From 5127e75569132bb8568b4e566b091d46944a2811 Mon Sep 17 00:00:00 2001
From: Matt Mercer <mamercer@cisco.com>
Date: Tue, 17 Oct 2017 17:54:22 -0700
Subject: [PATCH 01/12] Qemu driver: add graceful shutdown feature

---
 client/driver/qemu.go                    |  99 ++++++++++++++++++----
 client/driver/qemu_test.go               | 100 ++++++++++++++++-------
 website/source/docs/drivers/qemu.html.md |   9 +-
 3 files changed, 159 insertions(+), 49 deletions(-)

diff --git a/client/driver/qemu.go b/client/driver/qemu.go
index 1d1f11695..17b137257 100644
--- a/client/driver/qemu.go
+++ b/client/driver/qemu.go
@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"log"
+	"net"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -13,7 +14,8 @@ import (
 	"strings"
 	"time"
 
-	"github.com/hashicorp/go-plugin"
+	"github.com/coreos/go-semver/semver"
+	plugin "github.com/hashicorp/go-plugin"
 	"github.com/hashicorp/nomad/client/config"
 	"github.com/hashicorp/nomad/client/driver/executor"
 	dstructs "github.com/hashicorp/nomad/client/driver/structs"
@@ -29,9 +31,14 @@ var (
 )
 
 const (
-	// The key populated in Node Attributes to indicate presence of the Qemu
-	// driver
-	qemuDriverAttr = "driver.qemu"
+	// The key populated in Node Attributes to indicate presence of the Qemu driver
+	qemuDriverAttr                = "driver.qemu"
+	qemuDriverVersionAttr         = "driver.qemu.version"
+	qemuDriverLongMonitorPathAttr = "driver.qemu.longsocketpaths"
+	// Represents an ACPI shutdown request to the VM (emulates pressing a physical power button)
+	// Reference: https://en.wikibooks.org/wiki/QEMU/Monitor
+	qemuGracefulShutdownMsg = "system_powerdown\n"
+	legacyMaxMonitorPathLen = 108
 )
 
 // QemuDriver is a driver for running images via Qemu
@@ -45,10 +52,11 @@ type QemuDriver struct {
 }
 
 type QemuDriverConfig struct {
-	ImagePath   string           `mapstructure:"image_path"`
-	Accelerator string           `mapstructure:"accelerator"`
-	PortMap     []map[string]int `mapstructure:"port_map"` // A map of host port labels and to guest ports.
-	Args        []string         `mapstructure:"args"`     // extra arguments to qemu executable
+	ImagePath        string           `mapstructure:"image_path"`
+	Accelerator      string           `mapstructure:"accelerator"`
+	GracefulShutdown bool             `mapstructure:"graceful_shutdown"`
+	PortMap          []map[string]int `mapstructure:"port_map"` // A map of host port labels and to guest ports.
+	Args             []string         `mapstructure:"args"`     // extra arguments to qemu executable
 }
 
 // qemuHandle is returned from Start/Open as a handle to the PID
@@ -56,6 +64,7 @@ type qemuHandle struct {
 	pluginClient   *plugin.Client
 	userPid        int
 	executor       executor.Executor
+	monitorPath    string
 	killTimeout    time.Duration
 	maxKillTimeout time.Duration
 	logger         *log.Logger
@@ -64,6 +73,13 @@ type qemuHandle struct {
 	doneCh         chan struct{}
 }
 
+func getMonitorPath(dir string, longPathSupport string) (string, error) {
+	if len(dir) > legacyMaxMonitorPathLen && longPathSupport != "1" {
+		return "", fmt.Errorf("monitor path is too long")
+	}
+	return fmt.Sprintf("%s/qemu-monitor.sock", dir), nil
+}
+
 // NewQemuDriver is used to create a new exec driver
 func NewQemuDriver(ctx *DriverContext) Driver {
 	return &QemuDriver{DriverContext: *ctx}
@@ -81,6 +97,10 @@ func (d *QemuDriver) Validate(config map[string]interface{}) error {
 			"accelerator": {
 				Type: fields.TypeString,
 			},
+			"graceful_shutdown": {
+				Type:     fields.TypeBool,
+				Required: false,
+			},
 			"port_map": {
 				Type: fields.TypeArray,
 			},
@@ -129,7 +149,23 @@ func (d *QemuDriver) Fingerprint(cfg *config.Config, node *structs.Node) (bool,
 	}
 
 	node.Attributes[qemuDriverAttr] = "1"
-	node.Attributes["driver.qemu.version"] = matches[1]
+	node.Attributes[qemuDriverVersionAttr] = matches[1]
+
+	// Prior to qemu 2.10.1, monitor socket paths are truncated to 108 bytes.
+	// We should consider this if driver.qemu.version is < 2.10.1 and the
+	// generated monitor path is too long.
+	//
+	// Relevant fix is here:
+	// https://github.com/qemu/qemu/commit/ad9579aaa16d5b385922d49edac2c96c79bcfb6
+	currentVer := semver.New(matches[1])
+	fixedSocketPathLenVer := semver.New("2.10.1")
+	if currentVer.LessThan(*fixedSocketPathLenVer) {
+		node.Attributes[qemuDriverLongMonitorPathAttr] = "0"
+		d.logger.Printf("[DEBUG] driver.qemu - long socket paths are not available in this version of QEMU")
+	} else {
+		d.logger.Printf("[DEBUG] driver.qemu - long socket paths available in this version of QEMU")
+		node.Attributes[qemuDriverLongMonitorPathAttr] = "1"
+	}
 	return true, nil
 }
 
@@ -190,6 +226,19 @@ func (d *QemuDriver) Start(ctx *ExecContext, task *structs.Task) (*StartResponse
 		"-nographic",
 	}
 
+	var monitorPath string
+	if d.driverConfig.GracefulShutdown {
+		// This socket will be used to manage the virtual machine (for example,
+		// to perform graceful shutdowns)
+		monitorPath, err = getMonitorPath(ctx.TaskDir.Dir, ctx.TaskEnv.NodeAttrs[qemuDriverLongMonitorPathAttr])
+		if err == nil {
+			d.logger.Printf("[DEBUG] driver.qemu - got monitor path OK: %s", monitorPath)
+			args = append(args, "-monitor", fmt.Sprintf("unix:%s,server,nowait", monitorPath))
+		} else {
+			d.logger.Printf("[WARN] driver.qemu - %s", err)
+		}
+	}
+
 	// Add pass through arguments to qemu executable. A user can specify
 	// these arguments in driver task configuration. These arguments are
 	// passed directly to the qemu driver as command line options.
@@ -239,7 +288,7 @@ func (d *QemuDriver) Start(ctx *ExecContext, task *structs.Task) (*StartResponse
 		)
 	}
 
-	d.logger.Printf("[DEBUG] Starting QemuVM command: %q", strings.Join(args, " "))
+	d.logger.Printf("[DEBUG] driver.qemu - starting QemuVM command: %q", strings.Join(args, " "))
 	pluginLogFile := filepath.Join(ctx.TaskDir.Dir, "executor.out")
 	executorConfig := &dstructs.ExecutorConfig{
 		LogFile:  pluginLogFile,
@@ -272,7 +321,7 @@ func (d *QemuDriver) Start(ctx *ExecContext, task *structs.Task) (*StartResponse
 		pluginClient.Kill()
 		return nil, err
 	}
-	d.logger.Printf("[INFO] Started new QemuVM: %s", vmID)
+	d.logger.Printf("[INFO] driver.qemu - started new QemuVM: %s", vmID)
 
 	// Create and Return Handle
 	maxKill := d.DriverContext.config.MaxKillTimeout
@@ -282,6 +331,7 @@ func (d *QemuDriver) Start(ctx *ExecContext, task *structs.Task) (*StartResponse
 		userPid:        ps.Pid,
 		killTimeout:    GetKillTimeout(task.KillTimeout, maxKill),
 		maxKillTimeout: maxKill,
+		monitorPath:    monitorPath,
 		version:        d.config.Version.VersionNumber(),
 		logger:         d.logger,
 		doneCh:         make(chan struct{}),
@@ -317,7 +367,7 @@ func (d *QemuDriver) Open(ctx *ExecContext, handleID string) (DriverHandle, erro
 
 	exec, pluginClient, err := createExecutorWithConfig(pluginConfig, d.config.LogOutput)
 	if err != nil {
-		d.logger.Println("[ERR] driver.qemu: error connecting to plugin so destroying plugin pid and user pid")
+		d.logger.Println("[ERR] driver.qemu - error connecting to plugin so destroying plugin pid and user pid")
 		if e := destroyPlugin(id.PluginConfig.Pid, id.UserPid); e != nil {
 			d.logger.Printf("[ERR] driver.qemu: error destroying plugin and userpid: %v", e)
 		}
@@ -381,9 +431,26 @@ func (h *qemuHandle) Signal(s os.Signal) error {
 	return fmt.Errorf("Qemu driver can't send signals")
 }
 
