⭐️ Randomize the start time of scanning in serve mode

apps/cnspec/cmd/backgroundjob/background.go

@@ -20,6 +20,9 @@ func New() (*BackgroundScanner, error) {
 type BackgroundScanner struct{}
 
 func (bs *BackgroundScanner) Run(runScanFn JobRunner) error {
- Serve(time.Duration(viper.GetInt64("timer"))*time.Minute, runScanFn)
+ Serve(
+ time.Duration(viper.GetInt64("timer"))*time.Minute,
+ time.Duration(viper.GetInt64("splay"))*time.Minute,
+ runScanFn)
  return nil
 }

apps/cnspec/cmd/backgroundjob/serve_unix.go

@@ -4,6 +4,7 @@
 package backgroundjob
 
 import (
+ "math/rand"
  "os"
  "os/signal"
  "sync"
@@ -13,19 +14,19 @@ import (
  "github.com/rs/zerolog/log"
 )
 
-func Serve(timer time.Duration, handler JobRunner) {
+func Serve(timer time.Duration, splay time.Duration, handler JobRunner) {
  log.Info().Msg("start cnspec background service")
- log.Info().Msgf("scan interval is %d minute(s)", int(timer.Minutes()))
+ log.Info().Msgf("scan interval is %d minute(s) with a splay of %d minutes(s)", int(timer.Minutes()), int(splay.Minutes()))
 
  quitChannel := make(chan os.Signal)
  signal.Notify(quitChannel, syscall.SIGINT, syscall.SIGTERM)
 
  shutdownChannel := make(chan struct{})
  waitGroup := &sync.WaitGroup{}
 
- initTick := time.Tick(1 * time.Second)
- defaultTick := time.Tick(timer)
- tick := initTick
+ t := time.NewTimer(time.Duration(rand.Int63n(int64(time.Minute))))
+ defer t.Stop()
+
  waitGroup.Add(1)
 
  go func(shutdownChannel chan struct{}, wg *sync.WaitGroup) {
@@ -40,14 +41,14 @@ func Serve(timer time.Duration, handler JobRunner) {
  }
 
  select {
- case <-tick:
- if tick == initTick {
- tick = defaultTick
- }
+ case <-t.C:
  err := handler()
  if err != nil {
  log.Error().Err(err).Send()
  }
+ nextRun := timer + time.Duration(rand.Int63n(int64(splay)))
+ log.Info().Msgf("next scan in %v", nextRun)
+ t.Reset(nextRun)
  case <-shutdownChannel:
  log.Info().Msg("stop worker")
  return

apps/cnspec/cmd/backgroundjob/serve_windows.go

@@ -42,9 +42,10 @@ type windowsService struct {
 func (m *windowsService) Execute(args []string, r <-chan svc.ChangeRequest, changes chan<- svc.Status) (ssec bool, errno uint32) {
  const cmdsAccepted = svc.AcceptStop | svc.AcceptShutdown
  changes <- svc.Status{State: svc.StartPending}
- initTick := time.Tick(1 * time.Second)
- defaulttick := time.Tick(m.Timer)
- tick := initTick
+
+ t := time.NewTimer(time.Duration(rand.Int63n(int64(time.Minute))))
+ defer t.Stop()
+
  log.Info().Msg("schedule background scan")
  changes <- svc.Status{State: svc.Running, Accepts: cmdsAccepted}
 
@@ -68,15 +69,15 @@ func (m *windowsService) Execute(args []string, r <-chan svc.ChangeRequest, chan
 loop:
  for {
  select {
- case <-tick:
- if tick == initTick {
- tick = defaulttick
- }
+ case <-t.C:
  select {
  case runChan <- struct{}{}:
  default:
  log.Error().Msg("scan not started. may be stuck")
  }
+ nextRun := timer + time.Duration(rand.Int63n(int64(splay)))
+ log.Info().Msgf("next scan in %v", nextRun)
+ t.Reset(nextRun)
  case c := <-r:
  switch c.Cmd {
  case svc.Interrogate:

apps/cnspec/cmd/serve.go

@@ -36,7 +36,9 @@ func init() {
  rootCmd.AddCommand(serveCmd)
  // background scan flags
  serveCmd.Flags().Int("timer", 60, "scan interval in minutes")
+ serveCmd.Flags().Int("splay", 60, "randomize the timer by up to this many minutes")
  serveCmd.Flags().MarkHidden("timer")
+ serveCmd.Flags().MarkHidden("splay")
  // set inventory
  serveCmd.Flags().String("inventory-file", "", "Set the path to the inventory file")
 }
@@ -47,6 +49,7 @@ var serveCmd = &cobra.Command{
 
  PreRun: func(cmd *cobra.Command, args []string) {
  viper.BindPFlag("timer", cmd.Flags().Lookup("timer"))
+ viper.BindPFlag("splay", cmd.Flags().Lookup("splay"))
  viper.BindPFlag("inventory-file", cmd.Flags().Lookup("inventory-file"))
  },
  Run: func(cmd *cobra.Command, args []string) {