tornado版本及多线程情况梳理

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python2.6 tornado-4.2-py26环境

import tornado.ioloopimport tornado.webfrom tornado.web import asynchronousfrom concurrent import futures executor = futures.ThreadPoolExecutor(max_workers=2)def call(handler):    handler.write("Hello, World!")    handler.finish() # 如果不写这行则回挂住class MainHandler(tornado.web.RequestHandler):        @asynchronous    def get(self):        executor.submit(call, self)def make_app():    return tornado.web.Application([        (r"/", MainHandler),    ])  if __name__ == "__main__":    app = make_app()    app.listen(9090)    tornado.ioloop.IOLoop.current().start()~

如果get/post返回future/gen（异步, yield的生成器）, 则需申明asynchronous, 不然该future不会加入IOLoop的事件, 直接处理完成, 如果在线程/协程中再有finish调用, 则会出现finish() called twice, 下面会详细说到。反过来说如果申明是asynchronous, 必需返回future 或者 gen

finish() call twice 示例代码：需注意线程抛的异常，主线程是catch不到的

import tornado.ioloopimport tornado.webfrom tornado.web import asynchronousfrom concurrent import futures executor = futures.ThreadPoolExecutor(max_workers=2)import timeimport tracebackdef call(handler):    try:         print id(handler)         handler.write("Hello, World! id: %s" % id(handler))         time.sleep(5)         handler.finish()         print "over.id[%s]" % id(handler)    except:        print traceback.format_exc()class MainHandler(tornado.web.RequestHandler):        #@asynchronous    def get(self):        executor.submit(call, self)def make_app():    return tornado.web.Application([        (r"/", MainHandler),    ])  if __name__ == "__main__":    app = make_app()    app.listen(9090)    tornado.ioloop.IOLoop.current().start()

另外注意如果使用tornado.ioloop.IOLoop.instance().add_callback(lambda: handler.finish({"xx": "yy"})) 返回值最好是字符串, 编码如果出现问题，则用户不会调用到finish，源码如下：

    def write(self, chunk):                if self._finished:            raise RuntimeError("Cannot write() after finish()")        if not isinstance(chunk, (bytes, unicode_type, dict)):            message = "write() only accepts bytes, unicode, and dict objects"            if isinstance(chunk, list):                message += ". Lists not accepted for security reasons; see http://www.tornadoweb.org/en/stable/web.html#tornado.web.RequestHandler.write"            raise TypeError(message)        if isinstance(chunk, dict):            chunk = escape.json_encode(chunk)  # 这里会报 'utf8' codec can't decode bytes            self.set_header("Content-Type", "application/json; charset=UTF-8")        chunk = utf8(chunk)        self._write_buffer.append(chunk)

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