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package main
import (
"log"
"os"
"path/filepath"
"time"
"unsafe"
"github.com/pkg/errors"
"github.com/sirupsen/logrus"
"github.com/urfave/cli"
"golang.org/x/sys/windows"
"golang.org/x/sys/windows/svc"
"golang.org/x/sys/windows/svc/mgr"
"google.golang.org/grpc"
)
const defaultServiceName = "buildkitd"
var (
serviceNameFlag string
registerServiceFlag bool
unregisterServiceFlag bool
logFileFlag string
kernel32 = windows.NewLazySystemDLL("kernel32.dll")
setStdHandle = kernel32.NewProc("SetStdHandle")
oldStderr windows.Handle
panicFile *os.File
)
// serviceFlags returns an array of flags for configuring buildkitd to run
// as a Windows service under control of SCM.
func serviceFlags() []cli.Flag {
return []cli.Flag{
cli.StringFlag{
Name: "service-name",
Usage: "Set the Windows service name",
Value: defaultServiceName,
},
cli.BoolFlag{
Name: "register-service",
Usage: "Register the service and exit",
},
cli.BoolFlag{
Name: "unregister-service",
Usage: "Unregister the service and exit",
},
cli.BoolFlag{
Name: "run-service",
Usage: "",
Hidden: true,
},
cli.StringFlag{
Name: "log-file",
Usage: "Path to the buildkitd log file",
},
}
}
func registerService() error {
p, err := os.Executable()
if err != nil {
return err
}
m, err := mgr.Connect()
if err != nil {
return err
}
defer m.Disconnect()
c := mgr.Config{
ServiceType: windows.SERVICE_WIN32_OWN_PROCESS,
StartType: mgr.StartAutomatic,
ErrorControl: mgr.ErrorNormal,
DisplayName: "Buildkitd",
Description: "Container image build engine",
}
// Configure the service to launch with the arguments that were just passed.
args := []string{"--run-service"}
for _, a := range os.Args[1:] {
if a != "--register-service" && a != "--unregister-service" {
args = append(args, a)
}
}
s, err := m.CreateService(serviceNameFlag, p, c, args...)
if err != nil {
return err
}
defer s.Close()
// See http://stackoverflow.com/questions/35151052/how-do-i-configure-failure-actions-of-a-windows-service-written-in-go
const (
scActionNone = 0
scActionRestart = 1
serviceConfigFailureActions = 2
)
type serviceFailureActions struct {
ResetPeriod uint32
RebootMsg *uint16
Command *uint16
ActionsCount uint32
Actions uintptr
}
type scAction struct {
Type uint32
Delay uint32
}
t := []scAction{
{Type: scActionRestart, Delay: uint32(15 * time.Second / time.Millisecond)},
{Type: scActionRestart, Delay: uint32(15 * time.Second / time.Millisecond)},
{Type: scActionNone},
}
lpInfo := serviceFailureActions{ResetPeriod: uint32(24 * time.Hour / time.Second), ActionsCount: uint32(3), Actions: uintptr(unsafe.Pointer(&t[0]))}
err = windows.ChangeServiceConfig2(s.Handle, serviceConfigFailureActions, (*byte)(unsafe.Pointer(&lpInfo)))
if err != nil {
return err
}
return nil
}
func unregisterService() error {
m, err := mgr.Connect()
if err != nil {
return err
}
defer m.Disconnect()
s, err := m.OpenService(serviceNameFlag)
if err != nil {
return err
}
defer s.Close()
err = s.Delete()
if err != nil {
return err
}
return nil
}
// applyPlatformFlags applies platform-specific flags.
func applyPlatformFlags(context *cli.Context) {
serviceNameFlag = context.GlobalString("service-name")
if serviceNameFlag == "" {
serviceNameFlag = defaultServiceName
}
for _, v := range []struct {
name string
d *bool
}{
{
name: "register-service",
d: ®isterServiceFlag,
},
{
name: "unregister-service",
d: &unregisterServiceFlag,
},
} {
*v.d = context.GlobalBool(v.name)
}
logFileFlag = context.GlobalString("log-file")
}
type handler struct {
fromsvc chan error
server *grpc.Server
}
// registerUnregisterService is an entrypoint early in the daemon startup
// to handle (un-)registering against Windows Service Control Manager (SCM).
// It returns an indication to stop on successful SCM operation, and an error.
func registerUnregisterService(root string) (bool, error) {
if unregisterServiceFlag {
if registerServiceFlag {
return true, errors.Errorf("--register-service and --unregister-service cannot be used together")
}
return true, unregisterService()
}
if registerServiceFlag {
return true, registerService()
}
isService, err := svc.IsWindowsService()
if err != nil {
return true, err
}
if isService {
if err := initPanicFile(filepath.Join(root, "panic.log")); err != nil {
return true, err
}
// The usual advice for Windows services is to either write to a log file or to the windows event
// log, the former of which we've exposed here via a --log-file flag. We additionally write panic
// stacks to a panic.log file to diagnose crashes. Below details the two different outcomes if
// --log-file is specified or not:
//
// --log-file is *not* specified.
