[client] Add peer conn init limit (#3001)

Limit the peer connection initialization to 200 peers at the same time

util/semaphore-group/semaphore_group.go

@@ -0,0 +1,48 @@
+package semaphoregroup
+
+import (
+	"context"
+	"sync"
+)
+
+// SemaphoreGroup is a custom type that combines sync.WaitGroup and a semaphore.
+type SemaphoreGroup struct {
+	waitGroup sync.WaitGroup
+	semaphore chan struct{}
+}
+
+// NewSemaphoreGroup creates a new SemaphoreGroup with the specified semaphore limit.
+func NewSemaphoreGroup(limit int) *SemaphoreGroup {
+	return &SemaphoreGroup{
+		semaphore: make(chan struct{}, limit),
+	}
+}
+
+// Add increments the internal WaitGroup counter and acquires a semaphore slot.
+func (sg *SemaphoreGroup) Add(ctx context.Context) {
+	sg.waitGroup.Add(1)
+
+	// Acquire semaphore slot
+	select {
+	case <-ctx.Done():
+		return
+	case sg.semaphore <- struct{}{}:
+	}
+}
+
+// Done decrements the internal WaitGroup counter and releases a semaphore slot.
+func (sg *SemaphoreGroup) Done(ctx context.Context) {
+	sg.waitGroup.Done()
+
+	// Release semaphore slot
+	select {
+	case <-ctx.Done():
+		return
+	case <-sg.semaphore:
+	}
+}
+
+// Wait waits until the internal WaitGroup counter is zero.
+func (sg *SemaphoreGroup) Wait() {
+	sg.waitGroup.Wait()
+}