distribution/vendor/github.com/garyburd/redigo/redis/pool.go
Olivier Gambier 77e69b9cf3 Move to vendor
Signed-off-by: Olivier Gambier <olivier@docker.com>
2016-03-22 10:45:49 -07:00

389 lines
9.8 KiB
Go

// Copyright 2012 Gary Burd
//
// Licensed under the Apache License, Version 2.0 (the "License"): you may
// not use this file except in compliance with the License. You may obtain
// a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations
// under the License.
package redis
import (
"bytes"
"container/list"
"crypto/rand"
"crypto/sha1"
"errors"
"io"
"strconv"
"sync"
"time"
"github.com/garyburd/redigo/internal"
)
var nowFunc = time.Now // for testing
// ErrPoolExhausted is returned from a pool connection method (Do, Send,
// Receive, Flush, Err) when the maximum number of database connections in the
// pool has been reached.
var ErrPoolExhausted = errors.New("redigo: connection pool exhausted")
var (
errPoolClosed = errors.New("redigo: connection pool closed")
errConnClosed = errors.New("redigo: connection closed")
)
// Pool maintains a pool of connections. The application calls the Get method
// to get a connection from the pool and the connection's Close method to
// return the connection's resources to the pool.
//
// The following example shows how to use a pool in a web application. The
// application creates a pool at application startup and makes it available to
// request handlers using a global variable.
//
// func newPool(server, password string) *redis.Pool {
// return &redis.Pool{
// MaxIdle: 3,
// IdleTimeout: 240 * time.Second,
// Dial: func () (redis.Conn, error) {
// c, err := redis.Dial("tcp", server)
// if err != nil {
// return nil, err
// }
// if _, err := c.Do("AUTH", password); err != nil {
// c.Close()
// return nil, err
// }
// return c, err
// },
// TestOnBorrow: func(c redis.Conn, t time.Time) error {
// _, err := c.Do("PING")
// return err
// },
// }
// }
//
// var (
// pool *redis.Pool
// redisServer = flag.String("redisServer", ":6379", "")
// redisPassword = flag.String("redisPassword", "", "")
// )
//
// func main() {
// flag.Parse()
// pool = newPool(*redisServer, *redisPassword)
// ...
// }
//
// A request handler gets a connection from the pool and closes the connection
// when the handler is done:
//
// func serveHome(w http.ResponseWriter, r *http.Request) {
// conn := pool.Get()
// defer conn.Close()
// ....
// }
//
type Pool struct {
// Dial is an application supplied function for creating and configuring a
// connection
Dial func() (Conn, error)
// TestOnBorrow is an optional application supplied function for checking
// the health of an idle connection before the connection is used again by
// the application. Argument t is the time that the connection was returned
// to the pool. If the function returns an error, then the connection is
// closed.
TestOnBorrow func(c Conn, t time.Time) error
// Maximum number of idle connections in the pool.
MaxIdle int
// Maximum number of connections allocated by the pool at a given time.
// When zero, there is no limit on the number of connections in the pool.
MaxActive int
// Close connections after remaining idle for this duration. If the value
// is zero, then idle connections are not closed. Applications should set
// the timeout to a value less than the server's timeout.
IdleTimeout time.Duration
// If Wait is true and the pool is at the MaxIdle limit, then Get() waits
// for a connection to be returned to the pool before returning.
Wait bool
// mu protects fields defined below.
mu sync.Mutex
cond *sync.Cond
closed bool
active int
// Stack of idleConn with most recently used at the front.
idle list.List
}
type idleConn struct {
c Conn
t time.Time
}
// NewPool creates a new pool. This function is deprecated. Applications should
// initialize the Pool fields directly as shown in example.
func NewPool(newFn func() (Conn, error), maxIdle int) *Pool {
return &Pool{Dial: newFn, MaxIdle: maxIdle}
}
// Get gets a connection. The application must close the returned connection.
// This method always returns a valid connection so that applications can defer
// error handling to the first use of the connection. If there is an error
// getting an underlying connection, then the connection Err, Do, Send, Flush
// and Receive methods return that error.
func (p *Pool) Get() Conn {
c, err := p.get()
if err != nil {
return errorConnection{err}
}
return &pooledConnection{p: p, c: c}
}
// ActiveCount returns the number of active connections in the pool.
func (p *Pool) ActiveCount() int {
p.mu.Lock()
active := p.active
p.mu.Unlock()
return active
}
// Close releases the resources used by the pool.
func (p *Pool) Close() error {
p.mu.Lock()
idle := p.idle
p.idle.Init()
p.closed = true
p.active -= idle.Len()
if p.cond != nil {
p.cond.Broadcast()
}
p.mu.Unlock()
for e := idle.Front(); e != nil; e = e.Next() {
e.Value.(idleConn).c.Close()
}
return nil
}
// release decrements the active count and signals waiters. The caller must
// hold p.mu during the call.
func (p *Pool) release() {
p.active -= 1
if p.cond != nil {
p.cond.Signal()
}
}
// get prunes stale connections and returns a connection from the idle list or
// creates a new connection.
