连接断开时龙卷风内存泄漏

Question

我有一个设置，其中将龙卷风用作工人的通行证。 Tornado接收到请求，该请求将请求发送给N个工作人员，汇总结果并将其发送回客户端。 一切正常，除非出于某种原因发生超时-然后我出现了内存泄漏。

我有一个类似于以下伪代码的设置：

workers = ["http://worker1.example.com:1234/",
           "http://worker2.example.com:1234/", 
           "http://worker3.example.com:1234/" ...]

class MyHandler(tornado.web.RequestHandler):
    @tornado.web.asynchronous
    def post(self):
        responses = []

        def __callback(response):
            responses.append(response)
            if len(responses) == len(workers):
                self._finish_req(responses)

        for url in workers:
            async_client = tornado.httpclient.AsyncHTTPClient()
            request = tornado.httpclient.HTTPRequest(url, method=self.request.method, body=body)
            async_client.fetch(request, __callback) 

    def _finish_req(self, responses):
        good_responses = [r for r in responses if not r.error]
        if not good_responses:
            raise tornado.web.HTTPError(500, "\n".join(str(r.error) for r in responses))
        results = aggregate_results(good_responses)
        self.set_header("Content-Type", "application/json")
        self.write(json.dumps(results))
        self.finish()

application = tornado.web.Application([
    (r"/", MyHandler),
])

if __name__ == "__main__":
    ##.. some locking code 
    application.listen()
    tornado.ioloop.IOLoop.instance().start()

我究竟做错了什么？ 内存泄漏来自哪里？

Answer 1

我不知道问题的根源，看来gc应该可以解决这个问题，但是您可以尝试两种方法。

第一种方法是简化一些引用（当RequestHandler完成时，似乎仍然有对responses引用）：

class MyHandler(tornado.web.RequestHandler):
    @tornado.web.asynchronous
    def post(self):
        self.responses = []

        for url in workers:
            async_client = tornado.httpclient.AsyncHTTPClient()
            request = tornado.httpclient.HTTPRequest(url, method=self.request.method, body=body)
            async_client.fetch(request, self._handle_worker_response) 

    def _handle_worker_response(self, response):
        self.responses.append(response)
        if len(self.responses) == len(workers):
            self._finish_req()

    def _finish_req(self):
        ....

如果这不起作用，则始终可以手动调用垃圾回收：

import gc
class MyHandler(tornado.web.RequestHandler):
    @tornado.web.asynchronous
    def post(self):
        ....

    def _finish_req(self):
        ....

    def on_connection_close(self):
        gc.collect()

Answer 2

代码看起来不错。 泄漏可能在龙卷风内部。

我只是偶然发现了这一行：

async_client = tornado.httpclient.AsyncHTTPClient()

您是否知道此构造函数中的实例化魔术？ 从文档：

"""
The constructor for this class is magic in several respects:  It actually
creates an instance of an implementation-specific subclass, and instances
are reused as a kind of pseudo-singleton (one per IOLoop).  The keyword
argument force_instance=True can be used to suppress this singleton
behavior.  Constructor arguments other than io_loop and force_instance
are deprecated.  The implementation subclass as well as arguments to
its constructor can be set with the static method configure()
"""

因此，实际上，您不需要在循环中执行此操作。 （另一方面，它应该不会造成任何伤害。）但是，您使用CurlAsyncHTTPClient还是SimpleAsyncHTTPClient是哪个实现？

如果是SimpleAsyncHTTPClient，请注意以下代码中的注释：

"""
This class has not been tested extensively in production and
should be considered somewhat experimental as of the release of
tornado 1.2. 
"""

您可以尝试切换到CurlAsyncHTTPClient。 或按照Nikolay Fominyh的建议，并跟踪对__callback（）的调用。