摘要：這是我重新復習的原因放棄了之前自己實現的全面擁抱的這個改動是非常大的而且閱讀的源碼可以發現其中大部分函數都支持了類型檢驗和返回值提示值得閱讀

__auth__ = "aleimu"
__doc__ = "學習tornado6.0+ 版本與python3.7+"

import time
import asyncio
import tornado.gen
import tornado.web
import tornado.ioloop
import tornado.httpserver  # tornado的HTTP服務器實現
from tornado.options import define, options
from tornado.httpclient import HTTPClient, AsyncHTTPClient
from requests import get

settings = {"debug": True}
url = "http://127.0.0.1:5000/"  # 這是另個服務,請求5s后返回結果


# RuntimeError: Cannot run the event loop while another loop is running
# 解釋:HTTPClient內部寫 loop.run_xxx，因為那是啟動event loop的命令，通常只再最最最外面用一次，之后的代碼都應假設 loop 已經在運轉了。
def synchronous_fetch(url):
    print("synchronous_fetch")
    try:
        http_client = HTTPClient()
        time.sleep(5)
        response = http_client.fetch(url)
        print(response.body)
    except Exception as e:
        print("Error: " + str(e))
        return str(e)
    http_client.close()
    return response.body


# 替代synchronous_fetch的同步請求,沒有內置loop.run_xxx
def synchronous_get(url):
    response = get(url)
    time.sleep(5)
    print("synchronous_fetch")
    return response.text


# 簡單的模擬異步操作,這里之后應該替換成各種異步庫的函數
async def sleep():
    print("start sleep")
    await asyncio.sleep(5)
    print("end sleep")


# 異步請求
async def asynchronous_fetch(url):
    http_client = AsyncHTTPClient()
    response = await http_client.fetch(url)
    print("asynchronous_fetch")
    return response.body


# 測試
class MainHandler(tornado.web.RequestHandler):
    def get(self):
        self.write("Hello, world:%s" % self.request.request_time())
        self.finish()
        print("not finish!")
        return


# 同步阻塞
class synchronous_fetcher(tornado.web.RequestHandler):
    def get(self):
        self.write("%s,%s" % (synchronous_fetch(url), self.request.request_time()))


# 同步阻塞
class synchronous_geter(tornado.web.RequestHandler):
    def get(self):
        self.write("%s,%s" % (synchronous_get(url), self.request.request_time()))


# 異步阻塞,我以為curl "127.0.0.1:8888/1" 總耗時希望為5s,可是是25s,看來異步沒搞好,以下的函數都是基于此改進的
class asynchronous_fetcher_1(tornado.web.RequestHandler):
    async def get(self):
        body = await asynchronous_fetch(url)
        for i in range(3):
            print("skip %s" % i)
            await tornado.gen.sleep(5)
        time.sleep(5)
        print("end request")
        self.write("%s,%s" % (body, self.request.request_time()))

# curl "127.0.0.1:8888/1"
# b"{
  "data": "123"
}
",25.026000022888184


# 異步阻塞,效果同上,這里只是證明 tornado.gen.sleep(5)和asyncio.sleep(5) 效果一致
class asynchronous_fetcher_2(tornado.web.RequestHandler):
    async def get(self):
        body = await asynchronous_fetch(url)  # 關注協程完成后返回的結果
        for i in range(3):
            print("skip %s" % i)
            await sleep()
        time.sleep(5)
        print("end request")
        self.write("%s,%s" % (body, self.request.request_time()))

# curl "127.0.0.1:8888/2"
# b"{
  "data": "123"
}
",25.039999961853027


# 異步非阻塞-將部分異步操作放入組中,實現loop管理
class asynchronous_fetcher_3(tornado.web.RequestHandler):
    async def get(self):
        body = await asynchronous_fetch(url)
        await asyncio.wait([sleep() for i in range(3)])
        print("end request")
        self.write("%s,%s" % (body, self.request.request_time()))

# curl "127.0.0.1:8888/3"
# b"{
  "data": "123"
}
",10.001000165939331

# 異步非阻塞-將所有異步操作放入組中,實現loop管理
class asynchronous_fetcher_4(tornado.web.RequestHandler):
    async def get(self):
        task_list = [sleep() for i in range(3)]
        task_list.append(asynchronous_fetch(url))
        body = await asyncio.wait(task_list)  # 將所有異步操作的結果返回,但是是無序的,要是需要返回結果的話解析起來比較麻煩
        print("end request:", body)
        # print(type(body), len(body),type(body[0]),len(body[0]),type(body[0]))
        self.write("%s,%s" % ([x.result() for x in body[0] if x.result() is not None][0],
                              self.request.request_time()))
# curl "127.0.0.1:8888/4"
# b"{
  "data": "123"
}
",5.006999969482422

def make_app():
    return tornado.web.Application([
        (r"/", MainHandler),
        (r"/1", asynchronous_fetcher_1),
        (r"/2", asynchronous_fetcher_2),
        (r"/3", asynchronous_fetcher_3),
        (r"/4", asynchronous_fetcher_4),
        (r"/5", synchronous_fetcher),
        (r"/6", synchronous_geter),

    ], **settings)


if __name__ == "__main__":
    print("server start!")
    app = make_app()
    server = tornado.httpserver.HTTPServer(app)
    server.bind(8888)
    server.start(1)  # forks one process per cpu,windows上無法fork,這里默認為1
    tornado.ioloop.IOLoop.current().start()

1.Tornado使用單線程事件循環,寫的不好,會阻塞的非常嚴重,比如synchronous_geter
2.flask+celery可以完成常見的異步任務
3.await語法只能出現在通過async修飾的函數中
4.可以看到tornado.gen.coroutine, tornado.concurrent.run_on_executor,tornado.web.asynchronous,tornado.gen.coroutine等這些裝飾器都不在經常使用了,都由async和await代替

https://zhuanlan.zhihu.com/p/27258289   # Python async/await入門指南
http://www.tornadoweb.org/en/stable/guide/intro.html    # 這個官網
https://www.osgeo.cn/tornado/guide/intro.html   #Tornado 1.0 - Tornado 6.0的更新說明,以及6.0版本的中文文檔,適合英語不好的人閱讀
https://www.osgeo.cn/tornado/releases/v5.0.0.html#  在Python 3上， IOLoop 總是包裝asyncio事件循環。

On Python 3, IOLoop is always a wrapper around the asyncio event loop.
這是我重新復習tornado的原因,tornado放棄了之前自己實現的tornado.ioloop,全面擁抱asyncio的event_loop.這個改動是非常大的,
而且閱讀tornado的源碼可以發現其中大部分函數都支持了類型檢驗,和返回值提示,值得閱讀.