Add stress test and fix race it detected

pool.go

@@ -285,7 +285,9 @@ func (p *Pool) Acquire(ctx context.Context) (*Resource, error) {
 
 			select {
 			case <-ctx.Done():
+				p.cond.L.Lock()
 				p.canceledAcquireCount += 1
+				p.cond.L.Unlock()
 
 				// Allow goroutine waiting for signal to exit. Re-signal since we couldn't
 				// do anything with it. Another goroutine might be waiting.

pool_test.go

@@ -4,6 +4,8 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"math/rand"
+	"os"
 	"sync"
 	"testing"
 	"time"
@@ -478,6 +480,96 @@ func TestPoolAcquireReturnsErrorWhenPoolIsClosed(t *testing.T) {
 	assert.Nil(t, res)
 }
 
+func TestStress(t *testing.T) {
+	constructor, _ := createConstructor()
+	var destructorCalls Counter
+	destructor := func(interface{}) {
+		destructorCalls.Next()
+	}
+
+	pool := puddle.NewPool(constructor, destructor, 10)
+
+	finishChan := make(chan struct{})
+	wg := &sync.WaitGroup{}
+
+	releaseOrDestroyOrHijack := func(res *puddle.Resource) {
+		n := rand.Intn(100)
+		if n < 5 {
+			res.Hijack()
+			destructor(res)
+		} else if n < 10 {
+			res.Destroy()
+		} else {
+			res.Release()
+		}
+	}
+
+	actions := []func(){
+		// Acquire
+		func() {
+			res, err := pool.Acquire(context.Background())
+			if err != nil {
+				if err != puddle.ErrClosedPool {
+					assert.Failf(t, "stress acquire", "pool.Acquire returned unexpected err: %v", err)
+				}
+				return
+			}
+
+			time.Sleep(time.Duration(rand.Int63n(100)) * time.Millisecond)
+			releaseOrDestroyOrHijack(res)
+		},
+		// Acquire possibly canceled by context
+		func() {
+			ctx, cancel := context.WithTimeout(context.Background(), time.Duration(rand.Int63n(200))*time.Millisecond)
+			defer cancel()
+			res, err := pool.Acquire(ctx)
+			if err != nil {
+				if err != puddle.ErrClosedPool && err != context.Canceled && err != context.DeadlineExceeded {
+					assert.Failf(t, "stress acquire possibly canceled by context", "pool.Acquire returned unexpected err: %v", err)
+				}
+				return
+			}
+
+			time.Sleep(time.Duration(rand.Int63n(100)) * time.Millisecond)
+			releaseOrDestroyOrHijack(res)
+		},
+		// AcquireAllIdle (though under heavy load this will almost certainly always get an empty slice)
+		func() {
+			resources := pool.AcquireAllIdle()
+			for _, res := range resources {
+				res.Release()
+			}
+		},
+	}
+
+	for i := 0; i < 100; i++ {
+		wg.Add(1)
+		go func() {
+			for {
+				select {
+				case <-finishChan:
+					wg.Done()
+					return
+				default:
+				}
+
+				actions[rand.Intn(len(actions))]()
+			}
+		}()
+	}
+
+	s := os.Getenv("STRESS_TEST_DURATION")
+	if s == "" {
+		s = "1s"
+	}
+	testDuration, err := time.ParseDuration(s)
+	require.Nil(t, err)
+	time.AfterFunc(testDuration, func() { close(finishChan) })
+	wg.Wait()
+
+	pool.Close()
+}
+
 func BenchmarkPoolAcquireAndRelease(b *testing.B) {
 	benchmarks := []struct {
 		poolSize    int