Redigo Connection Pool Code Analysis

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Structural Body Analysis

type Pool struct {    // 用来创建redis连接的方法    Dial func() (Conn, error)    // 如果设置了给func,那么每次p.Get()的时候都会调用改方法来验证连接的可用性    TestOnBorrow func(c Conn, t time.Time) error    // 定义连接池中最大连接数（超过这个数会关闭老的链接，总会保持这个数）    MaxIdle int    // 当前连接池中可用的链接数.    MaxActive int    // 定义链接的超时时间，每次p.Get()的时候会检测这个连接是否超时（超时会关闭，并释放可用连接数）.    IdleTimeout time.Duration    // 当可用连接数为0是，那么当wait=true,那么当调用p.Get()时，会阻塞等待，否则，返回nil.    Wait bool    // 读写锁控制.    mu     sync.Mutex    // 用来条件控制，这里主要是当链接被关闭时，提醒在等待的进程可以使用了，或者可以自行创建了    cond   *sync.Cond    // 当前连接池是否已经关闭    closed bool    // 当前可用的链接数    active int    // 链接存储在一个栈中.    idle list.List}

Connection pooling Shutdown method

func (p *Pool) Close() error {    p.mu.Lock()    // 获取连接池所有链接栈    idle := p.idle    // 重新初始化    p.idle.Init()    // 标示已经关闭    p.closed = true    // 控制可用连接数    p.active -= idle.Len()    // 如果当前有进程正在等待获取的话，则通知可以获取或者自行创建    if p.cond != nil {        p.cond.Broadcast()    }    p.mu.Unlock()    // 遍历栈，逐个关闭链接    for e := idle.Front(); e != nil; e = e.Next() {        e.Value.(idleConn).c.Close()    }    return nil}

Release a link

func (p *Pool) release() {    // 当链接超时，或者ping不通，或者创建失败，则立即使用链接表示    p.active -= 1    // 如果已经有进程在之前等待了，则通知其使用或者自行创建    if p.cond != nil {        p.cond.Signal()    }}

Close connection

func (p *Pool) put(c Conn, forceClose bool) error {    err := c.Err()    p.mu.Lock()    // 如果连接池没有关闭，并且不是强制关闭的    if !p.closed && err == nil && !forceClose {        // 把指定的链接放在空闲栈首位        p.idle.PushFront(idleConn{t: nowFunc(), c: c})        // 如果栈的长度大于指定长度，则吧最后一个（可能超时）剔除        if p.idle.Len() > p.MaxIdle {            c = p.idle.Remove(p.idle.Back()).(idleConn).c        } else {            c = nil        }    }    if c == nil {        //成功放回空闲连接通知其他阻塞的进程        if p.cond != nil {            p.cond.Signal()        }        p.mu.Unlock()        return nil    }    // 减少active计数（感觉这里可以不用处理，上面如果是替换的话）    p.release()    p.mu.Unlock()    // 关闭连接    return c.Close()}

Get links

Func (P *pool) get (Conn, error) {P.mu.lock ()//Handle old link (detect if timeout) 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)//The time that the link was created plus whether the time-out is less than the current time if Ic.t.add (timeout). After (Nowfunc ()) {break}//Timeout link, remove P.idle.remove (e)//available from stack            The number of connections is reduced and other waiting processes are notified to process P.release () P.mu.unlock ()//Close the current connection ic.c.close ()            P.mu.lock ()}} for {//Gets an available link from the list of connection stacks for I, N: = 0, P.idle.len (); i < n; i++ {             Connect from the front of the idle list, then it must be the connection you just used e: = P.idle.front () if E = = nil {break} Type assertion IC: = E.value.        (idleconn)//Remove P.idle.remove from the stack (e) Test: = P.testonborrow    P.mu.unlock ()//Check link if test = Nil by using Check link function | |            Test (IC.C, ic.t) = = Nil {return ic.c, nil}//Check for problems, close connection ic.c.close ()        P.mu.lock ()//reduces the number of available connections and notifies other processes that processing p.release ()}//detects if the connection pool has been closed. If p.closed {p.mu.unlock () return nil, errors. New ("Redigo:get on Closed Pool")}//If the number of available connections is 0 or less than the maximum available number of available connections, create if p.maxactive = = 0 | | P.active < p.maxactive {dial: = p.dial p.active + 1 P.mu.unlock ()//Connect RE                Dis Server c, err: = dial ()//connection failure closed if err! = Nil {P.mu.lock ()        P.release () P.mu.unlock () c = nil} return c, err}        If no wait is configured, then return nil if!p.wait {p.mu.unlock () return nil, errpoolexhausted} If you configure the wait, thatInitialize, and start waiting until there is a process to notify the link number enough or you can create if P.cond = = Nil {P.cond = sync. Newcond (&AMP;P.MU)} p.cond.wait ()}}