Hi,

We have encountered an issue that mongos holding too many eventfd file handles while there are only few connections.  This mongos had crashed because the system was using out of file handles. Following are the logs at that time:

020-05-28T14:29:58.053+0800 F NETWORK [conn59705274] error in eventfd: Too many open files in system 
2020-05-28T14:29:58.053+0800 I NETWORK [listener] Error accepting new connection on 0.0.0.0:3027: Too many open files in system 
2020-05-28T14:29:58.053+0800 F - [conn59705274] Fatal Assertion 50833 at src/mongo/transport/baton_asio_linux.h 68

And after it restarted, we noticed that it still holding 200k file handles, most of which are of type eventfd. While there were only 6 opening connections. I have uploaded the FTDC data, mongos.log and the file handle list. Please help!