/
main.go
264 lines (217 loc) · 5.43 KB
/
main.go
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package main
import (
"flag"
"fmt"
"net/http"
"os"
"strings"
"time"
"golang.org/x/sys/windows/svc"
"golang.org/x/sys/windows/svc/debug"
"golang.org/x/sys/windows/svc/eventlog"
"golang.org/x/sys/windows/svc/mgr"
)
const serviceName = "winhchks"
const displayName = "winhchks"
const description = "This service makes a HTTP request to a URL every minute for a healthcheck."
const version = "v0.1.2"
type service struct {
elog debug.Log
url string
}
func main() {
var hchkURL string
flag.Usage = func() {
fmt.Fprintf(flag.CommandLine.Output(), "Usge of %s:\n", os.Args[0])
flag.PrintDefaults()
fmt.Fprintf(flag.CommandLine.Output(), " command\n \tCommand to run, one of: debug install remove start stop")
}
flag.StringVar(&hchkURL, "url", "", "Healthcheck URL, required with debug and install")
flag.Parse()
if inService, err := svc.IsWindowsService(); err != nil {
fmt.Fprintf(os.Stderr, "Failed to determine if we are running in service err='%v'", err)
os.Exit(1)
} else if inService {
runService(hchkURL, false)
return
}
if flag.NArg() == 0 {
flag.Usage()
os.Exit(1)
}
command := strings.ToLower(flag.Arg(0))
if (command == "debug" || command == "install") && hchkURL == "" {
flag.Usage()
os.Exit(1)
}
var err error
switch command {
case "debug":
runService(hchkURL, true)
return
case "install":
err = installService(hchkURL)
case "remove":
err = removeService()
case "start":
err = startService()
case "stop":
err = stopSerice()
default:
flag.Usage()
os.Exit(1)
}
if err != nil {
fmt.Fprintf(os.Stderr, "Failed to run command %s err='%v'", command, err)
os.Exit(1)
}
}
func calcNextRun() <-chan time.Time {
now := time.Now()
next := now.Add(time.Minute).Truncate(time.Minute).Add(2 * time.Second)
return time.After(next.Sub(now))
}
func installService(url string) error {
executable, err := os.Executable()
if err != nil {
return err
}
m, err := mgr.Connect()
if err != nil {
return err
}
defer m.Disconnect()
s, err := m.OpenService(serviceName)
if err == nil {
s.Close()
return fmt.Errorf("service is already installed")
}
s, err = m.CreateService(serviceName, executable, mgr.Config{
Description: description,
DisplayName: displayName,
StartType: mgr.StartAutomatic,
}, "-url", url)
if err != nil {
return err
}
defer s.Close()
if err = eventlog.InstallAsEventCreate(serviceName, eventlog.Error|eventlog.Info|eventlog.Warning); err != nil {
s.Delete()
return fmt.Errorf("eventlog install failed: %s", err)
}
return nil
}
func removeService() error {
m, err := mgr.Connect()
if err != nil {
return err
}
defer m.Disconnect()
s, err := m.OpenService(serviceName)
if err != nil {
return fmt.Errorf("service is not installed")
}
defer s.Close()
if err = s.Delete(); err != nil {
return err
}
if err = eventlog.Remove(serviceName); err != nil {
return fmt.Errorf("eventlog remove failed: %s", err)
}
return nil
}
func runService(url string, isDebug bool) {
var elog debug.Log
if isDebug {
elog = debug.New(serviceName)
} else {
elog, _ = eventlog.Open(serviceName)
}
defer elog.Close()
elog.Info(1, fmt.Sprintf("Starting service"))
run := svc.Run
if isDebug {
run = debug.Run
}
if err := run(serviceName, &service{elog: elog, url: url}); err != nil {
elog.Error(1, fmt.Sprintf("Service failed: %s", err))
} else {
elog.Info(1, fmt.Sprintf("Service stopped"))
}
}
func startService() error {
m, err := mgr.Connect()
if err != nil {
return err
}
defer m.Disconnect()
s, err := m.OpenService(serviceName)
if err != nil {
return fmt.Errorf("service is not installed")
}
defer s.Close()
if err = s.Start(); err != nil {
return fmt.Errorf("could not start service: %s", err)
}
return nil
}
func stopSerice() error {
m, err := mgr.Connect()
if err != nil {
return err
}
defer m.Disconnect()
s, err := m.OpenService(serviceName)
if err != nil {
return fmt.Errorf("service is not installed")
}
defer s.Close()
if _, err = s.Control(svc.Stop); err != nil {
return fmt.Errorf("could not stop service: %v", err)
}
return nil
}
func (s *service) Healthcheck() {
if resp, err := http.Get(s.url); err != nil {
s.elog.Error(1, fmt.Sprintf("Healthcheck err='%v'", err))
} else {
s.elog.Info(1, fmt.Sprintf("Healthcheck status='%s'", resp.Status))
resp.Body.Close()
}
}
func (s *service) Execute(args []string, r <-chan svc.ChangeRequest, changes chan<- svc.Status) (ssec bool, errno uint32) {
const cmdsAccepted = svc.AcceptStop | svc.AcceptShutdown | svc.AcceptPauseAndContinue
changes <- svc.Status{State: svc.StartPending}
paused := false
run := calcNextRun()
changes <- svc.Status{State: svc.Running, Accepts: cmdsAccepted}
s.elog.Info(1, fmt.Sprintf("Service started url='%s' version='%s'", s.url, version))
for {
select {
case <-run:
if !paused {
s.Healthcheck()
}
run = calcNextRun()
case c := <-r:
switch c.Cmd {
case svc.Continue:
paused = false
changes <- svc.Status{State: svc.Running, Accepts: cmdsAccepted}
s.elog.Info(1, fmt.Sprintf("Service resumed"))
case svc.Interrogate:
changes <- c.CurrentStatus
case svc.Pause:
paused = true
changes <- svc.Status{State: svc.Paused, Accepts: cmdsAccepted}
s.elog.Info(1, fmt.Sprintf("Service paused"))
case svc.Stop, svc.Shutdown:
changes <- svc.Status{State: svc.StopPending}
return
default:
s.elog.Error(1, fmt.Sprintf("Unexpected control request %+v", c))
}
}
}
return
}