalf("timeout")
+	}
+
+	// Check that data was written to the shared alloc directory.
+	outputFile := filepath.Join(ctx.AllocDir.SharedDir, file)
+	act, err := ioutil.ReadFile(outputFile)
+	if err != nil {
+		t.Fatalf("Couldn't read expected output: %v", err)
+	}
+
+	if !reflect.DeepEqual(act, exp) {
+		t.Fatalf("Command outputted %v; want %v", act, exp)
+	}
+}
+
 func TestDockerDriver_Start_Kill_Wait(t *testing.T) {
 	if !dockerLocated() {
 		t.SkipNow()
@@ -149,7 +210,8 @@ func TestDockerDriver_Start_Kill_Wait(t *testing.T) {
 		Name: "redis-demo",
 		Config: map[string]string{
 			"image":   "redis",
-			"command": "sleep 10",
+			"command": "/bin/sleep",
+			"args":    "10",
 		},
 		Resources: basicResources,
 	}
@@ -188,6 +250,7 @@ func TestDockerDriver_Start_Kill_Wait(t *testing.T) {
 
 func taskTemplate() *structs.Task {
 	return &structs.Task{
+		Name: "redis-demo",
 		Config: map[string]string{
 			"image": "redis",
 		},
@@ -242,6 +305,11 @@ func TestDocker_StartN(t *testing.T) {
 	t.Log("==> All tasks are started. Terminating...")
 
 	for idx, handle := range handles {
+		if handle == nil {
+			t.Errorf("Bad handle for task #%d", idx+1)
+			continue
+		}
+
 		err := handle.Kill()
 		if err != nil {
 			t.Errorf("Failed stopping task #%d: %s", idx+1, err)
@@ -291,6 +359,11 @@ func TestDocker_StartNVersions(t *testing.T) {
 	t.Log("==> All tasks are started. Terminating...")
 
 	for idx, handle := range handles {
+		if handle == nil {
+			t.Errorf("Bad handle for task #%d", idx+1)
+			continue
+		}
+
 		err := handle.Kill()
 		if err != nil {
 			t.Errorf("Failed stopping task #%d: %s", idx+1, err)
@@ -306,6 +379,7 @@ func TestDockerHostNet(t *testing.T) {
 	}
 
 	task := &structs.Task{
+		Name: "redis-demo",
 		Config: map[string]string{
 			"image":        "redis",
 			"network_mode": "host",

client/driver/environment/vars.go

@@ -12,6 +12,10 @@ const (
 	// group.
 	AllocDir = "NOMAD_ALLOC_DIR"
 
+	// The path to the tasks local directory where it can store data that is
+	// persisted to the alloc is removed.
+	TaskLocalDir = "NOMAD_TASK_DIR"
+
 	// The tasks memory limit in MBs.
 	MemLimit = "NOMAD_MEMORY_LIMIT"
 
@@ -70,6 +74,10 @@ func (t TaskEnvironment) SetAllocDir(dir string) {
 	t[AllocDir] = dir
 }
 
+func (t TaskEnvironment) SetTaskLocalDir(dir string) {
+	t[TaskLocalDir] = dir
+}
+
 func (t TaskEnvironment) SetMemLimit(limit int) {
 	t[MemLimit] = strconv.Itoa(limit)
 }

client/driver/exec_test.go

@@ -85,7 +85,7 @@ func TestExecDriver_Start_Wait(t *testing.T) {
 		Name: "sleep",
 		Config: map[string]string{
 			"command": "/bin/sleep",
-			"args":    "1",
+			"args":    "2",
 		},
 		Resources: basicResources,
 	}
@@ -115,7 +115,7 @@ func TestExecDriver_Start_Wait(t *testing.T) {
 		if err != nil {
 			t.Fatalf("err: %v", err)
 		}
-	case <-time.After(2 * time.Second):
+	case <-time.After(4 * time.Second):
 		t.Fatalf("timeout")
 	}
 }

client/fingerprint/host.go

@@ -5,7 +5,7 @@ import (
 	"log"
 	"os/exec"
 	"runtime"
-        "strings"
+	"strings"
 
 	"github.com/hashicorp/nomad/client/config"
 	"github.com/hashicorp/nomad/nomad/structs"

scripts/build.sh

@@ -44,6 +44,7 @@ gox \
     -arch="${XC_ARCH}" \
     -osarch="!linux/arm !darwin/386" \
     -ldflags "-X main.GitCommit ${GIT_COMMIT}${GIT_DIRTY}" \
+    -cgo \
     -output "pkg/{{.OS}}_{{.Arch}}/nomad" \
     .
 

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

@@ -23,6 +23,9 @@ The `docker` driver supports the following configuration in the job specificatio
 
 * `command` - (Optional) The command to run when starting the container.
 
+* `args` - (Optional) Arguments to the optional `command`. If no `command` is
+  present, `args` are ignored.
+
 * `network_mode` - (Optional) The network mode to be used for the container.
    Valid options are `default`, `bridge`, `host` or `none`. If nothing is
    specified, the container will start in `bridge` mode. The `container`

website/source/docs/jobspec/environment.html.md

@@ -56,6 +56,27 @@ exported as environment variables for consistency, e.g. `NOMAD_PORT_5000`.
 
 Please see the relevant driver documentation for details.
 
+### Task Directories
+
+Nomad makes the following two directories available to tasks:
+
+* `alloc/`: This directory is shared across all tasks in a task group and can be
+  used to store data that needs to be used by multiple tasks, such as a log
+  shipper.
+* `local/`: This directory is private to each task. It can be used to store
+  arbitrary data that shouldn't be shared by tasks in the task group.
+
+Both these directories are persisted until the allocation is removed, which
+occurs hours after all the tasks in the task group enter terminal states. This
+gives time to view the data produced by tasks.
+
+Depending on the driver and operating system being targeted, the directories are
+made available in various ways. For example, on `docker` the directories are
+binded to the container, while on `exec` on Linux the directories are mounted into the
+chroot. Regardless of how the directories are made available, the path to the
+directories can be read through the following environment variables:
+`NOMAD_ALLOC_DIR` and `NOMAD_TASK_DIR`.
+
 ## Meta
 
 The job specification also allows you to specify a `meta` block to supply arbitrary