pool: rate limit number of open connections.

multi.go

@@ -24,7 +24,9 @@ func (c *Client) Multi() *Multi {
 }
 
 func (c *Multi) Close() error {
-	c.Unwatch()
+	if err := c.Unwatch().Err(); err != nil {
+		return err
+	}
 	return c.Client.Close()
 }
 

pool.go

@@ -12,7 +12,8 @@ import (
 )
 
 var (
-	errClosed = errors.New("redis: client is closed")
+	errClosed      = errors.New("redis: client is closed")
+	errRateLimited = errors.New("redis: you open connections too fast")
 )
 
 var (
@@ -83,7 +84,8 @@ func (cn *conn) Close() error {
 //------------------------------------------------------------------------------
 
 type connPool struct {
-	New func() (*conn, error)
+	dial func() (*conn, error)
+	rl   *rateLimiter
 
 	cond  *sync.Cond
 	conns *list.List
@@ -101,7 +103,8 @@ func newConnPool(
 	idleTimeout time.Duration,
 ) *connPool {
 	return &connPool{
-		New: dial,
+		dial: dial,
+		rl:   newRateLimiter(time.Second, 2*maxSize),
 
 		cond:  sync.NewCond(&sync.Mutex{}),
 		conns: list.New(),
@@ -111,6 +114,15 @@ func newConnPool(
 	}
 }
 
+func (p *connPool) new() (*conn, error) {
+	select {
+	case <-p.rl.C:
+	default:
+		return nil, errRateLimited
+	}
+	return p.dial()
+}
+
 func (p *connPool) Get() (*conn, bool, error) {
 	p.cond.L.Lock()
 
@@ -152,7 +164,7 @@ func (p *connPool) Get() (*conn, bool, error) {
 	}
 
 	if p.conns.Len() < p.maxSize {
-		cn, err := p.New()
+		cn, err := p.new()
 		if err != nil {
 			p.cond.L.Unlock()
 			return nil, false, err

rate_limit.go

@@ -0,0 +1,30 @@
+package redis
+
+import (
+	"time"
+)
+
+type rateLimiter struct {
+	C chan struct{}
+}
+
+func newRateLimiter(limit time.Duration, chanSize int) *rateLimiter {
+	rl := &rateLimiter{
+		C: make(chan struct{}, chanSize),
+	}
+	for i := 0; i < chanSize; i++ {
+		rl.C <- struct{}{}
+	}
+	go rl.loop(limit)
+	return rl
+}
+
+func (rl *rateLimiter) loop(limit time.Duration) {
+	for {
+		select {
+		case rl.C <- struct{}{}:
+		default:
+		}
+		time.Sleep(limit)
+	}
+}

redis_test.go

@@ -239,16 +239,16 @@ func (t *RedisConnPoolTest) TestConnPoolMaxSizeOnMultiClient(c *C) {
 }
 
 func (t *RedisConnPoolTest) TestConnPoolMaxSizeOnPubSub(c *C) {
-	const N = 1000
+	const N = 10
 
 	wg := &sync.WaitGroup{}
 	wg.Add(N)
 	for i := 0; i < N; i++ {
 		go func() {
+			defer wg.Done()
 			pubsub := t.client.PubSub()
 			c.Assert(pubsub.Subscribe(), IsNil)
 			c.Assert(pubsub.Close(), IsNil)
-			wg.Done()
 		}()
 	}
 	wg.Wait()
@@ -296,21 +296,11 @@ var _ = Suite(&RedisTest{})
 
 func Test(t *testing.T) { TestingT(t) }
 
-func (t *RedisTest) SetUpSuite(c *C) {
+func (t *RedisTest) SetUpTest(c *C) {
 	t.client = redis.NewTCPClient(&redis.Options{
 		Addr: ":6379",
 	})
-}
 
-func (t *RedisTest) TearDownSuite(c *C) {
-	c.Assert(t.client.Close(), IsNil)
-}
-
-func (t *RedisTest) SetUpTest(c *C) {
-	t.resetRedis(c)
-}
-
-func (t *RedisTest) resetRedis(c *C) {
 	// This is much faster than Flushall.
 	c.Assert(t.client.Select(1).Err(), IsNil)
 	c.Assert(t.client.FlushDb().Err(), IsNil)
@@ -318,6 +308,10 @@ func (t *RedisTest) resetRedis(c *C) {
 	c.Assert(t.client.FlushDb().Err(), IsNil)
 }
 
+func (t *RedisTest) TearDownTest(c *C) {
+	c.Assert(t.client.Close(), IsNil)
+}
+
 //------------------------------------------------------------------------------
 
 func (t *RedisTest) TestCmdStringMethod(c *C) {
@@ -2787,14 +2781,17 @@ func (t *RedisTest) transactionalIncr(c *C) ([]redis.Cmder, error) {
 }
 
 func (t *RedisTest) TestWatchUnwatch(c *C) {
+	const N = 10000
+
 	set := t.client.Set("key", "0")
 	c.Assert(set.Err(), IsNil)
 	c.Assert(set.Val(), Equals, "OK")
 
 	wg := &sync.WaitGroup{}
-	for i := 0; i < 1000; i++ {
+	for i := 0; i < N; i++ {
 		wg.Add(1)
 		go func() {
+			defer wg.Done()
 			for {
 				cmds, err := t.transactionalIncr(c)
 				if err == redis.TxFailedErr {
@@ -2805,14 +2802,13 @@ func (t *RedisTest) TestWatchUnwatch(c *C) {
 				c.Assert(cmds[0].Err(), IsNil)
 				break
 			}
-			wg.Done()
 		}()
 	}
 	wg.Wait()
 
 	get := t.client.Get("key")
 	c.Assert(get.Err(), IsNil)
-	c.Assert(get.Val(), Equals, "1000")
+	c.Assert(get.Val(), Equals, strconv.FormatInt(N, 10))
 }
 
 //------------------------------------------------------------------------------