Python菜鸟之路：Python基础-线程池注释

import sys
import threading
import Queue
import traceback

# 定义一些Exception，用于自定义异常处理

class NoResultsPending(Exception):
    """All works requests have been processed"""
    pass

class NoWorkersAvailable(Exception):
    """No worket threads available to process remaining requests."""
    pass

def _handle_thread_exception(request, exc_info):
    """默认的异常处理函数，只是简单的打印"""
    traceback.print_exception(*exc_info)

#classes 

class WorkerThread(threading.Thread):
    """后台线程，真正的工作线程，从请求队列(requestQueue)中获取work，
    并将执行后的结果添加到结果队列(resultQueue)"""
    def __init__(self,requestQueue,resultQueue,poll_timeout=5,**kwds):
        threading.Thread.__init__(self,**kwds)
        '''设置为守护进行'''
        self.setDaemon(True)
        self._requestQueue = requestQueue
        self._resultQueue = resultQueue
        self._poll_timeout = poll_timeout
        '''设置一个flag信号，用来表示该线程是否还被dismiss,默认为false'''
        self._dismissed = threading.Event()
        self.start()
        
    def run(self):
        '''每个线程尽可能多的执行work，所以采用loop，
        只要线程可用，并且requestQueue有work未完成，则一直loop'''
        while True:
            if self._dismissed.is_set():
                break
            try:
                '''
                Queue.Queue队列设置了线程同步策略，并且可以设置timeout。
                一直block，直到requestQueue有值，或者超时
                '''
                request = self._requestQueue.get(True,self._poll_timeout)
            except Queue.Empty:
                continue
            else:
                '''之所以在这里再次判断dimissed，是因为之前的timeout时间里，很有可能，该线程被dismiss掉了'''
                if self._dismissed.is_set():
                    self._requestQueue.put(request)
                    break
                try:
                    '''执行callable，讲请求和结果以tuple的方式放入requestQueue'''
                    result = request.callable(*request.args,**request.kwds)
                    print self.getName()
                    self._resultQueue.put((request,result))
                except:
                    '''异常处理'''
                    request.exception = True
                    self._resultQueue.put((request,sys.exc_info()))
    
    def dismiss(self):
        '''设置一个标志，表示完成当前work之后，退出'''
        self._dismissed.set()


class WorkRequest:
    '''
    @param callable_:，可定制的，执行work的函数
    @param args: 列表参数
    @param kwds: 字典参数
    @param requestID: id
    @param callback: 可定制的，处理resultQueue队列元素的函数
    @param exc_callback:可定制的，处理异常的函数 
    '''
    def __init__(self,callable_,args=None,kwds=None,requestID=None,
                 callback=None,exc_callback=_handle_thread_exception):
        if requestID == None:
            self.requestID = id(self)
        else:
            try:
                self.requestID = hash(requestID)
            except TypeError:
                raise TypeError("requestId must be hashable")    
        self.exception = False
        self.callback = callback
        self.exc_callback = exc_callback
        self.callable = callable_
        self.args = args or []
        self.kwds = kwds or {}
        
    def __str__(self):
        return "WorkRequest id=%s args=%r kwargs=%r exception=%s" % 
            (self.requestID,self.args,self.kwds,self.exception)
            
class ThreadPool:
    '''
    @param num_workers:初始化的线程数量
    @param q_size,resq_size: requestQueue和result队列的初始大小
    @param poll_timeout: 设置工作线程WorkerThread的timeout，也就是等待requestQueue的timeout
    '''
    def __init__(self,num_workers,q_size=0,resq_size=0,poll_timeout=5):
        self._requestQueue = Queue.Queue(q_size)
        self._resultQueue = Queue.Queue(resq_size)
        self.workers = []
        self.dismissedWorkers = []
        self.workRequests = {} #设置个字典，方便使用
        self.createWorkers(num_workers,poll_timeout)

    def createWorkers(self,num_workers,poll_timeout=5):
        '''创建num_workers个WorkThread,默认timeout为5'''
        for i in range(num_workers):
            self.workers.append(WorkerThread(self._requestQueue,self._resultQueue,poll_timeout=poll_timeout))                           
    
    def dismissWorkers(self,num_workers,do_join=False):
        '''停用num_workers数量的线程，并加入dismiss_list'''
        dismiss_list = []
        for i in range(min(num_workers,len(self.workers))):
            worker = self.workers.pop()
            worker.dismiss()
            dismiss_list.append(worker)
        if do_join :
            for worker in dismiss_list:
                worker.join()
        else:
            self.dismissedWorkers.extend(dismiss_list)
    
    def joinAllDismissedWorkers(self):
        '''join 所有停用的thread'''
        #print len(self.dismissedWorkers)
        for worker in self.dismissedWorkers:
            worker.join()
        self.dismissedWorkers = []
    
    def putRequest(self,request ,block=True,timeout=None):
        assert isinstance(request,WorkRequest)
        assert not getattr(request,'exception',None)
        '''当queue满了，也就是容量达到了前面设定的q_size,它将一直阻塞，直到有空余位置，或是timeout'''
        self._requestQueue.put(request, block, timeout)
        self.workRequests[request.requestID] = request
        
    def poll(self,block = False):
        while True:
            if not self.workRequests:
                raise NoResultsPending
            elif block and not self.workers:
                raise NoWorkersAvailable
            try:
                '''默认只要resultQueue有值，则取出，否则一直block'''
                request , result = self._resultQueue.get(block=block)
                if request.exception and request.exc_callback:
                    request.exc_callback(request,result)
                if request.callback and not (request.exception and request.exc_callback):
                    request.callback(request,result)
                del self.workRequests[request.requestID]
            except Queue.Empty:
                break
    
