Add auto-retry and MaxRetries option. Fixes #84.

Author: vmihailenco

command.go

@@ -47,6 +47,12 @@ func setCmdsErr(cmds []Cmder, e error) {
 	}
 }
 
+func resetCmds(cmds []Cmder) {
+	for _, cmd := range cmds {
+		cmd.reset()
+	}
+}
+
 func cmdString(cmd Cmder, val interface{}) string {
 	s := strings.Join(cmd.args(), " ")
 	if err := cmd.Err(); err != nil {

conn.go

@@ -7,14 +7,18 @@ import (
 	"gopkg.in/bufio.v1"
 )
 
+var (
+	zeroTime = time.Time{}
+)
+
 type conn struct {
 	netcn net.Conn
 	rd    *bufio.Reader
 	buf   []byte
 
 	usedAt       time.Time
-	readTimeout  time.Duration
-	writeTimeout time.Duration
+	ReadTimeout  time.Duration
+	WriteTimeout time.Duration
 }
 
 func newConnDialer(opt *options) func() (*conn, error) {
@@ -70,17 +74,17 @@ func (cn *conn) writeCmds(cmds ...Cmder) error {
 }
 
 func (cn *conn) Read(b []byte) (int, error) {
-	if cn.readTimeout != 0 {
-		cn.netcn.SetReadDeadline(time.Now().Add(cn.readTimeout))
+	if cn.ReadTimeout != 0 {
+		cn.netcn.SetReadDeadline(time.Now().Add(cn.ReadTimeout))
 	} else {
 		cn.netcn.SetReadDeadline(zeroTime)
 	}
 	return cn.netcn.Read(b)
 }
 
 func (cn *conn) Write(b []byte) (int, error) {
-	if cn.writeTimeout != 0 {
-		cn.netcn.SetWriteDeadline(time.Now().Add(cn.writeTimeout))
+	if cn.WriteTimeout != 0 {
+		cn.netcn.SetWriteDeadline(time.Now().Add(cn.WriteTimeout))
 	} else {
 		cn.netcn.SetWriteDeadline(zeroTime)
 	}

error.go

@@ -26,7 +26,7 @@ func (err redisError) Error() string {
 }
 
 func isNetworkError(err error) bool {
-	if _, ok := err.(*net.OpError); ok || err == io.EOF {
+	if _, ok := err.(net.Error); ok || err == io.EOF {
 		return true
 	}
 	return false
@@ -53,3 +53,11 @@ func isMovedError(err error) (moved bool, ask bool, addr string) {
 
 	return
 }
+
+// shouldRetry reports whether failed command should be retried.
+func shouldRetry(err error) bool {
+	if err == nil {
+		return false
+	}
+	return isNetworkError(err)
+}

export_test.go

@@ -1,9 +1,15 @@
 package redis
 
+import "net"
+
 func (c *baseClient) Pool() pool {
 	return c.connPool
 }
 
+func (cn *conn) SetNetConn(netcn net.Conn) {
+	cn.netcn = netcn
+}
+
 func HashSlot(key string) int {
 	return hashSlot(key)
 }

pipeline.go

@@ -50,26 +50,38 @@ func (c *Pipeline) Discard() error {
 
 // Exec always returns list of commands and error of the first failed
 // command if any.
-func (c *Pipeline) Exec() ([]Cmder, error) {
+func (c *Pipeline) Exec() (cmds []Cmder, retErr error) {
 	if c.closed {
 		return nil, errClosed
 	}
 	if len(c.cmds) == 0 {
-		return []Cmder{}, nil
+		return c.cmds, nil
 	}
 
-	cmds := c.cmds
+	cmds = c.cmds
 	c.cmds = make([]Cmder, 0, 0)
 
-	cn, err := c.client.conn()
-	if err != nil {
-		setCmdsErr(cmds, err)
-		return cmds, err
+	for i := 0; i <= c.client.opt.MaxRetries; i++ {
+		if i > 0 {
+			resetCmds(cmds)
+		}
+
+		cn, err := c.client.conn()
+		if err != nil {
+			setCmdsErr(cmds, err)
+			return cmds, err
+		}
+
+		retErr = c.execCmds(cn, cmds)
+		c.client.putConn(cn, err)
+		if shouldRetry(err) {
+			continue
+		}
+
+		break
 	}
 
-	err = c.execCmds(cn, cmds)
-	c.client.putConn(cn, err)
-	return cmds, err
+	return cmds, retErr
 }
 
 func (c *Pipeline) execCmds(cn *conn, cmds []Cmder) error {
@@ -79,17 +91,11 @@ func (c *Pipeline) execCmds(cn *conn, cmds []Cmder) error {
 	}
 
 	var firstCmdErr error
-	for i, cmd := range cmds {
+	for _, cmd := range cmds {
 		err := cmd.parseReply(cn.rd)
-		if err == nil {
-			continue
-		}
-		if firstCmdErr == nil {
+		if err != nil && firstCmdErr == nil {
 			firstCmdErr = err
 		}
-		if isNetworkError(err) {
-			setCmdsErr(cmds[i:], err)
-		}
 	}
 
 	return firstCmdErr

pool.go

@@ -16,10 +16,6 @@ var (
 	errPoolTimeout = errors.New("redis: connection pool timeout")
 )
 