// -------------------------------
// -logrus, the stdlibs logging package and os.Stderr output will go to
// NUL (Windows' /dev/null equivalent).
// -Panics will write their stack trace to the panic.log file.
// -Writing to the handle returned from GetStdHandle(STD_ERROR_HANDLE) will write
// to the panic.log file as the underlying handle itself has been redirected.
//
// --log-file *is* specified
// -------------------------------
// -Logging to logrus, the stdlibs logging package or directly to
// os.Stderr will all go to the log file specified.
// -Panics will write their stack trace to the panic.log file.
// -Writing to the handle returned from GetStdHandle(STD_ERROR_HANDLE) will write
// to the panic.log file as the underlying handle itself has been redirected.
var f *os.File
var err error
if logFileFlag != "" {
f, err = os.OpenFile(logFileFlag, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
if err != nil {
return true, errors.Wrapf(err, "open log file %q", logFileFlag)
}
} else {
// Windows services start with NULL stdio handles, and thus os.Stderr and friends will be
// backed by an os.File with a NULL handle. This means writes to os.Stderr will fail, which
// isn't a huge issue as we want output to be discarded if the user doesn't ask for the log
// file. However, writes succeeding but just going to the ether is a much better construct
// so use devnull instead of relying on writes failing. We use devnull instead of io.Discard
// as os.Stderr is an os.File and can't be assigned to io.Discard.
f, err = os.OpenFile(os.DevNull, os.O_WRONLY, 0)
if err != nil {
return true, err
}
}
// Reassign os.Stderr to the log file or NUL. Shim logs are copied to os.Stderr
// directly so this ensures those will end up in the log file as well if specified.
os.Stderr = f
// Assign the stdlibs log package in case of any miscellaneous uses by
// dependencies.
log.SetOutput(f)
logrus.SetOutput(f)
}
return false, nil
}
// launchService is the entry point for running the daemon under SCM.
func launchService(s *grpc.Server) error {
isService, err := svc.IsWindowsService()
if err != nil {
return err
}
if !isService {
return nil
}
h := &handler{
fromsvc: make(chan error),
server: s,
}
go func() {
h.fromsvc <- svc.Run(serviceNameFlag, h)
}()
// Wait for the first signal from the service handler.
err = <-h.fromsvc
if err != nil {
return err
}
return nil
}
// Execute implements the svc.Handler interface
func (h *handler) Execute(_ []string, r <-chan svc.ChangeRequest, s chan<- svc.Status) (bool, uint32) {
s <- svc.Status{State: svc.StartPending, Accepts: 0}
// Unblock launchService()
h.fromsvc <- nil
s <- svc.Status{State: svc.Running, Accepts: svc.AcceptStop | svc.AcceptShutdown}
Loop:
for c := range r {
switch c.Cmd {
case svc.Interrogate:
s <- c.CurrentStatus
case svc.Stop, svc.Shutdown:
s <- svc.Status{State: svc.StopPending, Accepts: 0}
// this should unblock serveGRPC() which will return control
// back to the main app, gracefully stopping everything else.
h.server.Stop()
break Loop
}
}
removePanicFile()
return false, 0
}
func initPanicFile(path string) error {
var err error
panicFile, err = os.OpenFile(path, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0644)
if err != nil {
return err
}
st, err := panicFile.Stat()
if err != nil {
return err
}
// If there are contents in the file already, move the file out of the way
// and replace it.
if st.Size() > 0 {
panicFile.Close()
os.Rename(path, path+".old")
panicFile, err = os.Create(path)
if err != nil {
return err
}
}
// Update STD_ERROR_HANDLE to point to the panic file so that Go writes to
// it when it panics. Remember the old stderr to restore it before removing
// the panic file.
sh := uint32(windows.STD_ERROR_HANDLE)
h, err := windows.GetStdHandle(sh)
if err != nil {
return err
}
oldStderr = h
r, _, err := setStdHandle.Call(uintptr(sh), panicFile.Fd())
if r == 0 && err != nil {
return err
}
return nil
}
func removePanicFile() {
if st, err := panicFile.Stat(); err == nil {
if st.Size() == 0 {
sh := uint32(windows.STD_ERROR_HANDLE)
setStdHandle.Call(uintptr(sh), uintptr(oldStderr))
panicFile.Close()
os.Remove(panicFile.Name())
}
}
}
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