fix issue #32, Get funciton would hang when all connections are closed

channel.go

@@ -3,7 +3,6 @@ package pool
 import (
 	"errors"
 	"fmt"
-	log "github.com/sirupsen/logrus"
 	"sync"
 	"time"
 	//"reflect"
@@ -47,13 +46,16 @@ type channelPool struct {
 	maxActive                int
 	openingConns             int
 	connReqs                 []chan connReq
+	openerCh                 chan struct{}
 }
 
 type idleConn struct {
 	conn interface{}
 	t    time.Time
 }
 
+var connectionRequestQueueSize = 1000000
+
 // NewChannelPool 初始化连接
 func NewChannelPool(poolConfig *Config) (Pool, error) {
 	if !(poolConfig.InitialCap <= poolConfig.MaxIdle && poolConfig.MaxCap >= poolConfig.MaxIdle && poolConfig.InitialCap >= 0) {
@@ -73,12 +75,15 @@ func NewChannelPool(poolConfig *Config) (Pool, error) {
 		idleTimeout:  poolConfig.IdleTimeout,
 		maxActive:    poolConfig.MaxCap,
 		openingConns: poolConfig.InitialCap,
+		openerCh:     make(chan struct{}, connectionRequestQueueSize),
 	}
 
 	if poolConfig.Ping != nil {
 		c.ping = poolConfig.Ping
 	}
 
+	go c.connectionOpener()
+
 	for i := 0; i < poolConfig.InitialCap; i++ {
 		conn, err := c.factory()
 		if err != nil {
@@ -99,6 +104,36 @@ func (c *channelPool) getConns() chan *idleConn {
 	return conns
 }
 
+// connectionOpener separate goroutine for opening new connection
+func (c *channelPool) connectionOpener() {
+	for {
+		select {
+		case _, ok := <-c.openerCh:
+			if !ok {
+				return
+			}
+			c.openNewConnection()
+		}
+	}
+}
+
+// openNewConnection Open one new connection
+func (c *channelPool) openNewConnection() {
+	conn, err := c.factory()
+	if err != nil {
+		c.mu.Lock()
+		c.openingConns--
+		c.maybeOpenNewConnections()
+		c.mu.Unlock()
+
+		// put nil connection into pool to wake up pending channel fetch
+		c.Put(nil)
+		return
+	}
+
+	c.Put(conn)
+}
+
 // Get 从pool中取一个连接
 func (c *channelPool) Get() (interface{}, error) {
 	conns := c.getConns()
@@ -129,7 +164,6 @@ func (c *channelPool) Get() (interface{}, error) {
 			return wrapConn.conn, nil
 		default:
 			c.mu.Lock()
-			log.Debugf("openConn %v %v", c.openingConns, c.maxActive)
 			if c.openingConns >= c.maxActive {
 				req := make(chan connReq, 1)
 				c.connReqs = append(c.connReqs, req)
@@ -138,6 +172,9 @@ func (c *channelPool) Get() (interface{}, error) {
 				if !ok {
 					return nil, ErrMaxActiveConnReached
 				}
+				if ret.idleConn.conn == nil {
+					return nil, errors.New("failed to create a new connection")
+				}
 				if timeout := c.idleTimeout; timeout > 0 {
 					if ret.idleConn.t.Add(timeout).Before(time.Now()) {
 						//丢弃并关闭该连接
@@ -151,27 +188,26 @@ func (c *channelPool) Get() (interface{}, error) {
 				c.mu.Unlock()
 				return nil, ErrClosed
 			}
+
+			// c.factory 耗时较长，采用乐观策略，先增加，失败后再减少
+			c.openingConns++
+			c.mu.Unlock()
 			conn, err := c.factory()
 			if err != nil {
+				c.mu.Lock()
+				c.openingConns--
 				c.mu.Unlock()
 				return nil, err
 			}
-			c.openingConns++
-			c.mu.Unlock()
 			return conn, nil
 		}
 	}
 }
 
 // Put 将连接放回pool中
 func (c *channelPool) Put(conn interface{}) error {
-	if conn == nil {
-		return errors.New("connection is nil. rejecting")
-	}
-
 	c.mu.Lock()
-
-	if c.conns == nil {
+	if c.conns == nil && conn != nil {
 		c.mu.Unlock()
 		return c.Close(conn)
 	}
@@ -180,12 +216,17 @@ func (c *channelPool) Put(conn interface{}) error {
 		req := c.connReqs[0]
 		copy(c.connReqs, c.connReqs[1:])
 		c.connReqs = c.connReqs[:l-1]
-		req <- connReq{
-			idleConn: &idleConn{conn: conn, t: time.Now()},
+		if conn == nil {
+			req <- connReq{idleConn: nil}
+			//return errors.New("connection is nil. rejecting")
+		} else {
+			req <- connReq{
+				idleConn: &idleConn{conn: conn, t: time.Now()},
+			}
 		}
 		c.mu.Unlock()
 		return nil
-	} else {
+	} else if conn != nil {
 		select {
 		case c.conns <- &idleConn{conn: conn, t: time.Now()}:
 			c.mu.Unlock()
@@ -196,20 +237,46 @@ func (c *channelPool) Put(conn interface{}) error {
 			return c.Close(conn)
 		}
 	}
+
+	c.mu.Unlock()
+	return errors.New("connection is nil, rejecting")
+}
+
+// maybeOpenNewConnections 如果有请求在，并且池里的连接上限未达到时，开启新的连接
+// Assumes c.mu is locked
+func (c *channelPool) maybeOpenNewConnections() {
+	numRequest := len(c.connReqs)
+
+	if c.maxActive > 0 {
+		numCanOpen := c.maxActive - c.openingConns
+		if numRequest > numCanOpen {
+			numRequest = numCanOpen
+		}
+	}
+	for numRequest > 0 {
+		c.openingConns++
+		numRequest--
+		c.openerCh <- struct{}{}
+	}
 }
 
 // Close 关闭单条连接
 func (c *channelPool) Close(conn interface{}) error {
 	if conn == nil {
 		return errors.New("connection is nil. rejecting")
 	}
-	c.mu.Lock()
-	defer c.mu.Unlock()
 	if c.close == nil {
 		return nil
 	}
+
+	var err error
+	err = c.close(conn)
+
+	c.mu.Lock()
 	c.openingConns--
-	return c.close(conn)
+	c.maybeOpenNewConnections()
+	c.mu.Unlock()
+	return err
 }
 
 // Ping 检查单条连接是否有效
@@ -229,13 +296,18 @@ func (c *channelPool) Release() {
 	c.ping = nil
 	closeFun := c.close
 	c.close = nil
+	openerCh := c.openerCh
+	c.openerCh = nil
 	c.mu.Unlock()
 
 	if conns == nil {
 		return
 	}
 
+	// close channels
 	close(conns)
+	close(openerCh)
+
 	for wrapConn := range conns {
 		//log.Printf("Type %v\n",reflect.TypeOf(wrapConn.conn))
 		closeFun(wrapConn.conn)

go.mod

@@ -2,4 +2,4 @@ module github.com/silenceper/pool
 
 go 1.13
 
-require github.com/sirupsen/logrus v1.4.2
+//require github.com/sirupsen/logrus v1.4.2