标签:body 异步 tornado self request python3.7 tornado6 asynchronous print
废话不多说,直接上代码
__auth__ = "aleimu" __doc__ = "学习tornado6.0+ 版本与python3.7+" import time import asyncio import tornado.gen import tornado.web import tornado.ioloop import tornado.httpserver # tornado的HTTP服务器实现 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/" # 这是另个服务,请求5s后返回结果 # RuntimeError: Cannot run the event loop while another loop is running # 解释:HTTPClient内部写 loop.run_xxx,因为那是启动event loop的命令,通常只再最最最外面用一次,之后的代码都应假设 loop 已经在运转了。 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的同步请求,没有内置loop.run_xxx def synchronous_get(url): response = get(url) time.sleep(5) print("synchronous_fetch") return response.text # 简单的模拟异步操作,这里之后应该替换成各种异步库的函数 async def sleep(): print("start sleep") await asyncio.sleep(5) print("end sleep") # 异步请求 async def asynchronous_fetch(url): http_client = AsyncHTTPClient() response = await http_client.fetch(url) print("asynchronous_fetch") return response.body # 测试 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())) # 异步阻塞,我以为curl "127.0.0.1:8888/1" 总耗时希望为5s,可是是25s,看来异步没搞好,以下的函数都是基于此改进的 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 # 异步阻塞,效果同上,这里只是证明 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) # 关注协程完成后返回的结果 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 # 异步非阻塞-将部分异步操作放入组中,实现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 # 异步非阻塞-将所有异步操作放入组中,实现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) # 将所有异步操作的结果返回,但是是无序的,要是需要返回结果的话解析起来比较麻烦 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上无法fork,这里默认为1 tornado.ioloop.IOLoop.current().start()
总结
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1.Tornado使用单线程事件循环,写的不好,会阻塞的非常严重,比如synchronous_geter 2.flask+celery可以完成常见的异步任务 3.await语法只能出现在通过async修饰的函数中 4.可以看到tornado.gen.coroutine, tornado.concurrent.run_on_executor,tornado.web.asynchronous,tornado.gen.coroutine等这些装饰器都不在经常使用了,都由async和await代替
参考文档:
https://zhuanlan.zhihu.com/p/27258289 # Python async/await入门指南 http://www.tornadoweb.org/en/stable/guide/intro.html # 这个官网 https://www.osgeo.cn/tornado/guide/intro.html #Tornado 1.0 - Tornado 6.0的更新说明,以及6.0版本的中文文档,适合英语不好的人阅读 https://www.osgeo.cn/tornado/releases/v5.0.0.html# 在Python 3上, IOLoop 总是包装asyncio事件循环。
On Python 3, IOLoop is always a wrapper around the asyncio event loop.
这是我重新复习tornado的原因,tornado放弃了之前自己实现的tornado.ioloop,全面拥抱asyncio的event_loop.这个改动是非常大的,
而且阅读tornado的源码可以发现其中大部分函数都支持了类型检验,和返回值提示,值得阅读.
标签:body,异步,tornado,self,request,python3.7,tornado6,asynchronous,print 来源: https://blog.csdn.net/weixin_39108368/article/details/90295675
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