-var (
-	zeroTime = time.Time{}
-)
-
 type pool interface {
 	First() *conn
 	Get() (*conn, error)

pubsub.go

@@ -63,7 +63,7 @@ func (c *PubSub) ReceiveTimeout(timeout time.Duration) (interface{}, error) {
 	if err != nil {
 		return nil, err
 	}
-	cn.readTimeout = timeout
+	cn.ReadTimeout = timeout
 
 	cmd := NewSliceCmd()
 	if err := cmd.parseReply(cn.rd); err != nil {
@@ -92,6 +92,7 @@ func (c *PubSub) ReceiveTimeout(timeout time.Duration) (interface{}, error) {
 			Payload: reply[3].(string),
 		}, nil
 	}
+
 	return nil, fmt.Errorf("redis: unsupported message name: %q", msgName)
 }
 

redis.go

@@ -32,32 +32,46 @@ func (c *baseClient) putConn(cn *conn, ei error) {
 }
 
 func (c *baseClient) process(cmd Cmder) {
-	cn, err := c.conn()
-	if err != nil {
-		cmd.setErr(err)
-		return
-	}
+	for i := 0; i <= c.opt.MaxRetries; i++ {
+		if i > 0 {
+			cmd.reset()
+		}
 
-	if timeout := cmd.writeTimeout(); timeout != nil {
-		cn.writeTimeout = *timeout
-	} else {
-		cn.writeTimeout = c.opt.WriteTimeout
-	}
+		cn, err := c.conn()
+		if err != nil {
+			cmd.setErr(err)
+			return
+		}
 
-	if timeout := cmd.readTimeout(); timeout != nil {
-		cn.readTimeout = *timeout
-	} else {
-		cn.readTimeout = c.opt.ReadTimeout
-	}
+		if timeout := cmd.writeTimeout(); timeout != nil {
+			cn.WriteTimeout = *timeout
+		} else {
+			cn.WriteTimeout = c.opt.WriteTimeout
+		}
 
-	if err := cn.writeCmds(cmd); err != nil {
+		if timeout := cmd.readTimeout(); timeout != nil {
+			cn.ReadTimeout = *timeout
+		} else {
+			cn.ReadTimeout = c.opt.ReadTimeout
+		}
+
+		if err := cn.writeCmds(cmd); err != nil {
+			c.putConn(cn, err)
+			cmd.setErr(err)
+			if shouldRetry(err) {
+				continue
+			}
+			return
+		}
+
+		err = cmd.parseReply(cn.rd)
 		c.putConn(cn, err)
-		cmd.setErr(err)
+		if shouldRetry(err) {
+			continue
+		}
+
 		return
 	}
-
-	err = cmd.parseReply(cn.rd)
-	c.putConn(cn, err)
 }
 
 // Close closes the client, releasing any open resources.
@@ -105,6 +119,10 @@ type Options struct {
 	// than specified in this option.
 	// Default: 0 = no eviction
 	IdleTimeout time.Duration
+
+	// MaxRetries specifies maximum number of times client will retry
+	// failed command. Default is to not retry failed command.
+	MaxRetries int
 }
 
 func (opt *Options) getDialer() func() (net.Conn, error) {
@@ -157,6 +175,8 @@ func (opt *Options) options() *options {
 		DialTimeout:  opt.getDialTimeout(),
 		ReadTimeout:  opt.ReadTimeout,
 		WriteTimeout: opt.WriteTimeout,
+
+		MaxRetries: opt.MaxRetries,
 	}
 }
 
@@ -172,6 +192,8 @@ type options struct {
 	DialTimeout  time.Duration
 	ReadTimeout  time.Duration
 	WriteTimeout time.Duration
+
+	MaxRetries int
 }
 
 func (opt *options) connPoolOptions() *connPoolOptions {

redis_test.go

@@ -124,6 +124,23 @@ var _ = Describe("Client", func() {
 		Expect(db1.FlushDb().Err()).NotTo(HaveOccurred())
 	})
 
+	It("should retry command on network error", func() {
+		Expect(client.Close()).NotTo(HaveOccurred())
+
+		client = redis.NewClient(&redis.Options{
+			Addr:       redisAddr,
+			MaxRetries: 1,
+		})
+
+		// Put bad connection in the pool.
+		cn, err := client.Pool().Get()
+		Expect(err).NotTo(HaveOccurred())
+		cn.SetNetConn(newBadNetConn())
+		Expect(client.Pool().Put(cn)).NotTo(HaveOccurred())
+
+		err = client.Ping().Err()
+		Expect(err).NotTo(HaveOccurred())
+	})
 })
 
 //------------------------------------------------------------------------------
@@ -266,6 +283,24 @@ func BenchmarkPipeline(b *testing.B) {
 
 //------------------------------------------------------------------------------
 
+type badNetConn struct {
+	net.TCPConn
+}
+
+var _ net.Conn = &badNetConn{}
+
+func newBadNetConn() net.Conn {
+	return &badNetConn{}
+}
+
+func (badNetConn) Read([]byte) (int, error) {
+	return 0, net.UnknownNetworkError("badNetConn")
+}
+
+func (badNetConn) Write([]byte) (int, error) {
+	return 0, net.UnknownNetworkError("badNetConn")
+}
+
 // Replaces ginkgo's Eventually.
 func waitForSubstring(fn func() string, substr string, timeout time.Duration) error {
 	var s string