Django视图函数执行，不在主线程中，直接

loop = asyncio.new_event_loop()  # 更不能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

        """

        start_time = time.time()

        loop = asyncio.new_event_loop()  # 或 loop = asyncio.SelectorEventLoop()

        asyncio.set_event_loop(loop)

        self.loop = loop

        try:

            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):

        """

         也可以用回调函数处理results

        task1 = self.loop.run_in_executor(None, self.io_task1, 2)

        future1 = asyncio.ensure_future(task1)

        future1.add_done_callback(callback)

        def callback(self, future):

            print("callback:",future.result())

        """

        tasks = (

            self.make_future(self.io_task1, 2),

            self.make_future(self.io_task2, 2)

        )

        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

    """

    # python3.5之前无async await写法

    import types

    @types.coroutine

    # @asyncio.coroutine  # 这个也行

    def make_future(self, func, *args):

        future = self.loop.run_in_executor(None, func, *args)

        response = yield from 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

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)

        with ThreadPoolExecutor(len(tasks)) as executor:

            for task in tasks:

                future = executor.submit(task, 2)

                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):

        """

        处理io任务执行结果，也可以用future.add_done_callback(self.get_result)

        def get(self, request, *args, **kargs):

            start_time = time.time()

            future_set = set()

            tasks = (self.io_task1, self.io_task2)

            with ThreadPoolExecutor(len(tasks)) as executor:

                for task in tasks:

                    future = executor.submit(task, 2).add_done_callback(self.get_result)

                    future_set.add(future)

            for future in as_completed(future_set):

                error = future.exception()

                print(dir(future))

                if error is not None:

                    raise error

            self.results = results = []

            end_time = time.time()

            return JsonResponse({'results': results, 'cost_time': (end_time - start_time)})

        def get_result(self, future):

            self.results.append(future.result())

        """

        results = []

        for future in future_set:

            results.append(future.result())

        return results

    def io_task1(self, sleep_time):

        time.sleep(sleep_time)

        return 10

    def io_task2(self, sleep_time):

        time.sleep(sleep_time)

        return 66

 
附tornado中不依赖异步库实现异步非阻塞

from tornado.web import RequestHandler

from concurrent.futures import ThreadPoolExecutor

class NonBlockingHandler(RequestHandler):

    """

    不依赖tornado的异步库实现异步非阻塞

    使用 gen.coroutine 装饰器编写异步函数，如果库本身不支持异步，那么响应任然是阻塞的。

    在 Tornado 中有个装饰器能使用 ThreadPoolExecutor 来让阻塞过程编程非阻塞，

    其原理是在 Tornado 本身这个线程之外另外启动一个线程来执行阻塞的程序，从而让 Tornado 变得非阻塞

    """

    executor = ThreadPoolExecutor(max_workers=2)

    # executor默认需为这个名字，否则@run_on_executor(executor='_thread_pool')自定义名字，经测试max_workers也可以等于1

    @coroutine  # 使用@coroutine这个装饰器加yield关键字，或者使用async加await关键字

    def get(self, *args, **kwargs):

        second = yield self.blocking_task(20)

        self.write('noBlocking Request: {}'.format(second))

    """

    async def get(self, *args, **kwargs):

        second = await self.blocking_task(5)

        self.write('noBlocking Request: {}'.format(second))

        """

    @run_on_executor

    def blocking_task(self, second):

        """

        阻塞任务

        """

        time.sleep(second)

        return second

参考 https://blog.csdn.net/qq_34367804/article/details/75046718

　　https://www.cnblogs.com/zhaof/p/8490045.html

　　https://stackoverflow.com/questions/41594266/asyncio-with-django

巴特西

如何在django视图中使用asyncio（协程）和ThreadPoolExecutor(多线程)

RuntimeError: There is no current event loop in thread

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