-// TODO: allow a 'shutdown_command' that can be executed over a ssh connection
-// to the VM
 func (h *qemuHandle) Kill() error {
+	// If a graceful shutdown was requested at task start time,
+	// monitorPath will not be empty
+	if h.monitorPath != "" {
+		monitorSocket, err := net.Dial("unix", h.monitorPath)
+		if err == nil {
+			defer monitorSocket.Close()
+			h.logger.Printf("[DEBUG] driver.qemu - sending graceful shutdown command to qemu monitor socket at %s", h.monitorPath)
+			_, err = monitorSocket.Write([]byte(qemuGracefulShutdownMsg))
+			if err == nil {
+				return nil
+			}
+			h.logger.Printf("[WARN] driver.qemu - failed to send '%s' to monitor socket '%s': %s", qemuGracefulShutdownMsg, h.monitorPath, err)
+		} else {
+			// OK, that didn't work - we'll continue on and
+			// attempt to kill the process as a last resort
+			h.logger.Printf("[WARN] driver.qemu - could not connect to qemu monitor at %s: %s", h.monitorPath, err)
+		}
+	}
+
 	if err := h.executor.ShutDown(); err != nil {
 		if h.pluginClient.Exited() {
 			return nil
@@ -395,13 +462,13 @@ func (h *qemuHandle) Kill() error {
 	case <-h.doneCh:
 		return nil
 	case <-time.After(h.killTimeout):
+		h.logger.Printf("[DEBUG] driver.qemu - kill timeout exceeded")
 		if h.pluginClient.Exited() {
 			return nil
 		}
 		if err := h.executor.Exit(); err != nil {
 			return fmt.Errorf("executor Exit failed: %v", err)
 		}
-
 		return nil
 	}
 }
@@ -414,7 +481,7 @@ func (h *qemuHandle) run() {
 	ps, werr := h.executor.Wait()
 	if ps.ExitCode == 0 && werr != nil {
 		if e := killProcess(h.userPid); e != nil {
-			h.logger.Printf("[ERR] driver.qemu: error killing user process: %v", e)
+			h.logger.Printf("[ERR] driver.qemu - error killing user process: %v", e)
 		}
 	}
 	close(h.doneCh)
diff --git a/client/driver/qemu_test.go b/client/driver/qemu_test.go
index 98d491d3d..646fd3d71 100644
--- a/client/driver/qemu_test.go
+++ b/client/driver/qemu_test.go
@@ -14,6 +14,14 @@ import (
 	ctestutils "github.com/hashicorp/nomad/client/testutil"
 )
 
+func generateString(length int) string {
+	var newString string
+	for i := 0; i < length; i++ {
+		newString = newString + "x"
+	}
+	return string(newString)
+}
+
 // The fingerprinter test should always pass, even if QEMU is not installed.
 func TestQemuDriver_Fingerprint(t *testing.T) {
 	if !testutil.IsTravis() {
@@ -39,12 +47,15 @@ func TestQemuDriver_Fingerprint(t *testing.T) {
 	if !apply {
 		t.Fatalf("should apply")
 	}
-	if node.Attributes["driver.qemu"] == "" {
+	if node.Attributes[qemuDriverAttr] == "" {
 		t.Fatalf("Missing Qemu driver")
 	}
-	if node.Attributes["driver.qemu.version"] == "" {
+	if node.Attributes[qemuDriverVersionAttr] == "" {
 		t.Fatalf("Missing Qemu driver version")
 	}
+	if node.Attributes[qemuDriverLongMonitorPathAttr] == "" {
+		t.Fatalf("Missing Qemu long monitor socket path support flag")
+	}
 }
 
 func TestQemuDriver_StartOpen_Wait(t *testing.T) {
@@ -56,8 +67,9 @@ func TestQemuDriver_StartOpen_Wait(t *testing.T) {
 		Name:   "linux",
 		Driver: "qemu",
 		Config: map[string]interface{}{
-			"image_path":  "linux-0.2.img",
-			"accelerator": "tcg",
+			"image_path":        "linux-0.2.img",
+			"accelerator":       "tcg",
+			"graceful_shutdown": true,
 			"port_map": []map[string]int{{
 				"main": 22,
 				"web":  8080,
@@ -85,10 +97,11 @@ func TestQemuDriver_StartOpen_Wait(t *testing.T) {
 
 	// Copy the test image into the task's directory
 	dst := ctx.ExecCtx.TaskDir.Dir
+
 	copyFile("./test-resources/qemu/linux-0.2.img", filepath.Join(dst, "linux-0.2.img"), t)
 
 	if _, err := d.Prestart(ctx.ExecCtx, task); err != nil {
-		t.Fatalf("Prestart faild: %v", err)
+		t.Fatalf("Prestart failed: %v", err)
 	}
 
 	resp, err := d.Start(ctx.ExecCtx, task)
@@ -121,34 +134,36 @@ func TestQemuDriverUser(t *testing.T) {
 		t.Parallel()
 	}
 	ctestutils.QemuCompatible(t)
-	tasks := []*structs.Task{{
-		Name:   "linux",
-		Driver: "qemu",
-		User:   "alice",
-		Config: map[string]interface{}{
-			"image_path":  "linux-0.2.img",
-			"accelerator": "tcg",
-			"port_map": []map[string]int{{
-				"main": 22,
-				"web":  8080,
-			}},
-			"args": []string{"-nodefconfig", "-nodefaults"},
-			"msg":  "unknown user alice",
-		},
-		LogConfig: &structs.LogConfig{
-			MaxFiles:      10,
-			MaxFileSizeMB: 10,
-		},
-		Resources: &structs.Resources{
-			CPU:      500,
-			MemoryMB: 512,
-			Networks: []*structs.NetworkResource{
-				{
-					ReservedPorts: []structs.Port{{Label: "main", Value: 22000}, {Label: "web", Value: 80}},
+	tasks := []*structs.Task{
+		{
+			Name:   "linux",
+			Driver: "qemu",
+			User:   "alice",
+			Config: map[string]interface{}{
+				"image_path":        "linux-0.2.img",
+				"accelerator":       "tcg",
+				"graceful_shutdown": false,
+				"port_map": []map[string]int{{
+					"main": 22,
+					"web":  8080,
+				}},
+				"args": []string{"-nodefconfig", "-nodefaults"},
+				"msg":  "unknown user alice",
+			},
+			LogConfig: &structs.LogConfig{
+				MaxFiles:      10,
+				MaxFileSizeMB: 10,
+			},
+			Resources: &structs.Resources{
+				CPU:      500,
+				MemoryMB: 512,
+				Networks: []*structs.NetworkResource{
+					{
+						ReservedPorts: []structs.Port{{Label: "main", Value: 22000}, {Label: "web", Value: 80}},
+					},
 				},
 			},
 		},
-	},
 		{
 			Name:   "linux",
 			Driver: "qemu",
@@ -193,9 +208,34 @@ func TestQemuDriverUser(t *testing.T) {
 			resp.Handle.Kill()
 			t.Fatalf("Should've failed")
 		}
+
 		msg := task.Config["msg"].(string)
 		if !strings.Contains(err.Error(), msg) {
 			t.Fatalf("Expecting '%v' in '%v'", msg, err)
 		}
 	}
 }
+
+func TestQemuDriverGetMonitorPath(t *testing.T) {
+	shortPath := generateString(10)
+	_, err := getMonitorPath(shortPath, "0")
+	if err != nil {
+		t.Fatal("Should not have returned an error")
+	}
+
+	longPath := generateString(legacyMaxMonitorPathLen + 100)
+	_, err = getMonitorPath(longPath, "0")
+	if err == nil {
+		t.Fatal("Should have returned an error")
+	}
+	_, err = getMonitorPath(longPath, "1")
+	if err != nil {
+		t.Fatal("Should not have returned an error")
+	}
+
+	maxLengthPath := generateString(legacyMaxMonitorPathLen)
+	_, err = getMonitorPath(maxLengthPath, "0")
+	if err != nil {
+		t.Fatal("Should not have returned an error")
+	}
+}
diff --git a/website/source/docs/drivers/qemu.html.md b/website/source/docs/drivers/qemu.html.md
index 14490de06..c26d6e82f 100644
--- a/website/source/docs/drivers/qemu.html.md
+++ b/website/source/docs/drivers/qemu.html.md
@@ -29,9 +29,10 @@ task "webservice" {
   driver = "qemu"
 
