/
service.go
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/
service.go
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// Package service wraps all the complexity of writing daemons while enabling
// seamless integration with OS service management facilities.
package service // import "gopkg.in/hlandau/service.v2"
import (
"expvar"
"fmt"
"gopkg.in/hlandau/easyconfig.v1/cflag"
"gopkg.in/hlandau/service.v2/gsptcall"
"gopkg.in/hlandau/svcutils.v1/exepath"
"io"
"net/http"
_ "net/http/pprof" // register pprof handler for debug server
"os"
"os/signal"
"runtime/pprof"
"sync"
"syscall"
"time"
)
// Flags
var (
fg = cflag.NewGroup(nil, "service")
cpuProfileFlag = cflag.String(fg, "cpuprofile", "", "Write CPU profile to file")
debugServerAddrFlag = cflag.String(fg, "debugserveraddr", "", "Address for debug server to listen on (do not specify a public address) (default: disabled)")
)
type nullWriter struct{}
func (nw nullWriter) Write(p []byte) (n int, err error) {
return len(p), nil
}
func init() {
expvar.NewString("service.startTime").Set(time.Now().String())
}
// This function should typically be called directly from func main(). It takes
// care of all housekeeping for running services and handles service lifecycle.
func Main(info *Info) {
info.main()
}
// The interface between the service library and the application-specific code.
// The application calls the methods in the provided instance of this interface
// at various stages in its lifecycle.
type Manager interface {
// Must be called when the service is ready to drop privileges.
// This must be called before SetStarted().
DropPrivileges() error
// Must be called by a service payload when it has finished starting.
SetStarted()
// A service payload must stop when this channel is closed.
StopChan() <-chan struct{}
// Called by a service payload to provide a single line of information on the
// current status of that service.
SetStatus(status string)
}
// Used only by the NewFunc interface.
type Runnable interface {
// Start the runnable. Any initialization requiring root privileges must
// already have been obtained as this will be called after dropping
// privileges. Must return.
Start() error
// Stop the runnable. Must return.
Stop() error
}
// An upgrade interface for Runnable, implementation of which is optional.
type StatusSource interface {
// Return a channel on which status messages will be sent. If a Runnable
// implements this, it is guaranteed that the channel will be consumed until
// Stop is called.
StatusChan() <-chan string
}
// An instantiable service.
type Info struct {
// Recommended. Codename for the service, e.g. "foobar"
//
// If this is not set, exepath.ProgramName is used, which by default is the
// program's binary basename (e.g. "FooBar.exe" would become "foobar").
Name string
// Required unless NewFunc is specified instead. Starts the service. Must not
// return until the service has stopped. Must call smgr.SetStarted() to
// indicate when it has finished starting and use smgr.StopChan() to
// determine when to stop.
//
// Should call SetStatus() periodically with a status string.
RunFunc func(smgr Manager) error
// Optional. An alternative to RunFunc. If this is provided, RunFunc must not
// be specified, and this package will provide its own implementation of
// RunFunc.
//
// The NewFunc will be called to instantiate the runnable service.
// Privileges will then be dropped and Start will be called. Start must
// return. When the service is to be stopped, Stop will be called. Stop must
// return.
//
// To implement status notification, implement also the StatusSource interface.
NewFunc func() (Runnable, error)
Title string // Optional. Friendly name for the service, e.g. "Foobar Web Server"
Description string // Optional. Single line description for the service
AllowRoot bool // May the service run as root? If false, the service will refuse to run as root unless privilege dropping is set.
DefaultChroot string // Default path to chroot to. Use this if the service can be chrooted without consequence.
NoBanSuid bool // Set to true if the ability to execute suid binaries must be retained.
// Are we being started by systemd with [Service] Type=notify?
