tornado6與python3.7 非同步新姿勢
摘要：
廢話不多說,直接上程式碼
__auth__ = "aleimu"
__doc__ = "學習tornado6.0+ 版本與python3.7+"
import time
import asyncio
import tornado.gen
import to...
廢話不多說,直接上程式碼
__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伺服器實現
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後返回結果
# 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，之後的程式碼都應假設 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,沒有內建loop.run_xxx
def synchronous_get(url):
response = get(url)
time.sleep(5)
print("synchronous_fetch")
return response.text
# 簡單的模擬非同步操作,這裡之後應該替換成各種非同步庫的函式
async def sleep():
print("start sleep")
await asyncio.sleep(5)
print("end sleep")
# 非同步請求
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()))
# 非同步阻塞,我以為curl "127.0.0.1:8888/1" 總耗時希望為5s,可是是25s,看來非同步沒搞好,以下的函式都是基於此改進的
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'{\n"data": "123"\n}\n',25.026000022888184
# 非同步阻塞,效果同上,這裡只是證明 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)# 關注協程完成後返回的結果
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'{\n"data": "123"\n}\n',25.039999961853027
# 非同步非阻塞-將部分非同步操作放入組中,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'{\n"data": "123"\n}\n',10.001000165939331
# 非同步非阻塞-將所有非同步操作放入組中,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)# 將所有非同步操作的結果返回,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'{\n"data": "123"\n}\n',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,這裡預設為1
tornado.ioloop.IOLoop.current().start()
總結
1.Tornado使用單執行緒事件迴圈,寫的不好,會阻塞的非常嚴重,比如synchronous_geter 2.flask+celery可以完成常見的非同步任務 3.await語法只能出現在通過async修飾的函式中 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
參考文件:
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版本的中文文件,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事件迴圈。
On Python 3, IOLoop is always a wrapper around the asyncio event loop.
這是我重新複習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的原始碼可以發現其中大部分函式都支援了型別檢驗,和返回值提示,值得閱讀.