   config {
-    image_path  = "/path/to/my/linux.img"
-    accelerator = "kvm"
-    args        = ["-nodefaults", "-nodefconfig"]
+    image_path        = "/path/to/my/linux.img"
+    accelerator       = "kvm"
+    graceful_shutdown = true
+    args              = ["-nodefaults", "-nodefconfig"]
   }
 }  
 ```
@@ -47,6 +48,8 @@ The `qemu` driver supports the following configuration in the job spec:
   If the host machine has `qemu` installed with KVM support, users can specify
   `kvm` for the `accelerator`. Default is `tcg`.
 
+* `graceful_shutdown` `(bool: false)` - Using the [qemu monitor](https://en.wikibooks.org/wiki/QEMU/Monitor), send an ACPI shutdown signal to virtual machines rather than simply terminating them. This emulates a physical power button press, and gives instances a chance to shut down cleanly. If the VM is still running after ``kill_timeout``, it will be forcefully terminated. (Note that [prior to qemu 2.10.1](https://github.com/qemu/qemu/commit/ad9579aaa16d5b385922d49edac2c96c79bcfb6), the monitor socket path is limited to 108 characters. Graceful shutdown will be disabled if qemu is < 2.10.1 and the generated monitor path exceeds this length. You may encounter this issue if you set long [data_dir](https://www.nomadproject.io/docs/agent/configuration/index.html#data_dir) or [alloc_dir](https://www.nomadproject.io/docs/agent/configuration/client.html#alloc_dir) paths.)
+
 * `port_map` - (Optional) A key-value map of port labels.
 
     ```hcl

From 4afb9dfa2d191762696d2556e532a57372dda907 Mon Sep 17 00:00:00 2001
From: Matt Mercer <mgordonmercer+github@gmail.com>
Date: Mon, 30 Oct 2017 20:10:18 -0700
Subject: [PATCH 02/12] Standardize driver.qemu logging prefix

---
 client/driver/qemu.go | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/client/driver/qemu.go b/client/driver/qemu.go
index 17b137257..7212a1e93 100644
--- a/client/driver/qemu.go
+++ b/client/driver/qemu.go
@@ -161,9 +161,9 @@ func (d *QemuDriver) Fingerprint(cfg *config.Config, node *structs.Node) (bool,
 	fixedSocketPathLenVer := semver.New("2.10.1")
 	if currentVer.LessThan(*fixedSocketPathLenVer) {
 		node.Attributes[qemuDriverLongMonitorPathAttr] = "0"
-		d.logger.Printf("[DEBUG] driver.qemu - long socket paths are not available in this version of QEMU")
+		d.logger.Printf("[DEBUG] driver.qemu: long socket paths are not available in this version of QEMU")
 	} else {
-		d.logger.Printf("[DEBUG] driver.qemu - long socket paths available in this version of QEMU")
+		d.logger.Printf("[DEBUG] driver.qemu: long socket paths available in this version of QEMU")
 		node.Attributes[qemuDriverLongMonitorPathAttr] = "1"
 	}
 	return true, nil
@@ -232,10 +232,10 @@ func (d *QemuDriver) Start(ctx *ExecContext, task *structs.Task) (*StartResponse
 		// to perform graceful shutdowns)
 		monitorPath, err = getMonitorPath(ctx.TaskDir.Dir, ctx.TaskEnv.NodeAttrs[qemuDriverLongMonitorPathAttr])
 		if err == nil {
-			d.logger.Printf("[DEBUG] driver.qemu - got monitor path OK: %s", monitorPath)
+			d.logger.Printf("[DEBUG] driver.qemu: got monitor path OK: %s", monitorPath)
 			args = append(args, "-monitor", fmt.Sprintf("unix:%s,server,nowait", monitorPath))
 		} else {
-			d.logger.Printf("[WARN] driver.qemu - %s", err)
+			d.logger.Printf("[WARN] driver.qemu: %s", err)
 		}
 	}
 
@@ -288,7 +288,7 @@ func (d *QemuDriver) Start(ctx *ExecContext, task *structs.Task) (*StartResponse
 		)
 	}
 
-	d.logger.Printf("[DEBUG] driver.qemu - starting QemuVM command: %q", strings.Join(args, " "))
+	d.logger.Printf("[DEBUG] driver.qemu: starting QemuVM command: %q", strings.Join(args, " "))
 	pluginLogFile := filepath.Join(ctx.TaskDir.Dir, "executor.out")
 	executorConfig := &dstructs.ExecutorConfig{
 		LogFile:  pluginLogFile,
@@ -321,7 +321,7 @@ func (d *QemuDriver) Start(ctx *ExecContext, task *structs.Task) (*StartResponse
 		pluginClient.Kill()
 		return nil, err
 	}
-	d.logger.Printf("[INFO] driver.qemu - started new QemuVM: %s", vmID)
+	d.logger.Printf("[INFO] driver.qemu: started new QemuVM: %s", vmID)
 
 	// Create and Return Handle
 	maxKill := d.DriverContext.config.MaxKillTimeout
@@ -367,7 +367,7 @@ func (d *QemuDriver) Open(ctx *ExecContext, handleID string) (DriverHandle, erro
 
 	exec, pluginClient, err := createExecutorWithConfig(pluginConfig, d.config.LogOutput)
 	if err != nil {
-		d.logger.Println("[ERR] driver.qemu - error connecting to plugin so destroying plugin pid and user pid")
+		d.logger.Println("[ERR] driver.qemu: error connecting to plugin so destroying plugin pid and user pid")
 		if e := destroyPlugin(id.PluginConfig.Pid, id.UserPid); e != nil {
 			d.logger.Printf("[ERR] driver.qemu: error destroying plugin and userpid: %v", e)
 		}
@@ -438,16 +438,16 @@ func (h *qemuHandle) Kill() error {
 		monitorSocket, err := net.Dial("unix", h.monitorPath)
 		if err == nil {
 			defer monitorSocket.Close()
-			h.logger.Printf("[DEBUG] driver.qemu - sending graceful shutdown command to qemu monitor socket at %s", h.monitorPath)
+			h.logger.Printf("[DEBUG] driver.qemu: sending graceful shutdown command to qemu monitor socket at %s", h.monitorPath)
 			_, err = monitorSocket.Write([]byte(qemuGracefulShutdownMsg))
 			if err == nil {
 				return nil
 			}
-			h.logger.Printf("[WARN] driver.qemu - failed to send '%s' to monitor socket '%s': %s", qemuGracefulShutdownMsg, h.monitorPath, err)
+			h.logger.Printf("[WARN] driver.qemu: failed to send '%s' to monitor socket '%s': %s", qemuGracefulShutdownMsg, h.monitorPath, err)
 		} else {
 			// OK, that didn't work - we'll continue on and
 			// attempt to kill the process as a last resort
-			h.logger.Printf("[WARN] driver.qemu - could not connect to qemu monitor at %s: %s", h.monitorPath, err)
+			h.logger.Printf("[WARN] driver.qemu: could not connect to qemu monitor at %s: %s", h.monitorPath, err)
 		}
 	}
 
@@ -462,7 +462,7 @@ func (h *qemuHandle) Kill() error {
 	case <-h.doneCh:
 		return nil
 	case <-time.After(h.killTimeout):
-		h.logger.Printf("[DEBUG] driver.qemu - kill timeout exceeded")
+		h.logger.Printf("[DEBUG] driver.qemu: kill timeout exceeded")
 		if h.pluginClient.Exited() {
 			return nil
 		}
@@ -481,7 +481,7 @@ func (h *qemuHandle) run() {
 	ps, werr := h.executor.Wait()
 	if ps.ExitCode == 0 && werr != nil {
 		if e := killProcess(h.userPid); e != nil {
-			h.logger.Printf("[ERR] driver.qemu - error killing user process: %v", e)
+			h.logger.Printf("[ERR] driver.qemu: error killing user process: %v", e)
 		}
 	}
 	close(h.doneCh)

From 47c832972e3740bf7be58d1a63ae2fd77cae5bfe Mon Sep 17 00:00:00 2001
From: Matt Mercer <mgordonmercer+github@gmail.com>
Date: Mon, 30 Oct 2017 20:19:25 -0700
Subject: [PATCH 03/12] Wrap qemu docs at 80 characters

---
 website/source/docs/drivers/qemu.html.md | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/website/source/docs/drivers/qemu.html.md b/website/source/docs/drivers/qemu.html.md
index c26d6e82f..3f78c202e 100644
--- a/website/source/docs/drivers/qemu.html.md
+++ b/website/source/docs/drivers/qemu.html.md
@@ -48,7 +48,20 @@ The `qemu` driver supports the following configuration in the job spec:
   If the host machine has `qemu` installed with KVM support, users can specify
   `kvm` for the `accelerator`. Default is `tcg`.
 
-* `graceful_shutdown` `(bool: false)` - Using the [qemu monitor](https://en.wikibooks.org/wiki/QEMU/Monitor), send an ACPI shutdown signal to virtual machines rather than simply terminating them. This emulates a physical power button press, and gives instances a chance to shut down cleanly. If the VM is still running after ``kill_timeout``, it will be forcefully terminated. (Note that [prior to qemu 2.10.1](https://github.com/qemu/qemu/commit/ad9579aaa16d5b385922d49edac2c96c79bcfb6), the monitor socket path is limited to 108 characters. Graceful shutdown will be disabled if qemu is < 2.10.1 and the generated monitor path exceeds this length. You may encounter this issue if you set long [data_dir](https://www.nomadproject.io/docs/agent/configuration/index.html#data_dir) or [alloc_dir](https://www.nomadproject.io/docs/agent/configuration/client.html#alloc_dir) paths.)
+* `graceful_shutdown` `(bool: false)` - Using the [qemu
+  monitor](https://en.wikibooks.org/wiki/QEMU/Monitor), send an ACPI shutdown
+  signal to virtual machines rather than simply terminating them. This emulates
+  a physical power button press, and gives instances a chance to shut down
