摘要.
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`| | 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() |`
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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 |
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| | 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.
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