func (p *Pool) get() (Conn, error) {
p.mu.Lock()
// Prune stale connections.
if timeout := p.IdleTimeout; timeout > 0 {
for i, n := 0, p.idle.Len(); i < n; i++ {
e := p.idle.Back()
if e == nil {
break
}
ic := e.Value.(idleConn)
if ic.t.Add(timeout).After(nowFunc()) {
break
}
p.idle.Remove(e)
p.release()
p.mu.Unlock()
ic.c.Close()
p.mu.Lock()
}
}
for {
// Get idle connection.
for i, n := 0, p.idle.Len(); i < n; i++ {
e := p.idle.Front()
if e == nil {
break
}
ic := e.Value.(idleConn)
p.idle.Remove(e)
test := p.TestOnBorrow
p.mu.Unlock()
if test == nil || test(ic.c, ic.t) == nil {
return ic.c, nil
}
ic.c.Close()
p.mu.Lock()
p.release()
}
// Check for pool closed before dialing a new connection.
if p.closed {
p.mu.Unlock()
return nil, errors.New("redigo: get on closed pool")
}
// Dial new connection if under limit.
if p.MaxActive == 0 || p.active < p.MaxActive {
dial := p.Dial
p.active += 1
p.mu.Unlock()
c, err := dial()
if err != nil {
p.mu.Lock()
p.release()
p.mu.Unlock()
c = nil
}
return c, err
}
if !p.Wait {
p.mu.Unlock()
return nil, ErrPoolExhausted
}
if p.cond == nil {
p.cond = sync.NewCond(&p.mu)
}
p.cond.Wait()
}
}
func (p *Pool) put(c Conn, forceClose bool) error {
err := c.Err()
p.mu.Lock()
if !p.closed && err == nil && !forceClose {
p.idle.PushFront(idleConn{t: nowFunc(), c: c})
if p.idle.Len() > p.MaxIdle {
c = p.idle.Remove(p.idle.Back()).(idleConn).c
} else {
c = nil
}
}
if c == nil {
if p.cond != nil {
p.cond.Signal()
}
p.mu.Unlock()
return nil
}
p.release()
p.mu.Unlock()
return c.Close()
}
type pooledConnection struct {
p *Pool
c Conn
state int
}
var (
sentinel []byte
sentinelOnce sync.Once
)
func initSentinel() {
p := make([]byte, 64)
if _, err := rand.Read(p); err == nil {
sentinel = p
} else {
h := sha1.New()
io.WriteString(h, "Oops, rand failed. Use time instead.")
io.WriteString(h, strconv.FormatInt(time.Now().UnixNano(), 10))
sentinel = h.Sum(nil)
}
}
func (pc *pooledConnection) Close() error {
c := pc.c
if _, ok := c.(errorConnection); ok {
return nil
}
pc.c = errorConnection{errConnClosed}
if pc.state&internal.MultiState != 0 {
c.Send("DISCARD")
pc.state &^= (internal.MultiState | internal.WatchState)
} else if pc.state&internal.WatchState != 0 {
c.Send("UNWATCH")
pc.state &^= internal.WatchState
}
if pc.state&internal.SubscribeState != 0 {
c.Send("UNSUBSCRIBE")
c.Send("PUNSUBSCRIBE")
// To detect the end of the message stream, ask the server to echo
// a sentinel value and read until we see that value.
sentinelOnce.Do(initSentinel)
c.Send("ECHO", sentinel)
c.Flush()
for {
p, err := c.Receive()
if err != nil {
break
}
if p, ok := p.([]byte); ok && bytes.Equal(p, sentinel) {
pc.state &^= internal.SubscribeState
break
}
}
}
c.Do("")
pc.p.put(c, pc.state != 0)
return nil
}
func (pc *pooledConnection) Err() error {
return pc.c.Err()
}
func (pc *pooledConnection) Do(commandName string, args ...interface{}) (reply interface{}, err error) {
ci := internal.LookupCommandInfo(commandName)
pc.state = (pc.state | ci.Set) &^ ci.Clear
return pc.c.Do(commandName, args...)
}
func (pc *pooledConnection) Send(commandName string, args ...interface{}) error {
ci := internal.LookupCommandInfo(commandName)
pc.state = (pc.state | ci.Set) &^ ci.Clear
return pc.c.Send(commandName, args...)
}
func (pc *pooledConnection) Flush() error {
return pc.c.Flush()
}
func (pc *pooledConnection) Receive() (reply interface{}, err error) {
return pc.c.Receive()
}
type errorConnection struct{ err error }
func (ec errorConnection) Do(string, ...interface{}) (interface{}, error) { return nil, ec.err }
func (ec errorConnection) Send(string, ...interface{}) error { return ec.err }
func (ec errorConnection) Err() error { return ec.err }
func (ec errorConnection) Close() error { return ec.err }
func (ec errorConnection) Flush() error { return ec.err }
func (ec errorConnection) Receive() (interface{}, error) { return nil, ec.err }