+  cleanly. If the VM is still running after ``kill_timeout``, it will be
+  forcefully terminated. (Note that
+  [prior to qemu 2.10.1](https://github.com/qemu/qemu/commit/ad9579aaa16d5b385922d49edac2c96c79bcfb6),
+  the monitor socket path is limited to 108 characters. Graceful shutdown will
+  be disabled if qemu is < 2.10.1 and the generated monitor path exceeds this
+  length. You may encounter this issue if you set long
+  [data_dir](https://www.nomadproject.io/docs/agent/configuration/index.html#data_dir)
+  or
+  [alloc_dir](https://www.nomadproject.io/docs/agent/configuration/client.html#alloc_dir)
+  paths.)
 
 * `port_map` - (Optional) A key-value map of port labels.
 

From 46f7e2fa4c7d258224b9379bebc9838f0c06e99b Mon Sep 17 00:00:00 2001
From: Matt Mercer <mgordonmercer+github@gmail.com>
Date: Mon, 30 Oct 2017 20:20:31 -0700
Subject: [PATCH 04/12] Qemu driver: minor logging fixes

---
 client/driver/qemu.go | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/client/driver/qemu.go b/client/driver/qemu.go
index 7212a1e93..e77f68189 100644
--- a/client/driver/qemu.go
+++ b/client/driver/qemu.go
@@ -147,9 +147,10 @@ func (d *QemuDriver) Fingerprint(cfg *config.Config, node *structs.Node) (bool,
 		delete(node.Attributes, qemuDriverAttr)
 		return false, fmt.Errorf("Unable to parse Qemu version string: %#v", matches)
 	}
+	currentQemuVersion := matches[1]
 
 	node.Attributes[qemuDriverAttr] = "1"
-	node.Attributes[qemuDriverVersionAttr] = matches[1]
+	node.Attributes[qemuDriverVersionAttr] = currentQemuVersion
 
 	// Prior to qemu 2.10.1, monitor socket paths are truncated to 108 bytes.
 	// We should consider this if driver.qemu.version is < 2.10.1 and the
@@ -157,13 +158,13 @@ func (d *QemuDriver) Fingerprint(cfg *config.Config, node *structs.Node) (bool,
 	//
 	// Relevant fix is here:
 	// https://github.com/qemu/qemu/commit/ad9579aaa16d5b385922d49edac2c96c79bcfb6
-	currentVer := semver.New(matches[1])
+	currentQemuSemver := semver.New(currentQemuVersion)
 	fixedSocketPathLenVer := semver.New("2.10.1")
-	if currentVer.LessThan(*fixedSocketPathLenVer) {
+	if currentQemuSemver.LessThan(*fixedSocketPathLenVer) {
 		node.Attributes[qemuDriverLongMonitorPathAttr] = "0"
-		d.logger.Printf("[DEBUG] driver.qemu: long socket paths are not available in this version of QEMU")
+		d.logger.Printf("[DEBUG] driver.qemu: long socket paths are not available in this version of QEMU (%s)", currentQemuVersion)
 	} else {
-		d.logger.Printf("[DEBUG] driver.qemu: long socket paths available in this version of QEMU")
+		d.logger.Printf("[DEBUG] driver.qemu: long socket paths available in this version of QEMU (%s)", currentQemuVersion)
 		node.Attributes[qemuDriverLongMonitorPathAttr] = "1"
 	}
 	return true, nil
@@ -358,7 +359,7 @@ type qemuId struct {
 func (d *QemuDriver) Open(ctx *ExecContext, handleID string) (DriverHandle, error) {
 	id := &qemuId{}
 	if err := json.Unmarshal([]byte(handleID), id); err != nil {
-		return nil, fmt.Errorf("Failed to parse handle '%s': %v", handleID, err)
+		return nil, fmt.Errorf("Failed to parse handle %q: %v", handleID, err)
 	}
 
 	pluginConfig := &plugin.ClientConfig{
@@ -367,9 +368,9 @@ func (d *QemuDriver) Open(ctx *ExecContext, handleID string) (DriverHandle, erro
 
 	exec, pluginClient, err := createExecutorWithConfig(pluginConfig, d.config.LogOutput)
 	if err != nil {
-		d.logger.Println("[ERR] driver.qemu: error connecting to plugin so destroying plugin pid and user pid")
+		d.logger.Printf("[ERR] driver.qemu: error connecting to plugin so destroying plugin pid %d and user pid %d", id.PluginConfig.Pid, id.UserPid)
 		if e := destroyPlugin(id.PluginConfig.Pid, id.UserPid); e != nil {
-			d.logger.Printf("[ERR] driver.qemu: error destroying plugin and userpid: %v", e)
+			d.logger.Printf("[ERR] driver.qemu: error destroying plugin pid %d and userpid %d: %v", id.PluginConfig.Pid, id.UserPid, e)
 		}
 		return nil, fmt.Errorf("error connecting to plugin: %v", err)
 	}
@@ -438,16 +439,16 @@ func (h *qemuHandle) Kill() error {
 		monitorSocket, err := net.Dial("unix", h.monitorPath)
 		if err == nil {
 			defer monitorSocket.Close()
-			h.logger.Printf("[DEBUG] driver.qemu: sending graceful shutdown command to qemu monitor socket at %s", h.monitorPath)
+			h.logger.Printf("[DEBUG] driver.qemu: sending graceful shutdown command to qemu monitor socket %q", h.monitorPath)
 			_, err = monitorSocket.Write([]byte(qemuGracefulShutdownMsg))
 			if err == nil {
 				return nil
 			}
-			h.logger.Printf("[WARN] driver.qemu: failed to send '%s' to monitor socket '%s': %s", qemuGracefulShutdownMsg, h.monitorPath, err)
+			h.logger.Printf("[WARN] driver.qemu: failed to send %q to monitor socket %q: %s", qemuGracefulShutdownMsg, h.monitorPath, err)
 		} else {
 			// OK, that didn't work - we'll continue on and
 			// attempt to kill the process as a last resort
-			h.logger.Printf("[WARN] driver.qemu: could not connect to qemu monitor at %s: %s", h.monitorPath, err)
+			h.logger.Printf("[WARN] driver.qemu: could not connect to qemu monitor %q: %s", h.monitorPath, err)
 		}
 	}
 

From 38d9a391aaa2961a9c7cbe71766087b44bcac8ec Mon Sep 17 00:00:00 2001
From: Matt Mercer <mgordonmercer+github@gmail.com>
Date: Mon, 30 Oct 2017 23:03:36 -0700
Subject: [PATCH 05/12] Qemu driver: ensure proper cleanup of resources

---
 client/driver/qemu.go | 54 ++++++++++++++++++++++++++-----------------
 1 file changed, 33 insertions(+), 21 deletions(-)

diff --git a/client/driver/qemu.go b/client/driver/qemu.go
index e77f68189..12867cdf4 100644
--- a/client/driver/qemu.go
+++ b/client/driver/qemu.go
@@ -3,6 +3,7 @@ package driver
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"log"
 	"net"
@@ -433,32 +434,24 @@ func (h *qemuHandle) Signal(s os.Signal) error {
 }
 
 func (h *qemuHandle) Kill() error {
-	// If a graceful shutdown was requested at task start time,
-	// monitorPath will not be empty
-	if h.monitorPath != "" {
-		monitorSocket, err := net.Dial("unix", h.monitorPath)
-		if err == nil {
-			defer monitorSocket.Close()
-			h.logger.Printf("[DEBUG] driver.qemu: sending graceful shutdown command to qemu monitor socket %q", h.monitorPath)
-			_, err = monitorSocket.Write([]byte(qemuGracefulShutdownMsg))
-			if err == nil {
+	// First, try sending a graceful shutdown command via the qemu monitor
+	err := h.sendQemuShutdown()
+
+	// If we couldn't send a graceful shutdown via the monitor socket, we'll
+	// issue an interrupt to the qemu process as a last resort
+	if err != nil {
+		if err := h.executor.ShutDown(); err != nil {
+			if h.pluginClient.Exited() {
 				return nil
 			}
-			h.logger.Printf("[WARN] driver.qemu: failed to send %q to monitor socket %q: %s", qemuGracefulShutdownMsg, h.monitorPath, err)
-		} else {
-			// OK, that didn't work - we'll continue on and
-			// attempt to kill the process as a last resort
-			h.logger.Printf("[WARN] driver.qemu: could not connect to qemu monitor %q: %s", h.monitorPath, err)
+			return fmt.Errorf("executor Shutdown failed: %v", err)
 		}
 	}
 
-	if err := h.executor.ShutDown(); err != nil {
-		if h.pluginClient.Exited() {
-			return nil
-		}
-		return fmt.Errorf("executor Shutdown failed: %v", err)
-	}
-
+	// At this point, we're waiting for the qemu process to exit. If we've
+	// attempted a graceful shutdown and the guest shuts down in time, doneChan
+	// will close and we'll exit without an error. If it takes too long, the
+	// timer will fire and we'll attempt to kill the process.
 	select {
 	case <-h.doneCh:
 		return nil
@@ -495,3 +488,22 @@ func (h *qemuHandle) run() {
 	h.waitCh <- &dstructs.WaitResult{ExitCode: ps.ExitCode, Signal: ps.Signal, Err: werr}
 	close(h.waitCh)
 }
+
+func (h *qemuHandle) sendQemuShutdown() error {
+	var err error
+	if h.monitorPath == "" {
+		err = errors.New("monitorPath not set")
+	} else {
+		monitorSocket, err := net.Dial("unix", h.monitorPath)
+		if err == nil {
+			defer monitorSocket.Close()
+			h.logger.Printf("[DEBUG] driver.qemu: sending graceful shutdown command to qemu monitor socket %q", h.monitorPath)
+			_, err = monitorSocket.Write([]byte(qemuGracefulShutdownMsg))
+			if err != nil {
+				h.logger.Printf("[WARN] driver.qemu: failed to send shutdown message %q to monitor socket %q: %s", qemuGracefulShutdownMsg, h.monitorPath, err)
+			}
+		}
+		h.logger.Printf("[WARN] driver.qemu: could not connect to qemu monitor %q: %s", h.monitorPath, err)
+	}
