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qemu.go
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qemu.go
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package driver
import (
"fmt"
"os/exec"
"path/filepath"
"regexp"
"runtime"
"strings"
"time"
"github.com/hashicorp/nomad/client/allocdir"
"github.com/hashicorp/nomad/client/config"
"github.com/hashicorp/nomad/client/driver/executor"
cstructs "github.com/hashicorp/nomad/client/driver/structs"
"github.com/hashicorp/nomad/client/fingerprint"
"github.com/hashicorp/nomad/client/getter"
"github.com/hashicorp/nomad/nomad/structs"
"github.com/mitchellh/mapstructure"
)
var (
reQemuVersion = regexp.MustCompile(`version (\d[\.\d+]+)`)
)
// QemuDriver is a driver for running images via Qemu
// We attempt to chose sane defaults for now, with more configuration available
// planned in the future
type QemuDriver struct {
DriverContext
fingerprint.StaticFingerprinter
}
type QemuDriverConfig struct {
ArtifactSource string `mapstructure:"artifact_source"`
Checksum string `mapstructure:"checksum"`
Accelerator string `mapstructure:"accelerator"`
PortMap []map[string]int `mapstructure:"port_map"` // A map of host port labels and to guest ports.
}
// qemuHandle is returned from Start/Open as a handle to the PID
type qemuHandle struct {
cmd executor.Executor
waitCh chan *cstructs.WaitResult
doneCh chan struct{}
}
// NewQemuDriver is used to create a new exec driver
func NewQemuDriver(ctx *DriverContext) Driver {
return &QemuDriver{DriverContext: *ctx}
}
func (d *QemuDriver) Fingerprint(cfg *config.Config, node *structs.Node) (bool, error) {
bin := "qemu-system-x86_64"
if runtime.GOOS == "windows" {
// On windows, the "qemu-system-x86_64" command does not respond to the
// version flag.
bin = "qemu-img"
}
outBytes, err := exec.Command(bin, "--version").Output()
if err != nil {
return false, nil
}
out := strings.TrimSpace(string(outBytes))
matches := reQemuVersion.FindStringSubmatch(out)
if len(matches) != 2 {
return false, fmt.Errorf("Unable to parse Qemu version string: %#v", matches)
}
node.Attributes["driver.qemu"] = "1"
node.Attributes["driver.qemu.version"] = matches[1]
return true, nil
}
// Run an existing Qemu image. Start() will pull down an existing, valid Qemu
// image and save it to the Drivers Allocation Dir
func (d *QemuDriver) Start(ctx *ExecContext, task *structs.Task) (DriverHandle, error) {
var driverConfig QemuDriverConfig
if err := mapstructure.WeakDecode(task.Config, &driverConfig); err != nil {
return nil, err
}
if len(driverConfig.PortMap) > 1 {
return nil, fmt.Errorf("Only one port_map block is allowed in the qemu driver config")
}
// Get the image source
source, ok := task.Config["artifact_source"]
if !ok || source == "" {
return nil, fmt.Errorf("Missing source image Qemu driver")
}
// Qemu defaults to 128M of RAM for a given VM. Instead, we force users to
// supply a memory size in the tasks resources
if task.Resources == nil || task.Resources.MemoryMB == 0 {
return nil, fmt.Errorf("Missing required Task Resource: Memory")
}
// Get the tasks local directory.
taskDir, ok := ctx.AllocDir.TaskDirs[d.DriverContext.taskName]
if !ok {
return nil, fmt.Errorf("Could not find task directory for task: %v", d.DriverContext.taskName)
}
// Proceed to download an artifact to be executed.
