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