+	return err
+}

From c26013ea0b08c3912867b3ef54dddc5a67eab4eb Mon Sep 17 00:00:00 2001
From: Matt Mercer <mgordonmercer+github@gmail.com>
Date: Wed, 1 Nov 2017 10:41:48 -0700
Subject: [PATCH 06/12] Qemu driver: include PIDs in log output

---
 client/driver/qemu.go | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/client/driver/qemu.go b/client/driver/qemu.go
index 12867cdf4..e053ec094 100644
--- a/client/driver/qemu.go
+++ b/client/driver/qemu.go
@@ -456,7 +456,7 @@ func (h *qemuHandle) Kill() error {
 	case <-h.doneCh:
 		return nil
 	case <-time.After(h.killTimeout):
-		h.logger.Printf("[DEBUG] driver.qemu: kill timeout exceeded")
+		h.logger.Printf("[DEBUG] driver.qemu: kill timeout exceeded for user process pid %d", h.userPid)
 		if h.pluginClient.Exited() {
 			return nil
 		}
@@ -475,7 +475,7 @@ func (h *qemuHandle) run() {
 	ps, werr := h.executor.Wait()
 	if ps.ExitCode == 0 && werr != nil {
 		if e := killProcess(h.userPid); e != nil {
-			h.logger.Printf("[ERR] driver.qemu: error killing user process: %v", e)
+			h.logger.Printf("[ERR] driver.qemu: error killing user process pid %d: %v", h.userPid, e)
 		}
 	}
 	close(h.doneCh)
@@ -497,13 +497,13 @@ func (h *qemuHandle) sendQemuShutdown() error {
 		monitorSocket, err := net.Dial("unix", h.monitorPath)
 		if err == nil {
 			defer monitorSocket.Close()
-			h.logger.Printf("[DEBUG] driver.qemu: sending graceful shutdown command to qemu monitor socket %q", h.monitorPath)
+			h.logger.Printf("[DEBUG] driver.qemu: sending graceful shutdown command to qemu monitor socket %q for user process pid %d", h.monitorPath, h.userPid)
 			_, err = monitorSocket.Write([]byte(qemuGracefulShutdownMsg))
 			if err != nil {
-				h.logger.Printf("[WARN] driver.qemu: failed to send shutdown message %q to monitor socket %q: %s", qemuGracefulShutdownMsg, h.monitorPath, err)
+				h.logger.Printf("[WARN] driver.qemu: failed to send shutdown message %q to monitor socket %q for user process pid %d: %s", qemuGracefulShutdownMsg, h.monitorPath, h.userPid, err)
 			}
 		}
-		h.logger.Printf("[WARN] driver.qemu: could not connect to qemu monitor %q: %s", h.monitorPath, err)
+		h.logger.Printf("[WARN] driver.qemu: could not connect to qemu monitor %q for user process pid %d: %s", h.monitorPath, h.userPid, err)
 	}
 	return err
 }

From d51d174fa0fad3a8066282b8c7c379bca8764a58 Mon Sep 17 00:00:00 2001
From: Matt Mercer <mgordonmercer+github@gmail.com>
Date: Wed, 1 Nov 2017 14:47:14 -0700
Subject: [PATCH 07/12] Qemu driver: basic testing of graceful shutdown feature

---
 client/driver/qemu.go      | 28 +++++++-----
 client/driver/qemu_test.go | 94 +++++++++++++++++++++++++++++++++++++-
 2 files changed, 109 insertions(+), 13 deletions(-)

diff --git a/client/driver/qemu.go b/client/driver/qemu.go
index e053ec094..5ad11b9f2 100644
--- a/client/driver/qemu.go
+++ b/client/driver/qemu.go
@@ -40,6 +40,7 @@ const (
 	// Reference: https://en.wikibooks.org/wiki/QEMU/Monitor
 	qemuGracefulShutdownMsg = "system_powerdown\n"
 	legacyMaxMonitorPathLen = 108
+	qemuMonitorSocketName   = "qemu-monitor.sock"
 )
 
 // QemuDriver is a driver for running images via Qemu
@@ -78,7 +79,7 @@ func getMonitorPath(dir string, longPathSupport string) (string, error) {
 	if len(dir) > legacyMaxMonitorPathLen && longPathSupport != "1" {
 		return "", fmt.Errorf("monitor path is too long")
 	}
-	return fmt.Sprintf("%s/qemu-monitor.sock", dir), nil
+	return fmt.Sprintf("%s/%s", dir, qemuMonitorSocketName), nil
 }
 
 // NewQemuDriver is used to create a new exec driver
@@ -435,9 +436,9 @@ func (h *qemuHandle) Signal(s os.Signal) error {
 
 func (h *qemuHandle) Kill() error {
 	// First, try sending a graceful shutdown command via the qemu monitor
-	err := h.sendQemuShutdown()
+	err := sendQemuShutdown(h.logger, h.monitorPath, h.userPid)
 
-	// If we couldn't send a graceful shutdown via the monitor socket, we'll
+	// If we did not send a graceful shutdown via the monitor socket, we'll
 	// issue an interrupt to the qemu process as a last resort
 	if err != nil {
 		if err := h.executor.ShutDown(); err != nil {
@@ -448,15 +449,15 @@ func (h *qemuHandle) Kill() error {
 		}
 	}
 
-	// At this point, we're waiting for the qemu process to exit. If we've
-	// attempted a graceful shutdown and the guest shuts down in time, doneChan
+	// If the qemu process exits before the kill timeout is reached, doneChan
 	// will close and we'll exit without an error. If it takes too long, the
 	// timer will fire and we'll attempt to kill the process.
 	select {
 	case <-h.doneCh:
 		return nil
 	case <-time.After(h.killTimeout):
-		h.logger.Printf("[DEBUG] driver.qemu: kill timeout exceeded for user process pid %d", h.userPid)
+		h.logger.Printf("[DEBUG] driver.qemu: kill timeout of %s exceeded for user process pid %d", h.killTimeout.String(), h.userPid)
+
 		if h.pluginClient.Exited() {
 			return nil
 		}
@@ -489,21 +490,24 @@ func (h *qemuHandle) run() {
 	close(h.waitCh)
 }
 
-func (h *qemuHandle) sendQemuShutdown() error {
+func sendQemuShutdown(logger *log.Logger, monitorPath string, userPid int) error {
 	var err error
-	if h.monitorPath == "" {
+	if monitorPath == "" {
+		logger.Printf("[DEBUG] driver.qemu: monitorPath not set; will not attempt graceful shutdown for user process pid %d", userPid)
 		err = errors.New("monitorPath not set")
 	} else {
-		monitorSocket, err := net.Dial("unix", h.monitorPath)
+		var monitorSocket net.Conn
+		monitorSocket, err = net.Dial("unix", monitorPath)
 		if err == nil {
 			defer monitorSocket.Close()
-			h.logger.Printf("[DEBUG] driver.qemu: sending graceful shutdown command to qemu monitor socket %q for user process pid %d", h.monitorPath, h.userPid)
+			logger.Printf("[DEBUG] driver.qemu: sending graceful shutdown command to qemu monitor socket %q for user process pid %d", monitorPath, userPid)
 			_, err = monitorSocket.Write([]byte(qemuGracefulShutdownMsg))
 			if err != nil {
-				h.logger.Printf("[WARN] driver.qemu: failed to send shutdown message %q to monitor socket %q for user process pid %d: %s", qemuGracefulShutdownMsg, h.monitorPath, h.userPid, err)
+				logger.Printf("[WARN] driver.qemu: failed to send shutdown message %q to monitor socket %q for user process pid %d: %s", qemuGracefulShutdownMsg, monitorPath, userPid, err)
 			}
+		} else {
+			logger.Printf("[WARN] driver.qemu: could not connect to qemu monitor %q for user process pid %d: %s", monitorPath, userPid, err)
 		}
-		h.logger.Printf("[WARN] driver.qemu: could not connect to qemu monitor %q for user process pid %d: %s", h.monitorPath, h.userPid, err)
 	}
 	return err
 }
diff --git a/client/driver/qemu_test.go b/client/driver/qemu_test.go
index 646fd3d71..f770734c7 100644
--- a/client/driver/qemu_test.go
+++ b/client/driver/qemu_test.go
@@ -2,10 +2,12 @@ package driver
 
 import (
 	"fmt"
+	"os"
 	"path/filepath"
 	"strings"
 	"syscall"
 	"testing"
+	"time"
 
 	"github.com/hashicorp/nomad/client/config"
 	"github.com/hashicorp/nomad/nomad/structs"
@@ -69,7 +71,7 @@ func TestQemuDriver_StartOpen_Wait(t *testing.T) {
 		Config: map[string]interface{}{
 			"image_path":        "linux-0.2.img",
 			"accelerator":       "tcg",
-			"graceful_shutdown": true,
+			"graceful_shutdown": false,
 			"port_map": []map[string]int{{
 				"main": 22,
 				"web":  8080,
@@ -129,6 +131,96 @@ func TestQemuDriver_StartOpen_Wait(t *testing.T) {
 	}
 }
 
+func TestQemuDriver_GracefulShutdown(t *testing.T) {
+	if !testutil.IsTravis() {
+		t.Parallel()
+	}
+	ctestutils.QemuCompatible(t)
+	task := &structs.Task{
+		Name:   "linux",
+		Driver: "qemu",
+		Config: map[string]interface{}{
+			"image_path":        "linux-0.2.img",
+			"accelerator":       "tcg",
+			"graceful_shutdown": true,
+			"port_map": []map[string]int{{
+				"main": 22,
+				"web":  8080,
+			}},
+			"args": []string{"-nodefconfig", "-nodefaults"},
+		},
+		// With the use of tcg acceleration, it's very unlikely a qemu instance
+		// will boot (and gracefully halt) in a reasonable amount of time, so
+		// this timeout is kept low to reduce test execution time
+		KillTimeout: time.Duration(1 * time.Second),
+		LogConfig: &structs.LogConfig{
+			MaxFiles:      10,
+			MaxFileSizeMB: 10,
+		},
+		Resources: &structs.Resources{
+			CPU:      500,
+			MemoryMB: 512,
+			Networks: []*structs.NetworkResource{
+				{
+					ReservedPorts: []structs.Port{{Label: "main", Value: 22000}, {Label: "web", Value: 80}},
+				},
+			},