    def wait(self):
        while True:
            try:
                self.poll(True)
            except NoResultsPending:
                break
    
    def workersize(self):
        return len(self.workers)
    
    def stop(self):
        '''join 所有的thread,确保所有的线程都执行完毕'''
        self.dismissWorkers(self.workersize(),True)
        self.joinAllDismissedWorkers()

if __name__=='__main__':
    import random
    import time
    import datetime
    def do_work(data):
        time.sleep(random.randint(1,3))
        res = str(datetime.datetime.now()) + "" +str(data)
        return res
    
    def print_result(request,result):
        print "---Result from request %s : %r" % (request.requestID,result)
    
    main = ThreadPool(3)
    for i in range(40):
        req = WorkRequest(do_work,args=[i],kwds={},callback=print_result)
        main.putRequest(req)
        print "work request #%s added." % req.requestID
    
    print '-'*20, main.workersize(),'-'*20
    
    counter = 0
    while True:
        try:
            time.sleep(0.5)
            main.poll()
            if(counter==5):
                print "Add 3 more workers threads"
                main.createWorkers(3)
                print '-'*20, main.workersize(),'-'*20
            if(counter==10):
                print "dismiss 2 workers threads"
                main.dismissWorkers(2)
                print '-'*20, main.workersize(),'-'*20
            counter+=1
        except NoResultsPending:
            print "no pending results"
            break
    
    main.stop()
    print "Stop"

# 线程池注释

import queue
import threading
import contextlib
import time

StopEvent = object()


class ThreadPool(object):

    def __init__(self, max_num, max_task_num = None):
        if max_task_num:
            self.q = queue.Queue(max_task_num) # 初始化队列
        else:
            self.q = queue.Queue() # 初始化队列
        self.max_num = max_num
        self.cancel = False
        self.terminal = False
        self.generate_list = [] # 定义列表，存储当前已经生成的线程
        self.free_list = [] # 定义列表，存储当前空闲线程

    def run(self, func, args, callback=None):
        """
        线程池执行一个任务
        :param func: 任务函数
        :param args: 任务函数所需参数
        :param callback: 任务执行失败或成功后执行的回调函数，回调函数有两个参数1、任务函数执行状态；2、任务函数返回值（默认为None，即：不执行回调函数）
        :return: 如果线程池已经终止，则返回True否则None
        """
        if self.cancel:
            return
        if len(self.free_list) == 0 and len(self.generate_list) < self.max_num: # 如果当前线程数未达到上限，且无空闲线程，则创建线程
            self.generate_thread()
        w = (func, args, callback,) # 生成任务元组
        self.q.put(w) # 将任务放到队列中

    def generate_thread(self):
        """
        创建一个线程
        """
        t = threading.Thread(target=self.call)
        t.start()

    def call(self):
        """
        循环去获取任务函数并执行任务函数
        """
        current_thread = threading.currentThread # 获取当前线程
        self.generate_list.append(current_thread) # 将获取到的线程加入到列表中

        event = self.q.get() # 从队列中获取任务元组
        while event != StopEvent: # 如果获取任务元组成功

            func, arguments, callback = event # 拆解任务元组
            try:
                result = func(*arguments) # 执行任务
                success = True
            except Exception as e: # 检测到任务执行异常，重置任务状态标识
                success = False
                result = None

            if callback is not None: # 如果callback函数已经定义，那么执行callback函数
                try:
                    callback(success, result)
                except Exception as e:
                    pass
            # 将当前线程设置为空闲
            # 等待任务来临--》有任务来了--》当前线程不再空闲
            # with块语句等价于
            # self.free_list.append(当前线程)
            # self.q.get()
            # self.free_list.remove(当前线程)
            with self.worker_state(self.free_list, current_thread): # 执行完任务后，再次取任务还是终止任务
                if self.terminal:# 检测到终止信号
                    event = StopEvent # 设置终止事件，下次while循环时，会执行else语句
                else:
                    event = self.q.get() # 阻塞等待任务
        else:
            self.generate_list.remove(current_thread) # 如果获取任务失败，说明任务已经全部执行完毕，则移除线程

    def close(self):
        """
        执行完所有的任务后，所有线程停止
        """
        self.cancel = True
        full_size = len(self.generate_list)
        while full_size: # 拒绝再加入新的任务，等待当前运行任务执行完毕后亭子
            self.q.put(StopEvent)
            full_size -= 1

    def terminate(self):
        """
        无论是否还有任务，终止线程
        """
        self.terminal = True # 如果线程列表中依然有线程，会去队列中get任务，但是此时检测到terminal信号，则循环取任务的过程被中断，线程被关闭、销毁

        while self.generate_list:
            self.q.put(StopEvent)

        self.q.empty()

    @contextlib.contextmanager # 将一个生成器函数转换成上下文管理器
    def worker_state(self, state_list, worker_thread):
        """
        用于记录线程中正在等待的线程数
        """
        state_list.append(worker_thread)
        try:
            yield # 遇到yield，就返回到执行event = self.q.get()
        finally: # 当event = self.q.get() 执行state_list.remove(worker_thread)
            state_list.remove(worker_thread)



# How to use


pool = ThreadPool(5)

def callback(status, result):
    # status, execute action status
    # result, execute action return value
    pass


def action(i):
    print(i)

for i in range(30):
    ret = pool.run(action, (i,), callback)

time.sleep(5)
print(len(pool.generate_list), len(pool.free_list))
print(len(pool.generate_list), len(pool.free_list))
# pool.close()
# pool.terminate()