Port SingleConnPool fix to v6

go.mod

@@ -4,3 +4,5 @@ require (
 	github.com/onsi/ginkgo v1.8.0
 	github.com/onsi/gomega v1.5.0
 )
+
+go 1.13

internal/pool/bench_test.go

@@ -85,7 +85,7 @@ func BenchmarkPoolGetRemove(b *testing.B) {
 					if err != nil {
 						b.Fatal(err)
 					}
-					connPool.Remove(cn)
+					connPool.Remove(cn, nil)
 				}
 			})
 		})

internal/pool/pool.go

@@ -38,7 +38,7 @@ type Pooler interface {
 
 	Get() (*Conn, error)
 	Put(*Conn)
-	Remove(*Conn)
+	Remove(*Conn, error)
 
 	Len() int
 	IdleLen() int
@@ -289,7 +289,7 @@ func (p *ConnPool) popIdle() *Conn {
 
 func (p *ConnPool) Put(cn *Conn) {
 	if !cn.pooled {
-		p.Remove(cn)
+		p.Remove(cn, nil)
 		return
 	}
 
@@ -300,7 +300,7 @@ func (p *ConnPool) Put(cn *Conn) {
 	p.freeTurn()
 }
 
-func (p *ConnPool) Remove(cn *Conn) {
+func (p *ConnPool) Remove(cn *Conn, reason error) {
 	p.removeConn(cn)
 	p.freeTurn()
 	_ = p.closeConn(cn)

internal/pool/pool_single.go

@@ -1,53 +1,203 @@
 package pool
 
+import (
+	"fmt"
+	"sync/atomic"
+)
+
+const (
+	stateDefault = 0
+	stateInited  = 1
+	stateClosed  = 2
+)
+
+type BadConnError struct {
+	wrapped error
+}
+
+var _ error = (*BadConnError)(nil)
+
+func (e BadConnError) Error() string {
+	return "pg: Conn is in a bad state"
+}
+
+func (e BadConnError) Unwrap() error {
+	return e.wrapped
+}
+
 type SingleConnPool struct {
-	cn *Conn
+	pool  Pooler
+	level int32 // atomic
+
+	state uint32 // atomic
+	ch    chan *Conn
+
+	_badConnError atomic.Value
 }
 
 var _ Pooler = (*SingleConnPool)(nil)
 
-func NewSingleConnPool(cn *Conn) *SingleConnPool {
-	return &SingleConnPool{
-		cn: cn,
+func NewSingleConnPool(pool Pooler) *SingleConnPool {
+	p, ok := pool.(*SingleConnPool)
+	if !ok {
+		p = &SingleConnPool{
+			pool: pool,
+			ch:   make(chan *Conn, 1),
+		}
+	}
+	atomic.AddInt32(&p.level, 1)
+	return p
+}
+
+func (p *SingleConnPool) SetConn(cn *Conn) {
+	if atomic.CompareAndSwapUint32(&p.state, stateDefault, stateInited) {
+		p.ch <- cn
+	} else {
+		panic("not reached")
 	}
 }
 
 func (p *SingleConnPool) NewConn() (*Conn, error) {
-	panic("not implemented")
+	return p.pool.NewConn()
 }
 
-func (p *SingleConnPool) CloseConn(*Conn) error {
-	panic("not implemented")
+func (p *SingleConnPool) CloseConn(cn *Conn) error {
+	return p.pool.CloseConn(cn)
 }
 
 func (p *SingleConnPool) Get() (*Conn, error) {
-	return p.cn, nil
+	// In worst case this races with Close which is not a very common operation.
+	for i := 0; i < 1000; i++ {
+		switch atomic.LoadUint32(&p.state) {
+		case stateDefault:
+			cn, err := p.pool.Get()
+			if err != nil {
+				return nil, err
+			}
+			if atomic.CompareAndSwapUint32(&p.state, stateDefault, stateInited) {
+				return cn, nil
+			}
+			p.pool.Remove(cn, ErrClosed)
+		case stateInited:
+			if err := p.badConnError(); err != nil {
+				return nil, err
+			}
+			cn, ok := <-p.ch
+			if !ok {
+				return nil, ErrClosed
+			}
+			return cn, nil
+		case stateClosed:
+			return nil, ErrClosed
+		default:
+			panic("not reached")
+		}
+	}
+	return nil, fmt.Errorf("pg: SingleConnPool.Get: infinite loop")
 }
 
