后台程序处理（二） python threading

由于协程没办法完成（一）中所说的任务模式

接下来就尝试一下使用线程和队列来实现一下这个功能

在实现之前，我们先明确一个问题——python的线程是伪并发的。同一时间只能有一个线程在运行。具体怎样的运作方式由解释器决定

然后回顾一下上一章遇到的问题——return以后，需要另外一个线程去检测之前的操作是否执行成功

因此程序的流程设计应该是这样的：

# 大致流程步骤如下
# 1.获取参数（接口被访问时触发）
request_data = request.form
# 2.根据参数查询内容
target = Target.query.filter_by(id=request_data).first()
# 3.将结果插入队列
ans_queue.put(target)
# 4.激活线程
thread.set()
# 5.将结果从队列中取出
ans_queue.get()
# 6.处理结果
check()
# 7.将线程休眠（阻塞）
thread.event.clear()

这样设计的考虑主要是以下几点：

1.简单

2.入队可以保证消息按时间顺序被处理

3.出队可以保证当队列不为空时，检查线程会执行到队列为空为止。免去不必要的唤醒检查。然后在有消息入队时被重新激活

4.其实我们的设计正常来说不会出现3中的检查情况。基本上队列一旦有消息入队，线程就会启动并清空队列

5.入队可以保证消息的完整和独立性，每次请求得到的数据入队后，队列中都是一列数组。处理逻辑更清晰

6.队列中的数据不出栈是不可见的

7.我就是宁愿用全局队列也不想用全局变量

实际接口代码和线程代码如下：

A.队列和线程代码

# 消息队列
lock_queue = Queue()


def check_kill(event):
    while True:
        # check queue
        if lock_queue.empty() is True:
            event.clear()
        # wait event
        if event.is_set() is not True:
            event.wait()
        # do some work
        sids, serials, minutes, hosts, insts, opasses, ospasses = [], [], [], [], [], [], []

        # get data until queue empty or datas more than 10
        if lock_queue.empty() is not True:
            data = lock_queue.get()
            for i in data:
                sid, serial, minute, host, inst, opass, ospass = i.split(',')
                sids.append(sid)
                serials.append(serial)
                minutes.append(minute)
                hosts.append(host)
                insts.append(inst)
                opasses.append(opass)
                ospasses.append(ospass)

        # init the command
        kill_command = 'kill -9'

        # each time we deal less or equal 10 check
        for i in range(len(minutes)):
            current = datetime.datetime.now().minute
            if current >= int(minutes[i]):
                passtime = current - int(minutes[i])
            else:
                passtime = current + 60 - int(minutes[i])
            
            print("passtime is", passtime)
            if (5 - passtime) >= 0:
                time.sleep((5 - passtime)*60)

            # split piece of list
            sql_sids, sids = sids[0], sids[1:]
            sql_serials, serials = serials[0], serials[1:]
            sql_hosts, hosts = hosts[0], hosts[1:]
            sql_insts, insts = insts[0], insts[1:]
            sql_opass, opasses = opasses[0], opasses[1:]
            sql_ospass, ospasses = ospasses[0], ospasses[1:]

            print("data", sql_hosts, sql_insts, sql_serials, sql_sids)
            # create cursor
            
            try:
                conn = sqlite3.connect('data-dev.sqlite')
                c = conn.cursor()
                cu = c.execute("select ouser,oport,osport,osuser from tool_target where host='%s' and inst='%s'" % (sql_hosts, sql_insts))

                result = cu.fetchall()

                ouser = result[0][0]
                opass = sql_opass
                str_conn = (sql_hosts
                            + ':'
                            + str(result[0][1])
                            + '/'
                            + sql_insts)
                odb = cx_Oracle.connect(ouser, opass, str_conn)
                cursor = odb.cursor()

                # select to find if lock exist
                sql = '''select b.spid, a.sid, a.serial#, a.event from v$session a, v$process b  
                        where a.sid = %s and a.serial# = %s ''' % (sql_sids, sql_serials)
                
                cursor.execute(sql)
                answer = cursor.fetchall()
                print("answer is", answer)
                kill_command += ' ' + answer[0][0]

                s = paramiko.SSHClient()
                s.load_system_host_keys()
                s.set_missing_host_key_policy(paramiko.AutoAddPolicy())
                s.connect(sql_hosts, result[0][2], result[0][3], sql_ospass)
                stdin, stdout, stderr = s.exec_command(kill_command)
                stdout.read()
                print('------------------------')
                s.close()
                cursor.close()
                odb.close()
                c.close()
                conn.close()
            except:
                pass


txkill_ready = threading.Event()
t1 = threading.Thread(target=check_kill, args=(txkill_ready,), name='t1')
t1.start()
# txkill_ready.set()

B.接口代码

@main.route('/txlock/startkillurl', methods=['POST'])
def start_kill_url():
    if request.method == 'POST':
        cmd = request.form.getlist('list')[0]
        host = request.form.getlist('host')[0]
        inst = request.form.getlist('inst')[0]
        # print(len(cmd))
        # cmd.replace("
", "")
        # cmd.replace("	", "")
        # print(len(cmd))
        
        tooltarget = ToolTarget.query.filter_by(host=host, inst=inst).first()
        ouser = tooltarget.ouser
        opass = ToolTarget.de_rsa(pwd=tooltarget.opass)
        ospass = ToolTarget.de_rsa(pwd=tooltarget.ospass)
        str_conn = (tooltarget.host
                    + ':'
                    + str(tooltarget.oport)
                    + '/'
                    + tooltarget.inst)
        odb = cx_Oracle.connect(ouser, opass, str_conn)
        cursor = odb.cursor()

        # add into queue
        c = re.findall('d*,d*', cmd)
        d = [i+','+str(datetime.datetime.now().minute)+','+host+','+inst+','+opass+','+ospass for i in c]
        # data example : ['15,5,17', '16,23,17', '14,5,17', '142,1,17']
        lock_queue.put(d)
        txkill_ready.set()

        try:
            cursor.execute(cmd)
            # pass
        except:
            return "执行失败,关闭弹窗后会自动刷新列表"
    return "执行成功,关闭弹窗后会自动刷新列表"