龙卷风：如何为多个请求共享pymongo连接？

Question

我想为多个请求共享一个MongoDB连接。 这就是我现在所拥有的，但看起来它正在为每个请求创建一个新连接。

dbasync = asyncmongo.Client(pool_id='mydb', host='127.0.0.1', port=27017, maxcached=10, maxconnections=50, dbname='bench')

@route('/readAsync')
class ReadAllAsynchHandler(tornado.web.RequestHandler):
    @tornado.web.asynchronous
    def get(self):        
        print("getting sessions")
        dbasync["ss"].find({}, callback=self._on_response)

    def _on_response(self, response, error):
        print("on response: %s" % response)
        if error:
            raise tornado.web.HTTPError(500)
        self.finish(SS_TEMPLATE.generate(sessions=response))

使用1000个并发客户端进行基准测试时，我收到以下错误：

Traceback (most recent call last):
  File "/home/ubuntu/envs/myproj/local/lib/python2.7/site-packages/tornado/web.py", line 1115, in _stack_context_handle_exception
    raise_exc_info((type, value, traceback))
  File "/home/ubuntu/envs/myproj/local/lib/python2.7/site-packages/tornado/web.py", line 1298, in wrapper
    result = method(self, *args, **kwargs)
  File "bench.py", line 29, in get
    dbasync["ss"].find({}, callback=self._on_response)
  File "/home/ubuntu/envs/myproj/local/lib/python2.7/site-packages/asyncmongo/cursor.py", line 380, in find
    connection = self.__pool.connection()
  File "/home/ubuntu/envs/myproj/local/lib/python2.7/site-packages/asyncmongo/pool.py", line 116, in connection
    raise TooManyConnections("%d connections are already equal to the max: %d" % (self._connections, self._maxconnections))
TooManyConnections: 50 connections are already equal to the max: 50

DEBUG:root:dropping connection. connection pool (10) is full. maxcached 10

Answer 1

maxconnections参数不用于缓冲现有连接池重用的请求。 相反，它只是存在以确保，如果需要，您的应用程序将不会消耗无限量的资源。 有关此行为的更多讨论，请参阅https://github.com/bitly/asyncmongo/pull/45 。 此拉取请求似乎提供了您所需的行为。 您可以使用以下内容安装asyncmongo及其修订版：

pip install git+git://github.com/ceymard/asyncmongo.git@7a8e6f6f446d71f8fd4f17de48994c0b6bee72ee

或者，您可以在Tornado设置中的某个位置限制应用程序的并发连接数，或者通过nginx限制（请参阅HttpLimitConnModule）