From 204639c488901ffbff64c753bf4b9aa16c91c007 Mon Sep 17 00:00:00 2001
From: Daniel Hu <tao.hu@merico.dev>
Date: Mon, 11 Sep 2023 20:47:13 +0800
Subject: [PATCH] Fix cond issue and workerStack index order issue

---
 gopool.go                | 15 ++++++++++++++-
 gopool_benchmark_test.go |  2 +-
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/gopool.go b/gopool.go
index 0c356f7..0875445 100644
--- a/gopool.go
+++ b/gopool.go
@@ -2,6 +2,7 @@ package gopool
 
 import (
 	"context"
+	"sort"
 	"sync"
 	"time"
 )
@@ -153,26 +154,38 @@ func (p *goPool) adjustWorkers() {
 	ticker := time.NewTicker(p.adjustInterval)
 	defer ticker.Stop()
 
+	var adjustFlag bool
+
 	for {
+		adjustFlag = false
 		select {
 		case <-ticker.C:
 			p.cond.L.Lock()
 			if len(p.taskQueue) > len(p.workers)*3/4 && len(p.workers) < p.maxWorkers {
+				adjustFlag = true
 				// Double the number of workers until it reaches the maximum
 				newWorkers := min(len(p.workers)*2, p.maxWorkers) - len(p.workers)
 				for i := 0; i < newWorkers; i++ {
 					worker := newWorker()
 					p.workers = append(p.workers, worker)
+					// Don't use len(p.workerStack)-1 here, because it will be less than len(p.workers)-1 when the pool is busy
 					p.workerStack = append(p.workerStack, len(p.workers)-1)
 					worker.start(p, len(p.workers)-1)
 				}
-			} else if len(p.taskQueue) == 0 && len(p.workers) > p.minWorkers {
+			} else if len(p.taskQueue) == 0 && len(p.workerStack) == len(p.workers) && len(p.workers) > p.minWorkers {
+				adjustFlag = true
 				// Halve the number of workers until it reaches the minimum
 				removeWorkers := (len(p.workers) - p.minWorkers + 1) / 2
+				// Sort the workerStack before removing workers.
+				// [1,2,3,4,5] -working-> [1,2,3] -expansive-> [1,2,3,6,7] -idle-> [1,2,3,6,7,4,5]
+				sort.Ints(p.workerStack)
 				p.workers = p.workers[:len(p.workers)-removeWorkers]
 				p.workerStack = p.workerStack[:len(p.workerStack)-removeWorkers]
 			}
 			p.cond.L.Unlock()
+			if adjustFlag {
+				p.cond.Broadcast()
+			}
 		case <-p.ctx.Done():
 			return
 		}
diff --git a/gopool_benchmark_test.go b/gopool_benchmark_test.go
index 6790519..550c2f7 100644
--- a/gopool_benchmark_test.go
+++ b/gopool_benchmark_test.go
@@ -5,8 +5,8 @@ import (
 	"testing"
 	"time"
 
-	"github.com/daniel-hutao/spinlock"
 	"github.com/alitto/pond"
+	"github.com/daniel-hutao/spinlock"
 	"github.com/panjf2000/ants/v2"
 )