后台程序处理（二） python threading - queue 模块使用

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("\n", "")
         # cmd.replace("\t", "")
         # 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"