废话不多说,直接上代码
__auth__ = "aleimu"__doc__ = "学习tornado6.0+ 版本与python3.7+"import timeimport asyncioimport tornado.genimport tornado.webimport tornado.ioloopimport tornado.httpserver # tornado的HTTP服务器实现from tornado.options import define, optionsfrom tornado.httpclient import HTTPClient, AsyncHTTPClientfrom requests import getsettings = {'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_xxxdef 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',5.006999969482422def 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
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_geter2.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.