// If so, we can issue service status notifications to systemd.
systemd bool
// Path to created PID file.
pidFileName string
pidFile io.Closer
}
func (info *Info) main() {
err := info.maine()
if err != nil {
fmt.Fprintf(os.Stderr, "Error in service: %+v\n", err)
os.Exit(1)
}
}
func (info *Info) maine() error {
if info.Name == "" {
info.Name = exepath.ProgramName
} else if exepath.ProgramNameSetter == "default" {
exepath.ProgramName = info.Name
exepath.ProgramNameSetter = "service"
}
if info.Name == "" {
panic("service name must be specified")
}
if info.Title == "" {
info.Title = info.Name
}
if info.Description == "" {
info.Description = info.Title
}
err := info.commonPre()
if err != nil {
return err
}
err = info.setRunFunc()
if err != nil {
return err
}
// profiling
if cpuProfileFlag.Value() != "" {
f, err := os.Create(cpuProfileFlag.Value())
if err != nil {
return err
}
pprof.StartCPUProfile(f)
defer f.Close()
defer pprof.StopCPUProfile()
}
err = info.serviceMain()
return err
}
func (info *Info) commonPre() error {
if debugServerAddrFlag != nil && debugServerAddrFlag.Value() != "" {
go func() {
err := http.ListenAndServe(debugServerAddrFlag.Value(), nil)
if err != nil {
fmt.Fprintf(os.Stderr, "Couldn't start debug server: %+v\n", err)
}
}()
}
return nil
}
func (info *Info) setRunFunc() error {
if info.RunFunc != nil {
return nil
}
if info.NewFunc == nil {
panic("either RunFunc or NewFunc must be specified")
}
info.RunFunc = func(smgr Manager) error {
// instantiate runnable
r, err := info.NewFunc()
if err != nil {
return err
}
// setup status channel
getStatusChan := func() <-chan string {
return nil
}
if ss, ok := r.(StatusSource); ok {
getStatusChan = func() <-chan string {
return ss.StatusChan()
}
}
// drop privileges
err = smgr.DropPrivileges()
if err != nil {
return err
}
// start
err = r.Start()
if err != nil {
return err
}
//
smgr.SetStarted()
smgr.SetStatus(info.Name + ": running ok")
// wait for status messages or stop requests
loop:
for {
select {
case statusMsg := <-getStatusChan():
smgr.SetStatus(info.Name + ": " + statusMsg)
case <-smgr.StopChan():
break loop
}
}
// stop
return r.Stop()
}
return nil
}
type ihandler struct {
info *Info
stopChan chan struct{}
statusMutex sync.Mutex
statusNotifyChan chan struct{}
startedChan chan struct{}
status string
started bool
stopping bool
dropped bool
}
func (h *ihandler) SetStarted() {
if !h.dropped {
panic("service must call DropPrivileges before calling SetStarted")
}
select {
case h.startedChan <- struct{}{}:
default:
}
}
func (h *ihandler) StopChan() <-chan struct{} {
return h.stopChan
}
func (h *ihandler) SetStatus(status string) {
h.statusMutex.Lock()
h.status = status
h.statusMutex.Unlock()
select {
case <-h.statusNotifyChan:
default:
}
}
func (h *ihandler) updateStatus() {
// systemd
if h.info.systemd {
s := ""
if h.started {
s += "READY=1\n"
}
if h.status != "" {
s += "STATUS=" + h.status + "\n"
}
systemdUpdateStatus(s)
// ignore error
}
if h.status != "" {
gsptcall.SetProcTitle(h.status)
}
}
func (info *Info) runInteractively() error {
smgr := ihandler{
info: info,
stopChan: make(chan struct{}),
statusNotifyChan: make(chan struct{}, 1),
startedChan: make(chan struct{}, 1),
}
doneChan := make(chan error)
go func() {
err := info.RunFunc(&smgr)
doneChan <- err
}()
sig := make(chan os.Signal, 1)
signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM)
var exitErr error
loop:
for {
select {
case <-sig:
if !smgr.stopping {
smgr.stopping = true
close(smgr.stopChan)
smgr.updateStatus()
}
case <-smgr.startedChan:
if !smgr.started {
smgr.started = true
smgr.updateStatus()
}
case <-smgr.statusNotifyChan:
smgr.updateStatus()
case exitErr = <-doneChan:
break loop
}
}
return exitErr
}
// © 2015 Hugo Landau <hlandau@devever.net> ISC License