 func (p *SingleConnPool) Put(cn *Conn) {
-	if p.cn != cn {
-		panic("p.cn != cn")
+	defer func() {
+		if recover() != nil {
+			p.freeConn(cn)
+		}
+	}()
+	p.ch <- cn
+}
+
+func (p *SingleConnPool) freeConn(cn *Conn) {
+	if err := p.badConnError(); err != nil {
+		p.pool.Remove(cn, err)
+	} else {
+		p.pool.Put(cn)
 	}
 }
 
-func (p *SingleConnPool) Remove(cn *Conn) {
-	if p.cn != cn {
-		panic("p.cn != cn")
+func (p *SingleConnPool) Remove(cn *Conn, reason error) {
+	defer func() {
+		if recover() != nil {
+			p.pool.Remove(cn, ErrClosed)
 		}
+	}()
+	p._badConnError.Store(BadConnError{wrapped: reason})
+	p.ch <- cn
 }
 
 func (p *SingleConnPool) Len() int {
+	switch atomic.LoadUint32(&p.state) {
+	case stateDefault:
+		return 0
+	case stateInited:
 		return 1
+	case stateClosed:
+		return 0
+	default:
+		panic("not reached")
+	}
 }
 
 func (p *SingleConnPool) IdleLen() int {
-	return 0
+	return len(p.ch)
 }
 
 func (p *SingleConnPool) Stats() *Stats {
-	return nil
+	return &Stats{}
 }
 
 func (p *SingleConnPool) Close() error {
+	level := atomic.AddInt32(&p.level, -1)
+	if level > 0 {
+		return nil
+	}
+
+	for i := 0; i < 1000; i++ {
+		state := atomic.LoadUint32(&p.state)
+		if state == stateClosed {
+			return ErrClosed
+		}
+		if atomic.CompareAndSwapUint32(&p.state, state, stateClosed) {
+			close(p.ch)
+			cn, ok := <-p.ch
+			if ok {
+				p.freeConn(cn)
+			}
+			return nil
+		}
+	}
+
+	return fmt.Errorf("pg: SingleConnPool.Close: infinite loop")
+}
+
+func (p *SingleConnPool) Reset() error {
+	if p.badConnError() == nil {
+		return nil
+	}
+
+	select {
+	case cn, ok := <-p.ch:
+		if !ok {
+			return ErrClosed
+		}
+		p.pool.Remove(cn, ErrClosed)
+		p._badConnError.Store(BadConnError{wrapped: nil})
+	default:
+		return fmt.Errorf("pg: SingleConnPool does not have a Conn")
+	}
+
+	if !atomic.CompareAndSwapUint32(&p.state, stateInited, stateDefault) {
+		state := atomic.LoadUint32(&p.state)
+		return fmt.Errorf("pg: invalid SingleConnPool state: %d", state)
+	}
+
+	return nil
+}
+
+func (p *SingleConnPool) badConnError() error {
+	if v := p._badConnError.Load(); v != nil {
+		err := v.(BadConnError)
+		if err.wrapped != nil {
+			return err
+		}
+	}
 	return nil
 }

internal/pool/pool_sticky.go

@@ -55,13 +55,13 @@ func (p *StickyConnPool) putUpstream() {
 
 func (p *StickyConnPool) Put(cn *Conn) {}
 
-func (p *StickyConnPool) removeUpstream() {
-	p.pool.Remove(p.cn)
+func (p *StickyConnPool) removeUpstream(reason error) {
+	p.pool.Remove(p.cn, reason)
 	p.cn = nil
 }
 