vmPath, err := getter.GetArtifact(
filepath.Join(taskDir, allocdir.TaskLocal),
driverConfig.ArtifactSource,
driverConfig.Checksum,
d.logger,
)
if err != nil {
return nil, err
}
vmID := filepath.Base(vmPath)
// Parse configuration arguments
// Create the base arguments
accelerator := "tcg"
if driverConfig.Accelerator != "" {
accelerator = driverConfig.Accelerator
}
// TODO: Check a lower bounds, e.g. the default 128 of Qemu
mem := fmt.Sprintf("%dM", task.Resources.MemoryMB)
args := []string{
"qemu-system-x86_64",
"-machine", "type=pc,accel=" + accelerator,
"-name", vmID,
"-m", mem,
"-drive", "file=" + vmPath,
"-nodefconfig",
"-nodefaults",
"-nographic",
}
// Check the Resources required Networks to add port mappings. If no resources
// are required, we assume the VM is a purely compute job and does not require
// the outside world to be able to reach it. VMs ran without port mappings can
// still reach out to the world, but without port mappings it is effectively
// firewalled
protocols := []string{"udp", "tcp"}
if len(task.Resources.Networks) > 0 && len(driverConfig.PortMap) == 1 {
// Loop through the port map and construct the hostfwd string, to map
// reserved ports to the ports listenting in the VM
// Ex: hostfwd=tcp::22000-:22,hostfwd=tcp::80-:8080
var forwarding []string
taskPorts := task.Resources.Networks[0].MapLabelToValues(nil)
for label, guest := range driverConfig.PortMap[0] {
host, ok := taskPorts[label]
if !ok {
return nil, fmt.Errorf("Unknown port label %q", label)
}
for _, p := range protocols {
forwarding = append(forwarding, fmt.Sprintf("hostfwd=%s::%d-:%d", p, host, guest))
}
}
if len(forwarding) != 0 {
args = append(args,
"-netdev",
fmt.Sprintf("user,id=user.0%s", strings.Join(forwarding, ",")),
"-device", "virtio-net,netdev=user.0",
)
}
}
// If using KVM, add optimization args
if accelerator == "kvm" {
args = append(args,
"-enable-kvm",
"-cpu", "host",
// Do we have cores information available to the Driver?
// "-smp", fmt.Sprintf("%d", cores),
)
}
// Setup the command
cmd := executor.Command(args[0], args[1:]...)
if err := cmd.Limit(task.Resources); err != nil {
return nil, fmt.Errorf("failed to constrain resources: %s", err)
}
if err := cmd.ConfigureTaskDir(d.taskName, ctx.AllocDir); err != nil {
return nil, fmt.Errorf("failed to configure task directory: %v", err)
}
d.logger.Printf("[DEBUG] Starting QemuVM command: %q", strings.Join(args, " "))
if err := cmd.Start(); err != nil {
return nil, fmt.Errorf("failed to start command: %v", err)
}
d.logger.Printf("[INFO] Started new QemuVM: %s", vmID)
// Create and Return Handle
h := &qemuHandle{
cmd: cmd,
doneCh: make(chan struct{}),
waitCh: make(chan *cstructs.WaitResult, 1),
}
go h.run()
return h, nil
}
func (d *QemuDriver) Open(ctx *ExecContext, handleID string) (DriverHandle, error) {
// Find the process
cmd, err := executor.OpenId(handleID)
if err != nil {
return nil, fmt.Errorf("failed to open ID %v: %v", handleID, err)
}
// Return a driver handle
h := &execHandle{
cmd: cmd,
doneCh: make(chan struct{}),
waitCh: make(chan *cstructs.WaitResult, 1),
}
go h.run()
return h, nil
}
func (h *qemuHandle) ID() string {
id, _ := h.cmd.ID()
return id
}
func (h *qemuHandle) WaitCh() chan *cstructs.WaitResult {
return h.waitCh
}
func (h *qemuHandle) Update(task *structs.Task) error {
// Update is not possible
return nil
}
// TODO: allow a 'shutdown_command' that can be executed over a ssh connection
// to the VM
func (h *qemuHandle) Kill() error {
h.cmd.Shutdown()
select {
case <-h.doneCh:
return nil
case <-time.After(5 * time.Second):
return h.cmd.ForceStop()
}
}
func (h *qemuHandle) run() {
res := h.cmd.Wait()
close(h.doneCh)
h.waitCh <- res
close(h.waitCh)
}