+		},
+	}
+
+	ctx := testDriverContexts(t, task)
+	defer ctx.AllocDir.Destroy()
+	d := NewQemuDriver(ctx.DriverCtx)
+
+	dst := ctx.ExecCtx.TaskDir.Dir
+
+	copyFile("./test-resources/qemu/linux-0.2.img", filepath.Join(dst, "linux-0.2.img"), t)
+
+	if _, err := d.Prestart(ctx.ExecCtx, task); err != nil {
+		t.Fatalf("Prestart failed: %v", err)
+	}
+
+	resp, err := d.Start(ctx.ExecCtx, task)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+
+	// The monitor socket will not exist immediately, so we'll wait up to
+	// 5 seconds for it to become available.
+	monitorPath := fmt.Sprintf("%s/linux/%s", ctx.AllocDir.AllocDir, qemuMonitorSocketName)
+	monitorPathExists := false
+	for i := 0; i < 5; i++ {
+		if _, err := os.Stat(monitorPath); !os.IsNotExist(err) {
+			fmt.Printf("Monitor socket exists at %q\n", monitorPath)
+			monitorPathExists = true
+			break
+		}
+		time.Sleep(1 * time.Second)
+	}
+	if monitorPathExists == false {
+		t.Fatalf("monitor socket did not exist after waiting 5 seconds")
+	}
+
+	// userPid supplied in sendQemuShutdown calls is bogus (it's used only
+	// for log output)
+	if err := sendQemuShutdown(ctx.DriverCtx.logger, "", 0); err == nil {
+		t.Fatalf("sendQemuShutdown should return an error if monitorPath parameter is empty")
+	}
+
+	if err := sendQemuShutdown(ctx.DriverCtx.logger, "/path/that/does/not/exist", 0); err == nil {
+		t.Fatalf("sendQemuShutdown should return an error if file does not exist at monitorPath")
+	}
+
+	if err := sendQemuShutdown(ctx.DriverCtx.logger, monitorPath, 0); err != nil {
+		t.Fatalf("unexpected error from sendQemuShutdown: %s", err)
+	}
+
+	// Clean up
+	if err := resp.Handle.Kill(); err != nil {
+		fmt.Printf("\nError killing Qemu test: %s", err)
+	}
+}
+
 func TestQemuDriverUser(t *testing.T) {
 	if !testutil.IsTravis() {
 		t.Parallel()

From b1145705d30fcc7f76dccfffd23e4f166931de4e Mon Sep 17 00:00:00 2001
From: Matt Mercer <mgordonmercer+github@gmail.com>
Date: Wed, 1 Nov 2017 15:14:56 -0700
Subject: [PATCH 08/12] Use strings.Replace() instead of custom function

---
 client/driver/qemu_test.go | 14 +++-----------
 1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/client/driver/qemu_test.go b/client/driver/qemu_test.go
index f770734c7..0a7e86af3 100644
--- a/client/driver/qemu_test.go
+++ b/client/driver/qemu_test.go
@@ -16,14 +16,6 @@ import (
 	ctestutils "github.com/hashicorp/nomad/client/testutil"
 )
 
-func generateString(length int) string {
-	var newString string
-	for i := 0; i < length; i++ {
-		newString = newString + "x"
-	}
-	return string(newString)
-}
-
 // The fingerprinter test should always pass, even if QEMU is not installed.
 func TestQemuDriver_Fingerprint(t *testing.T) {
 	if !testutil.IsTravis() {
@@ -309,13 +301,13 @@ func TestQemuDriverUser(t *testing.T) {
 }
 
 func TestQemuDriverGetMonitorPath(t *testing.T) {
-	shortPath := generateString(10)
+	shortPath := strings.Repeat("x", 10)
 	_, err := getMonitorPath(shortPath, "0")
 	if err != nil {
 		t.Fatal("Should not have returned an error")
 	}
 
-	longPath := generateString(legacyMaxMonitorPathLen + 100)
+	longPath := strings.Repeat("x", legacyMaxMonitorPathLen+100)
 	_, err = getMonitorPath(longPath, "0")
 	if err == nil {
 		t.Fatal("Should have returned an error")
@@ -325,7 +317,7 @@ func TestQemuDriverGetMonitorPath(t *testing.T) {
 		t.Fatal("Should not have returned an error")
 	}
 
-	maxLengthPath := generateString(legacyMaxMonitorPathLen)
+	maxLengthPath := strings.Repeat("x", legacyMaxMonitorPathLen)
 	_, err = getMonitorPath(maxLengthPath, "0")
 	if err != nil {
 		t.Fatal("Should not have returned an error")

From 43256af5f32b7a86eff097ab15d148405d3a7f5d Mon Sep 17 00:00:00 2001
From: Matt Mercer <mgordonmercer+github@gmail.com>
Date: Wed, 1 Nov 2017 16:52:44 -0700
Subject: [PATCH 09/12] Qemu driver: clean up test logging; retry integration
 test for longer

---
 client/driver/qemu.go      |  8 +++-----
 client/driver/qemu_test.go | 20 ++++++++++++--------
 2 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/client/driver/qemu.go b/client/driver/qemu.go
index 5ad11b9f2..2cab2bfef 100644
--- a/client/driver/qemu.go
+++ b/client/driver/qemu.go
@@ -491,13 +491,11 @@ func (h *qemuHandle) run() {
 }
 
 func sendQemuShutdown(logger *log.Logger, monitorPath string, userPid int) error {
-	var err error
 	if monitorPath == "" {
 		logger.Printf("[DEBUG] driver.qemu: monitorPath not set; will not attempt graceful shutdown for user process pid %d", userPid)
-		err = errors.New("monitorPath not set")
+		return errors.New("monitorPath not set")
 	} else {
-		var monitorSocket net.Conn
-		monitorSocket, err = net.Dial("unix", monitorPath)
+		monitorSocket, err := net.Dial("unix", monitorPath)
 		if err == nil {
 			defer monitorSocket.Close()
 			logger.Printf("[DEBUG] driver.qemu: sending graceful shutdown command to qemu monitor socket %q for user process pid %d", monitorPath, userPid)
@@ -508,6 +506,6 @@ func sendQemuShutdown(logger *log.Logger, monitorPath string, userPid int) error
 		} else {
 			logger.Printf("[WARN] driver.qemu: could not connect to qemu monitor %q for user process pid %d: %s", monitorPath, userPid, err)
 		}
+		return err
 	}
-	return err
 }
diff --git a/client/driver/qemu_test.go b/client/driver/qemu_test.go
index 0a7e86af3..9a74ca48b 100644
--- a/client/driver/qemu_test.go
+++ b/client/driver/qemu_test.go
@@ -53,6 +53,7 @@ func TestQemuDriver_Fingerprint(t *testing.T) {
 }
 
 func TestQemuDriver_StartOpen_Wait(t *testing.T) {
+	logger := testLogger()
 	if !testutil.IsTravis() {
 		t.Parallel()
 	}
@@ -119,11 +120,12 @@ func TestQemuDriver_StartOpen_Wait(t *testing.T) {
 
 	// Clean up
 	if err := resp.Handle.Kill(); err != nil {
-		fmt.Printf("\nError killing Qemu test: %s", err)
+		logger.Printf("Error killing Qemu test: %s", err)
 	}
 }
 
 func TestQemuDriver_GracefulShutdown(t *testing.T) {
+	logger := testLogger()
 	if !testutil.IsTravis() {
 		t.Parallel()
 	}
@@ -181,16 +183,16 @@ func TestQemuDriver_GracefulShutdown(t *testing.T) {
 	// 5 seconds for it to become available.
 	monitorPath := fmt.Sprintf("%s/linux/%s", ctx.AllocDir.AllocDir, qemuMonitorSocketName)
 	monitorPathExists := false
-	for i := 0; i < 5; i++ {
+	for i := 0; i < 100; i++ {
 		if _, err := os.Stat(monitorPath); !os.IsNotExist(err) {
-			fmt.Printf("Monitor socket exists at %q\n", monitorPath)
+			logger.Printf("monitor socket exists at %q\n", monitorPath)
 			monitorPathExists = true
 			break
 		}
-		time.Sleep(1 * time.Second)
+		time.Sleep(200 * time.Millisecond)
 	}
 	if monitorPathExists == false {
-		t.Fatalf("monitor socket did not exist after waiting 5 seconds")
+		t.Fatalf("monitor socket did not exist after waiting 20 seconds")
 	}
 
 	// userPid supplied in sendQemuShutdown calls is bogus (it's used only
@@ -208,9 +210,11 @@ func TestQemuDriver_GracefulShutdown(t *testing.T) {
 	}
 
 	// Clean up
-	if err := resp.Handle.Kill(); err != nil {
-		fmt.Printf("\nError killing Qemu test: %s", err)
-	}
+	defer func() {
+		if err := resp.Handle.Kill(); err != nil {
+			logger.Printf("Error killing Qemu test: %s", err)
+		}
+	}()
 }
 
 func TestQemuDriverUser(t *testing.T) {

From 00f90323c246ada399b2463ecc67abf02720f8c6 Mon Sep 17 00:00:00 2001
From: Matt Mercer <mgordonmercer+github@gmail.com>
Date: Wed, 1 Nov 2017 17:37:43 -0700
Subject: [PATCH 10/12] Qemu driver: defer cleanup sooner

---
 client/driver/qemu_test.go | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/client/driver/qemu_test.go b/client/driver/qemu_test.go
index 9a74ca48b..98a5de2c0 100644
--- a/client/driver/qemu_test.go
+++ b/client/driver/qemu_test.go
@@ -179,6 +179,13 @@ func TestQemuDriver_GracefulShutdown(t *testing.T) {
 		t.Fatalf("err: %v", err)
 	}
 
+	// Clean up
+	defer func() {
+		if err := resp.Handle.Kill(); err != nil {
+			logger.Printf("Error killing Qemu test: %s", err)
+		}
+	}()
+
 	// The monitor socket will not exist immediately, so we'll wait up to
 	// 5 seconds for it to become available.
 	monitorPath := fmt.Sprintf("%s/linux/%s", ctx.AllocDir.AllocDir, qemuMonitorSocketName)
@@ -208,13 +215,6 @@ func TestQemuDriver_GracefulShutdown(t *testing.T) {
 	if err := sendQemuShutdown(ctx.DriverCtx.logger, monitorPath, 0); err != nil {
 		t.Fatalf("unexpected error from sendQemuShutdown: %s", err)
 	}
-
-	// Clean up
-	defer func() {
-		if err := resp.Handle.Kill(); err != nil {
-			logger.Printf("Error killing Qemu test: %s", err)
