【网络通信】连接池：数据库连接的复用与上限

---连接池：空闲连接的复用
local Pool = { idle = {}, active = 0, max = 20 }

function Pool.acquire()
    -- 优先取空闲连接
    local conn = table.remove(Pool.idle)
    if conn then
        Pool.active = Pool.active + 1
        return conn
    end
    -- 池满：等待或报错
    if Pool.active >= Pool.max then
        return nil, '连接池已满'
    end
    local conn = DB.connect()
    Pool.active = Pool.active + 1
    return conn
end

function Pool.release(conn)
    conn:reset()
    table.insert(Pool.idle, conn)
    Pool.active = Pool.active - 1
end

---池的参数：上限与超时的配置
setontimerex(137, 30)
function Pool.stats()
    local waitQ = Pool.waitingCount()
    Ops.log(string.format(
        '池: 活跃%d 空闲%d 等待%d',
        Pool.active, #Pool.idle, waitQ))
    -- 等待队列持续有量：扩池的信号
    if waitQ > 10 then
        Ops.alert('连接等待堆积，考虑扩池')
    end
end