sized down concurrency package

concurrency/scale.go

@@ -35,3 +35,36 @@ func (ch *ConcurrencyHandler) ScaleUp() {
 		ch.logger.Info("Concurrency already at maximum level; cannot increase further", zap.Int("currentSize", currentSize))
 	}
 }
+
+// ResizeSemaphore adjusts the size of the semaphore used to control concurrency. This method creates a new
+// semaphore with the specified new size and closes the old semaphore to ensure that no further tokens can
+// be acquired from it. This approach helps manage the transition from the old concurrency level to the new one
+// without affecting ongoing operations significantly.
+//
+// Parameters:
+//   - newSize: The new size for the semaphore, representing the updated limit on concurrent requests.
+//
+// This function should be called from within synchronization contexts, such as AdjustConcurrency, to avoid
+// race conditions and ensure that changes to the semaphore are consistent with the observed metrics.
+func (ch *ConcurrencyHandler) ResizeSemaphore(newSize int) {
+	newSem := make(chan struct{}, newSize)
+
+	// Transfer tokens from the old semaphore to the new one.
+	for {
+		select {
+		case token := <-ch.sem:
+			select {
+			case newSem <- token:
+				// Token transferred to new semaphore.
+			default:
+				// New semaphore is full, put token back to the old one to allow ongoing operations to complete.
+				ch.sem <- token
+			}
+		default:
+			// No more tokens to transfer.
+			close(ch.sem)
+			ch.sem = newSem
+			return
+		}
+	}
+}