-		}
-	}()
 }
 
 func TestQemuDriverUser(t *testing.T) {

From cef9ba9770d9ddcd291f1baadc908f930633c65b Mon Sep 17 00:00:00 2001
From: Matt Mercer <mgordonmercer+github@gmail.com>
Date: Thu, 2 Nov 2017 17:37:49 -0700
Subject: [PATCH 11/12] Qemu driver: tweaks in response to PR feedback Remove
 attribute for long qemu monitor path; misc cleanup; update tests

---
 client/driver/qemu.go      | 100 +++++++++++++++++--------------
 client/driver/qemu_test.go | 120 +++++++++++++++++++++++++++++++++----
 2 files changed, 163 insertions(+), 57 deletions(-)

diff --git a/client/driver/qemu.go b/client/driver/qemu.go
index 2cab2bfef..f26de4b2a 100644
--- a/client/driver/qemu.go
+++ b/client/driver/qemu.go
@@ -29,18 +29,26 @@ import (
 
 var (
 	reQemuVersion = regexp.MustCompile(`version (\d[\.\d+]+)`)
+
+	// Prior to qemu 2.10.1, monitor socket paths are truncated to 108 bytes.
+	// We should consider this if driver.qemu.version is < 2.10.1 and the
+	// generated monitor path is too long.
+	//
+	// Relevant fix is here:
+	// https://github.com/qemu/qemu/commit/ad9579aaa16d5b385922d49edac2c96c79bcfb6
+	qemuVersionLongSocketPathFix = semver.New("2.10.1")
 )
 
 const (
 	// The key populated in Node Attributes to indicate presence of the Qemu driver
-	qemuDriverAttr                = "driver.qemu"
-	qemuDriverVersionAttr         = "driver.qemu.version"
-	qemuDriverLongMonitorPathAttr = "driver.qemu.longsocketpaths"
+	qemuDriverAttr        = "driver.qemu"
+	qemuDriverVersionAttr = "driver.qemu.version"
 	// Represents an ACPI shutdown request to the VM (emulates pressing a physical power button)
 	// Reference: https://en.wikibooks.org/wiki/QEMU/Monitor
 	qemuGracefulShutdownMsg = "system_powerdown\n"
-	legacyMaxMonitorPathLen = 108
 	qemuMonitorSocketName   = "qemu-monitor.sock"
+	// Maximum socket path length prior to qemu 2.10.1
+	qemuLegacyMaxMonitorPathLen = 108
 )
 
 // QemuDriver is a driver for running images via Qemu
@@ -75,11 +83,27 @@ type qemuHandle struct {
 	doneCh         chan struct{}
 }
 
-func getMonitorPath(dir string, longPathSupport string) (string, error) {
-	if len(dir) > legacyMaxMonitorPathLen && longPathSupport != "1" {
-		return "", fmt.Errorf("monitor path is too long")
+// getMonitorPath is used to determine whether a qemu monitor socket can be
+// safely created and accessed in the task directory by the version of qemu
+// present on the host. If it is safe to use, the socket's full path is
+// returned along with a nil error. Otherwise, an empty string is returned
+// along with a descriptive error.
+func (d *QemuDriver) getMonitorPath(dir string) (string, error) {
+	var longPathSupport bool
+	currentQemuVer := d.DriverContext.node.Attributes[qemuDriverVersionAttr]
+	currentQemuSemver := semver.New(currentQemuVer)
+	if currentQemuSemver.LessThan(*qemuVersionLongSocketPathFix) {
+		longPathSupport = false
+		d.logger.Printf("[DEBUG] driver.qemu: long socket paths are not available in this version of QEMU (%s)", currentQemuVer)
+	} else {
+		longPathSupport = true
+		d.logger.Printf("[DEBUG] driver.qemu: long socket paths available in this version of QEMU (%s)", currentQemuVer)
 	}
-	return fmt.Sprintf("%s/%s", dir, qemuMonitorSocketName), nil
+	fullSocketPath := fmt.Sprintf("%s/%s", dir, qemuMonitorSocketName)
+	if len(fullSocketPath) > qemuLegacyMaxMonitorPathLen && longPathSupport == false {
+		return "", fmt.Errorf("monitor path is too long for this version of qemu")
+	}
+	return fullSocketPath, nil
 }
 
 // NewQemuDriver is used to create a new exec driver
@@ -154,21 +178,6 @@ func (d *QemuDriver) Fingerprint(cfg *config.Config, node *structs.Node) (bool,
 	node.Attributes[qemuDriverAttr] = "1"
 	node.Attributes[qemuDriverVersionAttr] = currentQemuVersion
 
-	// Prior to qemu 2.10.1, monitor socket paths are truncated to 108 bytes.
-	// We should consider this if driver.qemu.version is < 2.10.1 and the
-	// generated monitor path is too long.
-	//
-	// Relevant fix is here:
-	// https://github.com/qemu/qemu/commit/ad9579aaa16d5b385922d49edac2c96c79bcfb6
-	currentQemuSemver := semver.New(currentQemuVersion)
-	fixedSocketPathLenVer := semver.New("2.10.1")
-	if currentQemuSemver.LessThan(*fixedSocketPathLenVer) {
-		node.Attributes[qemuDriverLongMonitorPathAttr] = "0"
-		d.logger.Printf("[DEBUG] driver.qemu: long socket paths are not available in this version of QEMU (%s)", currentQemuVersion)
-	} else {
-		d.logger.Printf("[DEBUG] driver.qemu: long socket paths available in this version of QEMU (%s)", currentQemuVersion)
-		node.Attributes[qemuDriverLongMonitorPathAttr] = "1"
-	}
 	return true, nil
 }
 
@@ -233,13 +242,13 @@ func (d *QemuDriver) Start(ctx *ExecContext, task *structs.Task) (*StartResponse
 	if d.driverConfig.GracefulShutdown {
 		// This socket will be used to manage the virtual machine (for example,
 		// to perform graceful shutdowns)
-		monitorPath, err = getMonitorPath(ctx.TaskDir.Dir, ctx.TaskEnv.NodeAttrs[qemuDriverLongMonitorPathAttr])
-		if err == nil {
-			d.logger.Printf("[DEBUG] driver.qemu: got monitor path OK: %s", monitorPath)
-			args = append(args, "-monitor", fmt.Sprintf("unix:%s,server,nowait", monitorPath))
-		} else {
-			d.logger.Printf("[WARN] driver.qemu: %s", err)
+		monitorPath, err := d.getMonitorPath(ctx.TaskDir.Dir)
+		if err != nil {
+			d.logger.Printf("[ERR] driver.qemu: could not get qemu monitor path - error: %s", err)
+			return nil, err
 		}
+		d.logger.Printf("[DEBUG] driver.qemu: got monitor path OK: %s", monitorPath)
+		args = append(args, "-monitor", fmt.Sprintf("unix:%s,server,nowait", monitorPath))
 	}
 
 	// Add pass through arguments to qemu executable. A user can specify
@@ -436,11 +445,9 @@ func (h *qemuHandle) Signal(s os.Signal) error {
 
 func (h *qemuHandle) Kill() error {
 	// First, try sending a graceful shutdown command via the qemu monitor
-	err := sendQemuShutdown(h.logger, h.monitorPath, h.userPid)
-
-	// If we did not send a graceful shutdown via the monitor socket, we'll
-	// issue an interrupt to the qemu process as a last resort
-	if err != nil {
+	if err := sendQemuShutdown(h.logger, h.monitorPath, h.userPid); err != nil {
+		h.logger.Printf("[DEBUG] driver.qemu: error sending graceful shutdown for user process pid %d: %s", h.userPid, err)
+		// Issue an interrupt to the qemu process as a last resort
 		if err := h.executor.ShutDown(); err != nil {
 			if h.pluginClient.Exited() {
 				return nil
@@ -490,22 +497,23 @@ func (h *qemuHandle) run() {
 	close(h.waitCh)
 }
 
+// sendQemuShutdown attempts to issue an ACPI power-off command via the qemu
+// monitor
 func sendQemuShutdown(logger *log.Logger, monitorPath string, userPid int) error {
 	if monitorPath == "" {
 		logger.Printf("[DEBUG] driver.qemu: monitorPath not set; will not attempt graceful shutdown for user process pid %d", userPid)
 		return errors.New("monitorPath not set")
-	} else {
-		monitorSocket, err := net.Dial("unix", monitorPath)
-		if err == nil {
-			defer monitorSocket.Close()
-			logger.Printf("[DEBUG] driver.qemu: sending graceful shutdown command to qemu monitor socket %q for user process pid %d", monitorPath, userPid)
-			_, err = monitorSocket.Write([]byte(qemuGracefulShutdownMsg))
-			if err != nil {
-				logger.Printf("[WARN] driver.qemu: failed to send shutdown message %q to monitor socket %q for user process pid %d: %s", qemuGracefulShutdownMsg, monitorPath, userPid, err)
-			}
-		} else {
-			logger.Printf("[WARN] driver.qemu: could not connect to qemu monitor %q for user process pid %d: %s", monitorPath, userPid, err)
-		}
+	}
+	monitorSocket, err := net.Dial("unix", monitorPath)
+	if err != nil {
+		logger.Printf("[WARN] driver.qemu: could not connect to qemu monitor %q for user process pid %d: %s", monitorPath, userPid, err)
 		return err
 	}
+	defer monitorSocket.Close()
+	logger.Printf("[DEBUG] driver.qemu: sending graceful shutdown command to qemu monitor socket %q for user process pid %d", monitorPath, userPid)
+	_, err = monitorSocket.Write([]byte(qemuGracefulShutdownMsg))
+	if err != nil {
+		logger.Printf("[WARN] driver.qemu: failed to send shutdown message %q to monitor socket %q for user process pid %d: %s", qemuGracefulShutdownMsg, monitorPath, userPid, err)
+	}
+	return err
 }
diff --git a/client/driver/qemu_test.go b/client/driver/qemu_test.go
index 98a5de2c0..b0978ec9c 100644
--- a/client/driver/qemu_test.go
+++ b/client/driver/qemu_test.go