-func (p *StickyConnPool) Remove(cn *Conn) {
-	p.removeUpstream()
+func (p *StickyConnPool) Remove(cn *Conn, reason error) {
+	p.removeUpstream(reason)
 }
 
 func (p *StickyConnPool) Len() int {
@@ -101,7 +101,7 @@ func (p *StickyConnPool) Close() error {
 		if p.reusable {
 			p.putUpstream()
 		} else {
-			p.removeUpstream()
+			p.removeUpstream(ErrClosed)
 		}
 	}
 

internal/pool/pool_test.go

@@ -63,7 +63,7 @@ var _ = Describe("ConnPool", func() {
 			// ok
 		}
 
-		connPool.Remove(cn)
+		connPool.Remove(cn, nil)
 
 		// Check that Get is unblocked.
 		select {
@@ -125,7 +125,7 @@ var _ = Describe("MinIdleConns", func() {
 
 			Context("after Remove", func() {
 				BeforeEach(func() {
-					connPool.Remove(cn)
+					connPool.Remove(cn, nil)
 				})
 
 				It("has idle connections", func() {
@@ -202,7 +202,7 @@ var _ = Describe("MinIdleConns", func() {
 				BeforeEach(func() {
 					perform(len(cns), func(i int) {
 						mu.RLock()
-						connPool.Remove(cns[i])
+						connPool.Remove(cns[i], nil)
 						mu.RUnlock()
 					})
 
@@ -350,7 +350,7 @@ var _ = Describe("conns reaper", func() {
 				Expect(connPool.Len()).To(Equal(4))
 				Expect(connPool.IdleLen()).To(Equal(0))
 
-				connPool.Remove(cn)
+				connPool.Remove(cn, nil)
 
 				Expect(connPool.Len()).To(Equal(3))
 				Expect(connPool.IdleLen()).To(Equal(0))
@@ -407,7 +407,7 @@ var _ = Describe("race", func() {
 				cn, err := connPool.Get()
 				Expect(err).NotTo(HaveOccurred())
 				if err == nil {
-					connPool.Remove(cn)
+					connPool.Remove(cn, nil)
 				}
 			}
 		})

internal/util.go

@@ -27,3 +27,13 @@ func isLower(s string) bool {
 	}
 	return true
 }
+
+func Unwrap(err error) error {
+	u, ok := err.(interface {
+		Unwrap() error
+	})
+	if !ok {
+		return nil
+	}
+	return u.Unwrap()
+}

redis.go

@@ -86,7 +86,10 @@ func (c *baseClient) _getConn() (*pool.Conn, error) {
 
 	err = c.initConn(cn)
 	if err != nil {
-		c.connPool.Remove(cn)
+		c.connPool.Remove(cn, err)
+		if err := internal.Unwrap(err); err != nil {
+			return nil, err
+		}
 		return nil, err
 	}
 
@@ -99,7 +102,7 @@ func (c *baseClient) releaseConn(cn *pool.Conn, err error) {
 	}
 
 	if internal.IsBadConn(err, false) {
-		c.connPool.Remove(cn)
+		c.connPool.Remove(cn, err)
 	} else {
 		c.connPool.Put(cn)
 	}
@@ -113,7 +116,7 @@ func (c *baseClient) releaseConnStrict(cn *pool.Conn, err error) {
 	if err == nil || internal.IsRedisError(err) {
 		c.connPool.Put(cn)
 	} else {
-		c.connPool.Remove(cn)
+		c.connPool.Remove(cn, err)
 	}
 }
 
@@ -541,10 +544,12 @@ type Conn struct {
 }
 
 func newConn(opt *Options, cn *pool.Conn) *Conn {
+	connPool := pool.NewSingleConnPool(nil)
+	connPool.SetConn(cn)
 	c := Conn{
 		baseClient: baseClient{
 			opt:      opt,
-			connPool: pool.NewSingleConnPool(cn),
+			connPool: connPool,
 		},
 	}
 	c.baseClient.init()