首页 > 编程语言 > Django如何使用asyncio协程和ThreadPoolExecutor多线程
2020
10-13

Django如何使用asyncio协程和ThreadPoolExecutor多线程

Django视图函数执行，不在主线程中，直接loop = asyncio.new_event_loop()
# 不能loop = asyncio.get_event_loop() 会触发RuntimeError: There is no current event loop in thread

因为asyncio程序中的每个线程都有自己的事件循环，但它只会在主线程中为你自动创建一个事件循环。所以如果你asyncio.get_event_loop在主线程中调用一次，它将自动创建一个循环对象并将其设置为默认值，但是如果你在一个子线程中再次调用它，你会得到这个错误。相反，您需要在线程启动时显式创建/设置事件循环：

loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)

在Django单个视图中使用asyncio实例代码如下（有多个IO任务时）

from django.views import View
import asyncio
import time
from django.http import JsonResponse
 
 
class TestAsyncioView(View):
  def get(self, request, *args, **kwargs):
    """
    利用asyncio和async await关键字（python3.5之前使用yield）实现协程
    """
    self.id = 5
    start_time = time.time()
 
    '''
    # 同步执行
    # results = [self.io_task1(self.id),
    # self.io_task2(self.id),
    # self.io_task2(self.id)]
    '''
 
 
    loop = asyncio.new_event_loop() # 或 loop = asyncio.SelectorEventLoop()
    asyncio.set_event_loop(loop)
    self.loop = loop
 
    works = [
      asyncio.ensure_future(self.io_task3(5)),
      asyncio.ensure_future(self.io_task3(5)),
      asyncio.ensure_future(self.io_task3(5)),
      asyncio.ensure_future(self.io_task3(5)),
      asyncio.ensure_future(self.io_task3(5)),
 
    ]
 
    try:
 
      results = loop.run_until_complete(asyncio.gather(*works)) # 两种写法
      # results = loop.run_until_complete(self.gather_tasks())
    finally:
      loop.close()
    end_time = time.time()
    return JsonResponse({'results': results, 'cost_time': (end_time - start_time)})
 
  async def gather_tasks(self):
 
    tasks = (
      self.make_future(self.io_task1, self.id),
      self.make_future(self.io_task2, self.id),
      self.make_future(self.io_task2, self.id),
      self.make_future(self.io_task1, self.id),
      self.make_future(self.io_task2, self.id),
      self.make_future(self.io_task2, self.id),
    )
    results = await asyncio.gather(*tasks)
    return results
 
  async def make_future(self, func, *args):
    future = self.loop.run_in_executor(None, func, *args)
    response = await future
    return response
 
  def io_task1(self, sleep_time):
    time.sleep(sleep_time)
    return 66
 
  def io_task2(self, sleep_time):
    time.sleep(sleep_time)
    return 77
 
  async def io_task3(self, sleep_time):
    # await asyncio.sleep(sleep_time)
    s = await self.do(sleep_time)
    return s
 
  async def do(self, sleep_time):
    await asyncio.sleep(sleep_time)
    return 66

在Django单个视图中使用ThreadPoolExecutor实例代码如下（有多个IO任务时）

from django.views import View
import time
from concurrent.futures import ThreadPoolExecutor, as_completed
 
 
class TestThreadView(View):
  def get(self, request, *args, **kargs):
    start_time = time.time()
    future_set = set()
    tasks = (self.io_task1, self.io_task2, self.io_task2, self.io_task1, self.io_task2, self.io_task2)
    with ThreadPoolExecutor(len(tasks)) as executor:
      for task in tasks:
        future = executor.submit(task, 5)
        future_set.add(future)
    for future in as_completed(future_set):
      error = future.exception()
      if error is not None:
        raise error
    results = self.get_results(future_set)
    end_time = time.time()
    return JsonResponse({'results': results, 'cost_time': (end_time - start_time)})
 
  def get_results(self, future_set):
 
    results = []
    for future in future_set:
      results.append(future.result())
    return results
 
  def io_task1(self, sleep_time):
    time.sleep(sleep_time)
    return 66
 
  def io_task2(self, sleep_time):
    time.sleep(sleep_time)
    return 77

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持自学编程网。

编程技巧