Add --worker-delay flag to rate-limit on startup

README.md

@@ -83,4 +83,6 @@ Usage of sequence:
         Timeout of the render request (default 1m0s)
   -width int
         The width of the image (default 1920)
+  -worker-delay duration
+        Delay worker startup (default 2s)
 ```

cmd/grafana-image-renderer-cli/main.go

@@ -57,6 +57,7 @@ func main() {
 		startPadding    = sequenceCommand.Duration("start-padding", 0, "Duration to add to the start of the frame")
 		endPadding      = sequenceCommand.Duration("end-padding", 0, "Duration to add to the end of the frame")
 		maxConcurrency  = sequenceCommand.Int("max-concurrency", 5, "Maximum number of concurrent render requests")
+		workerDelay     = sequenceCommand.Duration("worker-delay", 2*time.Second, "Delay worker startup")
 		outDirectory    = sequenceCommand.String("out-directory", "frames", "Directory to write rendered frames to")
 
 		imageCommand = flag.NewFlagSet("image", flag.ExitOnError)
@@ -160,6 +161,7 @@ func main() {
 			Interval:       *frameInterval,
 			StartPadding:   *startPadding,
 			EndPadding:     *endPadding,
+			WorkerDelay:    *workerDelay,
 			MaxConcurrency: *maxConcurrency,
 			SaveCallback: func(b []byte, n int) error {
 				filename := filepath.Join(*outDirectory, fmt.Sprintf("%06d.png", n))

pkg/sequencer/sequencer.go

@@ -6,7 +6,7 @@ import (
 )
 
 // RenderFunc is used to define render behavior. You should define the
-// call that should be made to the renderer. In its sumplest form, it
+// call that should be made to the renderer. In its simplest form, it
 // should simply call client.Render with the time parameters passed.
 type RenderFunc func(time.Time, time.Time) ([]byte, int, error)
 
@@ -35,6 +35,9 @@ type FrameSequencer struct {
 	// Padding can be added or subtracted from the frame.
 	StartPadding, EndPadding time.Duration
 
+	// Delay before starting each new worker.
+	WorkerDelay time.Duration
+
 	// Maximum number of concurrent render requests.
 	MaxConcurrency int
 
@@ -91,7 +94,8 @@ func (s *FrameSequencer) Sequence(start, end int) {
 	}
 }
 
-func (s *FrameSequencer) renderWorker(in <-chan frame, out chan<- error) {
+func (s *FrameSequencer) renderWorker(n int, in <-chan frame, out chan<- error) {
+	time.Sleep(s.WorkerDelay * time.Duration(n))
 	for f := range in {
 		startTime := time.Now()
 		fmt.Printf("Rendering frame %d\n", f.num)