@@ -47,9 +47,6 @@ func TestQemuDriver_Fingerprint(t *testing.T) {
 	if node.Attributes[qemuDriverVersionAttr] == "" {
 		t.Fatalf("Missing Qemu driver version")
 	}
-	if node.Attributes[qemuDriverLongMonitorPathAttr] == "" {
-		t.Fatalf("Missing Qemu long monitor socket path support flag")
-	}
 }
 
 func TestQemuDriver_StartOpen_Wait(t *testing.T) {
@@ -145,7 +142,7 @@ func TestQemuDriver_GracefulShutdown(t *testing.T) {
 		},
 		// With the use of tcg acceleration, it's very unlikely a qemu instance
 		// will boot (and gracefully halt) in a reasonable amount of time, so
-		// this timeout is kept low to reduce test execution time
+		// this timeout is kept low to reduce test execution time.
 		KillTimeout: time.Duration(1 * time.Second),
 		LogConfig: &structs.LogConfig{
 			MaxFiles:      10,
@@ -166,6 +163,14 @@ func TestQemuDriver_GracefulShutdown(t *testing.T) {
 	defer ctx.AllocDir.Destroy()
 	d := NewQemuDriver(ctx.DriverCtx)
 
+	apply, err := d.Fingerprint(&config.Config{}, ctx.DriverCtx.node)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	if !apply {
+		t.Fatalf("should apply")
+	}
+
 	dst := ctx.ExecCtx.TaskDir.Dir
 
 	copyFile("./test-resources/qemu/linux-0.2.img", filepath.Join(dst, "linux-0.2.img"), t)
@@ -304,25 +309,118 @@ func TestQemuDriverUser(t *testing.T) {
 	}
 }
 
-func TestQemuDriverGetMonitorPath(t *testing.T) {
+func TestQemuDriverGetMonitorPathOldQemu(t *testing.T) {
+	task := &structs.Task{
+		Name:   "linux",
+		Driver: "qemu",
+		Config: map[string]interface{}{
+			"image_path":        "linux-0.2.img",
+			"accelerator":       "tcg",
+			"graceful_shutdown": true,
+			"port_map": []map[string]int{{
+				"main": 22,
+				"web":  8080,
+			}},
+			"args": []string{"-nodefconfig", "-nodefaults"},
+		},
+		KillTimeout: time.Duration(1 * time.Second),
+		LogConfig: &structs.LogConfig{
+			MaxFiles:      10,
+			MaxFileSizeMB: 10,
+		},
+		Resources: &structs.Resources{
+			CPU:      500,
+			MemoryMB: 512,
+			Networks: []*structs.NetworkResource{
+				{
+					ReservedPorts: []structs.Port{{Label: "main", Value: 22000}, {Label: "web", Value: 80}},
+				},
+			},
+		},
+	}
+
+	ctx := testDriverContexts(t, task)
+	defer ctx.AllocDir.Destroy()
+
+	// Simulate an older version of qemu which does not support long monitor socket paths
+	ctx.DriverCtx.node.Attributes[qemuDriverVersionAttr] = "2.0.0"
+
+	d := &QemuDriver{DriverContext: *ctx.DriverCtx}
+
 	shortPath := strings.Repeat("x", 10)
-	_, err := getMonitorPath(shortPath, "0")
+	_, err := d.getMonitorPath(shortPath)
 	if err != nil {
 		t.Fatal("Should not have returned an error")
 	}
 
-	longPath := strings.Repeat("x", legacyMaxMonitorPathLen+100)
-	_, err = getMonitorPath(longPath, "0")
+	longPath := strings.Repeat("x", qemuLegacyMaxMonitorPathLen+100)
+	_, err = d.getMonitorPath(longPath)
 	if err == nil {
 		t.Fatal("Should have returned an error")
 	}
-	_, err = getMonitorPath(longPath, "1")
+
+	// Max length includes the '/' separator and socket name
+	maxLengthCount := qemuLegacyMaxMonitorPathLen - len(qemuMonitorSocketName) - 1
+	maxLengthLegacyPath := strings.Repeat("x", maxLengthCount)
+	_, err = d.getMonitorPath(maxLengthLegacyPath)
+	if err != nil {
+		t.Fatalf("Should not have returned an error: %s", err)
+	}
+}
+
+func TestQemuDriverGetMonitorPathNewQemu(t *testing.T) {
+	task := &structs.Task{
+		Name:   "linux",
+		Driver: "qemu",
+		Config: map[string]interface{}{
+			"image_path":        "linux-0.2.img",
+			"accelerator":       "tcg",
+			"graceful_shutdown": true,
+			"port_map": []map[string]int{{
+				"main": 22,
+				"web":  8080,
+			}},
+			"args": []string{"-nodefconfig", "-nodefaults"},
+		},
+		KillTimeout: time.Duration(1 * time.Second),
+		LogConfig: &structs.LogConfig{
+			MaxFiles:      10,
+			MaxFileSizeMB: 10,
+		},
+		Resources: &structs.Resources{
+			CPU:      500,
+			MemoryMB: 512,
+			Networks: []*structs.NetworkResource{
+				{
+					ReservedPorts: []structs.Port{{Label: "main", Value: 22000}, {Label: "web", Value: 80}},
+				},
+			},
+		},
+	}
+
+	ctx := testDriverContexts(t, task)
+	defer ctx.AllocDir.Destroy()
+
+	// Simulate a version of qemu which supports long monitor socket paths
+	ctx.DriverCtx.node.Attributes[qemuDriverVersionAttr] = "2.99.99"
+
+	d := &QemuDriver{DriverContext: *ctx.DriverCtx}
+
+	shortPath := strings.Repeat("x", 10)
+	_, err := d.getMonitorPath(shortPath)
 	if err != nil {
 		t.Fatal("Should not have returned an error")
 	}
 
-	maxLengthPath := strings.Repeat("x", legacyMaxMonitorPathLen)
-	_, err = getMonitorPath(maxLengthPath, "0")
+	longPath := strings.Repeat("x", qemuLegacyMaxMonitorPathLen+100)
+	_, err = d.getMonitorPath(longPath)
+	if err != nil {
+		t.Fatal("Should not have returned an error")
+	}
+
+	maxLengthCount := qemuLegacyMaxMonitorPathLen - len(qemuMonitorSocketName) - 1
+	maxLengthLegacyPath := strings.Repeat("x", maxLengthCount)
+	_, err = d.getMonitorPath(maxLengthLegacyPath)
 	if err != nil {
 		t.Fatal("Should not have returned an error")
 	}

From 11e28708751291d96c50b2df3ca9c6d2c0234705 Mon Sep 17 00:00:00 2001
From: Matt Mercer <mgordonmercer+github@gmail.com>
Date: Fri, 3 Nov 2017 14:45:09 -0700
Subject: [PATCH 12/12] Qemu driver: clean up logging; fail unsupported
 features on Windows

---
 client/driver/qemu.go | 27 +++++++++++++++++++++------
 1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/client/driver/qemu.go b/client/driver/qemu.go
index f26de4b2a..f256c829c 100644
--- a/client/driver/qemu.go
+++ b/client/driver/qemu.go
@@ -33,6 +33,7 @@ var (
 	// Prior to qemu 2.10.1, monitor socket paths are truncated to 108 bytes.
 	// We should consider this if driver.qemu.version is < 2.10.1 and the
 	// generated monitor path is too long.
+
 	//
 	// Relevant fix is here:
 	// https://github.com/qemu/qemu/commit/ad9579aaa16d5b385922d49edac2c96c79bcfb6
@@ -240,11 +241,14 @@ func (d *QemuDriver) Start(ctx *ExecContext, task *structs.Task) (*StartResponse
 
 	var monitorPath string
 	if d.driverConfig.GracefulShutdown {
+		if runtime.GOOS == "windows" {
+			return nil, errors.New("QEMU graceful shutdown is unsupported on the Windows platform")
+		}
 		// This socket will be used to manage the virtual machine (for example,
 		// to perform graceful shutdowns)
 		monitorPath, err := d.getMonitorPath(ctx.TaskDir.Dir)
 		if err != nil {
-			d.logger.Printf("[ERR] driver.qemu: could not get qemu monitor path - error: %s", err)
+			d.logger.Printf("[ERR] driver.qemu: could not get qemu monitor path: %s", err)
 			return nil, err
 		}
 		d.logger.Printf("[DEBUG] driver.qemu: got monitor path OK: %s", monitorPath)
@@ -292,6 +296,9 @@ func (d *QemuDriver) Start(ctx *ExecContext, task *structs.Task) (*StartResponse
 
 	// If using KVM, add optimization args
 	if accelerator == "kvm" {
+		if runtime.GOOS == "windows" {
+			return nil, errors.New("KVM accelerator is unsupported on the Windows platform")
+		}
 		args = append(args,
 			"-enable-kvm",
 			"-cpu", "host",
@@ -444,10 +451,19 @@ func (h *qemuHandle) Signal(s os.Signal) error {
 }
 
 func (h *qemuHandle) Kill() error {
-	// First, try sending a graceful shutdown command via the qemu monitor
-	if err := sendQemuShutdown(h.logger, h.monitorPath, h.userPid); err != nil {
-		h.logger.Printf("[DEBUG] driver.qemu: error sending graceful shutdown for user process pid %d: %s", h.userPid, err)
-		// Issue an interrupt to the qemu process as a last resort
+	gracefulShutdownSent := false
+	// Attempt a graceful shutdown only if it was configured in the job
+	if h.monitorPath != "" {
+		if err := sendQemuShutdown(h.logger, h.monitorPath, h.userPid); err == nil {
+			gracefulShutdownSent = true
+		} else {
+			h.logger.Printf("[DEBUG] driver.qemu: error sending graceful shutdown for user process pid %d: %s", h.userPid, err)
+		}
+	}
+
+	// If Nomad did not send a graceful shutdown signal, issue an interrupt to
+	// the qemu process as a last resort
+	if gracefulShutdownSent == false {
 		if err := h.executor.ShutDown(); err != nil {
 			if h.pluginClient.Exited() {
 				return nil
@@ -501,7 +517,6 @@ func (h *qemuHandle) run() {
 // monitor
 func sendQemuShutdown(logger *log.Logger, monitorPath string, userPid int) error {
 	if monitorPath == "" {
-		logger.Printf("[DEBUG] driver.qemu: monitorPath not set; will not attempt graceful shutdown for user process pid %d", userPid)
 		return errors.New("monitorPath not set")
 	}
 	monitorSocket, err := net.Dial("unix", monitorPath)