教土豆学计算机
Tornado is a Python web framework and asynchronous networking library, originally developed at FriendFeed; ideal for long polling, WebSockets, and other applications that require a long-lived connection to each user.
Tornado 是一个 Python Web 框架, 同时也是一个异步网络库. Tornado 适用于 Long polling, WebSockets 以及需要长连接的场景.
Tornado can be roughly divided into four major components:
A web framework (including RequestHandler which is sub-classed to create web applications, and various supporting classes).
Client- and server-side implementations of HTTP (HTTPServer and AsyncHTTPClient).
An asynchronous networking library including the classes IOLoop and IOStream, which serve as the building blocks for the HTTP components and can also be used to implement other protocols.
A coroutine library (tornado.gen) which allows asynchronous code to be written in a more straightforward way than chaining callbacks.
To minimize the cost of concurrent connections, Tornado uses a single-threaded event loop.
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There are many styles of asynchronous interfaces
Callback argument
Return a placeholder (Future, Promise, Deferred)
Deliver to a queue
Callback registry (e.g. POSIX signals)
Coroutines are the recommended way to write asynchronous code in Tornado. Coroutines use the Python yield keyword to suspend and resume execution instead of a chain of callbacks
Here is a highly simplified version of the coroutine decorator’s inner loop
# Simplified inner loop of tornado.gen.Runner
def run(self):
# send(x) makes the current yield return x.
# It returns when the next yield is reached
future = self.gen.send(self.next)
def callback(f):
self.next = f.result()
self.run()
future.add_done_callback(callback)