refactor: refine the code in `retrieveWorker` to make it more readable (#295)

pool.go

@@ -333,31 +333,31 @@ func (p *Pool) addWaiting(delta int) {
 
 // retrieveWorker returns an available worker to run the tasks.
 func (p *Pool) retrieveWorker() (w worker) {
-	spawnWorker := func() {
+	p.lock.Lock()
+
+retry:
+	// First try to fetch the worker from the queue.
+	if w = p.workers.detach(); w != nil {
+		p.lock.Unlock()
+		return
+	}
+
+	// If the worker queue is empty and we don't run out of the pool capacity,
+	// then just spawn a new worker goroutine.
+	if capacity := p.Cap(); capacity == -1 || capacity > p.Running() {
+		p.lock.Unlock()
 		w = p.workerCache.Get().(*goWorker)
 		w.run()
-	}
-
-	p.lock.Lock()
-	w = p.workers.detach()
-	if w != nil { // first try to fetch the worker from the queue
-		p.lock.Unlock()
-	} else if capacity := p.Cap(); capacity == -1 || capacity > p.Running() {
-		// if the worker queue is empty and we don't run out of the pool capacity,
-		// then just spawn a new worker goroutine.
-		p.lock.Unlock()
-		spawnWorker()
-	} else { // otherwise, we'll have to keep them blocked and wait for at least one worker to be put back into pool.
-		if p.options.Nonblocking {
-			p.lock.Unlock()
 		return
 	}
-	retry:
+
-		if p.options.MaxBlockingTasks != 0 && p.Waiting() >= p.options.MaxBlockingTasks {
+	// Bail out early if it's in nonblocking mode or the number of pending callers reaches the maximum limit value.
+	if p.options.Nonblocking || (p.options.MaxBlockingTasks != 0 && p.Waiting() >= p.options.MaxBlockingTasks) {
 		p.lock.Unlock()
 		return
 	}
 
+	// Otherwise, we'll have to keep them blocked and wait for at least one worker to be put back into pool.
 	p.addWaiting(1)
 	p.cond.Wait() // block and wait for an available worker
 	p.addWaiting(-1)
@@ -367,17 +367,7 @@ func (p *Pool) retrieveWorker() (w worker) {
 		return
 	}
 
-		if w = p.workers.detach(); w == nil {
-			if p.Free() > 0 {
-				p.lock.Unlock()
-				spawnWorker()
-				return
-			}
 	goto retry
-		}
-		p.lock.Unlock()
-	}
-	return
 }
 
 // revertWorker puts a worker back into free pool, recycling the goroutines.

pool_func.go

@@ -339,31 +339,31 @@ func (p *PoolWithFunc) addWaiting(delta int) {
 
 // retrieveWorker returns an available worker to run the tasks.
 func (p *PoolWithFunc) retrieveWorker() (w worker) {
-	spawnWorker := func() {
+	p.lock.Lock()
+
+retry:
+	// First try to fetch the worker from the queue.
+	if w = p.workers.detach(); w != nil {
+		p.lock.Unlock()
+		return
+	}
+
+	// If the worker queue is empty and we don't run out of the pool capacity,
+	// then just spawn a new worker goroutine.
+	if capacity := p.Cap(); capacity == -1 || capacity > p.Running() {
+		p.lock.Unlock()
 		w = p.workerCache.Get().(*goWorkerWithFunc)
 		w.run()
-	}
-
-	p.lock.Lock()
-	w = p.workers.detach()
-	if w != nil { // first try to fetch the worker from the queue
-		p.lock.Unlock()
-	} else if capacity := p.Cap(); capacity == -1 || capacity > p.Running() {
-		// if the worker queue is empty and we don't run out of the pool capacity,
-		// then just spawn a new worker goroutine.
-		p.lock.Unlock()
-		spawnWorker()
-	} else { // otherwise, we'll have to keep them blocked and wait for at least one worker to be put back into pool.
-		if p.options.Nonblocking {
-			p.lock.Unlock()
 		return
 	}
-	retry:
+
-		if p.options.MaxBlockingTasks != 0 && p.Waiting() >= p.options.MaxBlockingTasks {
+	// Bail out early if it's in nonblocking mode or the number of pending callers reaches the maximum limit value.
+	if p.options.Nonblocking || (p.options.MaxBlockingTasks != 0 && p.Waiting() >= p.options.MaxBlockingTasks) {
 		p.lock.Unlock()
 		return
 	}
 
+	// Otherwise, we'll have to keep them blocked and wait for at least one worker to be put back into pool.
 	p.addWaiting(1)
 	p.cond.Wait() // block and wait for an available worker
 	p.addWaiting(-1)
@@ -373,17 +373,7 @@ func (p *PoolWithFunc) retrieveWorker() (w worker) {
 		return
 	}
 
-		if w = p.workers.detach(); w == nil {
-			if p.Free() > 0 {
-				p.lock.Unlock()
-				spawnWorker()
-				return
-			}
 	goto retry
-		}
-		p.lock.Unlock()
-	}
-	return
 }
 
 // revertWorker puts a worker back into free pool, recycling the goroutines.