许多并发的Cassandra数据库连接通过SSH隧道

我有一个应用程序使用PyCassa Cassandra客户端打开Cassandra服务器的许多并发连接。 当我在数据库服务器上本地运行客户端应用程序时，它工作。 但是，当我通过SSH通道转发到数据库服务器的Cassandra端口，并通过此隧道连接客户端应用程序到服务器时，几个连接通过，但通常我得到这样的错误：

'2012210105:49:49'|WARNING |_append_historyStorage|75 |Exception when appending to CassandraTimeSeries Traceback (most recent call last): File "atr/cassandratimeseries.py", line 140, in append cf = self._getColumnFamily(duration, 'main') File "atr/cassandratimeseries.py", line 63, in _getColumnFamily return ColumnFamily(ConnectionPool(self._keyspace, pool_timeout=100, timeout=15, max_overflow=5), self._columnFamilyName(duration, table_type), **self._column_family_op_options) File "/usr/local/lib/python2.7/dist-packages/pycassa/pool.py", line 356, in __init__ self.fill() File "/usr/local/lib/python2.7/dist-packages/pycassa/pool.py", line 415, in fill conn = self._create_connection() File "/usr/local/lib/python2.7/dist-packages/pycassa/pool.py", line 403, in _create_connection (exc.__class__.__name__, exc)) AllServersUnavailable: An attempt was made to connect to each of the servers twice, but none of the attempts succeeded. The last failure was TTransportException: TSocket read 0 bytes 

在我到服务器ssh'd的terminal打印一条消息，如：

 channel 1034: open failed: administratively prohibited: open failed channel 1035: open failed: administratively prohibited: open failed channel 1036: open failed: administratively prohibited: open failed channel 1037: open failed: administratively prohibited: open failed channel 1038: open failed: administratively prohibited: open failed channel 1039: open failed: administratively prohibited: open failed channel 1040: open failed: administratively prohibited: open failed 

有趣的是，如果我然后尝试SSH到服务器，我得到：

 channel 1023: chan_read_failed for istate 1 channel 1023: chan_write_failed for ostate 3 Shared connection to xx.xxx.xxx.xxx closed. 

如果我删除/ tmp中的主套接字文件，那么我可以ssh再次。

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任何想法可能会出错？ 我已经通过/etc/security/limits.conf为客户端和服务器增加了nofile限制（一万个）并重新启动。 “开放失败：行政禁止”表明存在一些行政限制。 这是什么，我该如何提高它（我应该怎么想出来呢？）

有没有其他的方式，SSH隧道比连接到本地端口更有限？

谢谢

 /* setup the channel layer */ if (!no_port_forwarding_flag && options.allow_tcp_forwarding) channel_permit_all_opens(); 

 AllowTcpForwarding yes