为 Tornado 应用程序安装 AsyncIOMainLoop() 的合适位置在哪里

Question

所以我怀疑我看到的两种安装 AsyncIOMainLoop() 的方法中哪一种更正确。哪个更合适？

1st 当 AsyncIOMainLoop() 安装在 make_app() 代码中时：

class MainHandler(tornado.web.RequestHandler):
    async def get(self, *args, **kwargs):
        return self.write("OK")

    async def post(self, *args, **kwargs):
        return self.write("OK")

def make_app():
    tornado.platform.asyncio.AsyncIOMainLoop().install()
    return tornado.web.Application([(r"/", MainHandler),],
                                   debug=False)

def start_app():
    app = make_app()
    app.listen(8888)
    asyncio.get_event_loop().run_forever()


if __name__ == "__main__":
    start_app()

第二次在 start_app() 代码中安装 AsyncIOMainLoop() 时：

class MainHandler(tornado.web.RequestHandler):
    async def get(self, *args, **kwargs):
        return self.write("OK")

    async def post(self, *args, **kwargs):
        return self.write("OK")

def make_app():
    return tornado.web.Application([(r"/", MainHandler),],
                                   debug=False)

def start_app():
    tornado.platform.asyncio.AsyncIOMainLoop().install()
    app = make_app()
    app.listen(8888)
    asyncio.get_event_loop().run_forever()


if __name__ == "__main__":
    start_app()

您认为这两种方法中哪一种更合适？

对于第一个，我在一个 AsyncHTTPTestCase 套件中运行超过 2 个测试时遇到了问题，错误如下：

Traceback (most recent call last):
  File "/home/kamyanskiy/.local/share/virtualenvs/test-0zFWLpVX/lib/python3.6/site-packages/tornado/testing.py", line 380, in setUp
    self._app = self.get_app()
  File "/home/kamyanskiy/work/test/test_app.py", line 10, in get_app
    return web1.make_app()
  File "/home/kamyanskiy/work/test/web1.py", line 74, in make_app
    tornado.platform.asyncio.AsyncIOMainLoop().install()
  File "/home/kamyanskiy/.local/share/virtualenvs/test-0zFWLpVX/lib/python3.6/site-packages/tornado/ioloop.py", line 181, in install
    assert not IOLoop.initialized()
AssertionError

对于第二个，当 AsyncIOMainLoop() 安装在 start_app() 代码中时 - 测试运行正常，但在这里我怀疑在测试期间 AsyncIOMainLoop() 没有使用。

测试看起来像：

from tornado.testing import AsyncHTTPTestCase
import web1

class TestTornadoAppBase(AsyncHTTPTestCase):

    def get_app(self):
        return web1.make_app()

    # I have to uncomment this for 1st code example 
    # def tearDown(self):
    #    self.io_loop.clear_instance()  
    #    super().tearDown()

class TestGET(TestTornadoAppBase):
    def test_root_get_method(self):
        response = self.fetch("/")
        self.assertEqual(response.code, 200)
        self.assertEqual(response.body.decode(), 'OK')

    def test_root_post_method(self):
        response = self.fetch("/", method="POST", body='{"k": "v"}')
        self.assertEqual(response.code, 200)
        self.assertEqual(response.body.decode(), 'OK')

那么选择在哪里初始化 AsyncIOMainLoop() 的真正方法是什么？

Answer 1

肯定是documentation 所说的第二个例子：

from tornado.platform.asyncio import AsyncIOMainLoop
import asyncio
AsyncIOMainLoop().install()
asyncio.get_event_loop().run_forever()

关键是必须先安装AsyncIOMainLoop，然后再告诉asyncio 运行循环。