From 8ff88950b8ad25be7a969bd3dc25bc8c135073a0 Mon Sep 17 00:00:00 2001
From: Andy Pan <panjf2000@gmail.com>
Date: Sat, 19 May 2018 13:09:44 +0800
Subject: [PATCH] add codes for reusing workers

---
 pool.go   | 20 ++++++++++++--------
 worker.go |  2 +-
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/pool.go b/pool.go
index d943c84..873a8c6 100644
--- a/pool.go
+++ b/pool.go
@@ -13,7 +13,7 @@ type f func()
 
 type Pool struct {
 	capacity int32
-	free     int32
+	running  int32
 	tasks    chan f
 	workers  chan *Worker
 	destroy  chan sig
@@ -23,7 +23,6 @@ type Pool struct {
 func NewPool(size int) *Pool {
 	p := &Pool{
 		capacity: int32(size),
-		free:     int32(size),
 		tasks:    make(chan f, math.MaxInt32),
 		//workers:  &sync.Pool{New: func() interface{} { return &Worker{} }},
 		workers: make(chan *Worker, size),
@@ -58,11 +57,11 @@ func (p *Pool) Push(task f) error {
 	return nil
 }
 func (p *Pool) Running() int32 {
-	return atomic.LoadInt32(&p.capacity) - atomic.LoadInt32(&p.free)
+	return atomic.LoadInt32(&p.running)
 }
 
 func (p *Pool) Free() int32 {
-	return atomic.LoadInt32(&p.free)
+	return atomic.LoadInt32(&p.capacity) - atomic.LoadInt32(&p.running)
 }
 
 func (p *Pool) Cap() int32 {
@@ -91,15 +90,20 @@ func (p *Pool) newWorker() *Worker {
 		exit: make(chan sig),
 	}
 	worker.run()
-	atomic.AddInt32(&p.free, -1)
+	atomic.AddInt32(&p.running, 1)
 	return worker
 }
 
 func (p *Pool) getWorker() *Worker {
 	var worker *Worker
-	if p.reachLimit() || p.Free() > 0 {
-		worker = <-p.workers
+	if p.reachLimit() {
+		select {
+			case worker = <-p.workers:
+				return worker
+		default:
+			worker = p.newWorker()
+		}
 	}
-	worker = p.newWorker()
+	worker = <-p.workers
 	return worker
 }
diff --git a/worker.go b/worker.go
index 42b9df4..76e8248 100644
--- a/worker.go
+++ b/worker.go
@@ -15,7 +15,7 @@ func (w *Worker) run() {
 			case f := <-w.task:
 				f()
 				w.pool.workers <- w
-				atomic.AddInt32(&w.pool.free, 1)
+				atomic.AddInt32(&w.pool.running, -1)
 			case <-w.exit:
 				return
 			}