feat: add rate limit to worker pool

pkg/fetcher.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"iter"
 	"sync"
+	"time"
 )
 
 // Fetcher is the concurrent manager
@@ -35,6 +36,23 @@ var StartPagination = Pagination{
 	Offset:  0,
 }
 
+func NewRateLimit(request_per int, time_scale time.Duration) <-chan time.Time {
+	rate_limit := make(chan time.Time, request_per)
+	tickrate := time_scale / time.Duration(request_per)
+
+	for range request_per {
+		rate_limit <- time.Now()
+	}
+
+	go func() {
+		for t := range time.Tick(tickrate) {
+			rate_limit <- t
+		}
+	}()
+
+	return rate_limit
+}
+
 // Work represents a function that processes a value of type S and returns a
 // result of type T or an error.
 type Work[T, S any] func(value T) (S, error)
@@ -47,6 +65,7 @@ type Worker[T, S any] struct {
 	transmiter chan<- S        // transmiter is the channel to which the worker sends results.
 	wg         *sync.WaitGroup // wg is the wait group to synchronize the completion of tasks.
 	work       Work[T, S]      // work is the function that processes tasks.
+	rate_limit <-chan time.Time
 }
 
 type WorkerManager[T, S any] struct {
@@ -87,7 +106,7 @@ func (manager *WorkerManager[T, S]) GetWorkUnit() iter.Seq[S] {
 
 	return func(yield func(S) bool) {
 		for {
-			// TODO: handle tiemouts and rate-limits
+			// TODO: handle tiemouts
 			select {
 			case value := <-manager.workers_transmiter:
 				if !yield(value) {
@@ -106,12 +125,19 @@ func spawn_worker[T, S any](worker *Worker[T, S]) {
 
 	// TODO: handle errors
 	for unit := range worker.receptor {
+		// Wait for rate-limit
+		<-worker.rate_limit
+
 		value, _ := worker.work(unit)
 		worker.transmiter <- value
 	}
 }
 
-func createWorkerPool[T, S any](max_workers uint8, work Work[T, S]) *WorkerManager[T, S] {
+func createWorkerPool[T, S any](
+	max_workers uint8,
+	rate_limit <-chan time.Time,
+	work Work[T, S],
+) *WorkerManager[T, S] {
 	channel_size := max_workers * 3
 
 	manager := &WorkerManager[T, S]{
@@ -125,6 +151,7 @@ func createWorkerPool[T, S any](max_workers uint8, work Work[T, S]) *WorkerManag
 			id:         uint8(i),
 			receptor:   manager.workers_receptor,
 			transmiter: manager.workers_transmiter,
+			rate_limit: rate_limit,
 			wg:         &manager.active_workers,
 			work:       work,
 		}