when i run mongodump it fails after 2-3 seconds with the following error:
Failed: error getting collection names for database `testdb`: read tcp 127.0.0.1:27017: i/o timeout

netstat -nlp | grep mongod:
tcp 0 0 127.0.0.1:27017 0.0.0.0:* LISTEN 6402/mongod

tail /var/log/mongodb/mongod.log
2015-02-25T15:21:41.664-0800 I NETWORK [initandlisten] waiting for connections on port 27017
2015-02-25T15:22:10.800-0800 I NETWORK [initandlisten] connection accepted from 127.0.0.1:43515 #1 (1 connection now open)
2015-02-25T15:22:24.967-0800 I COMMAND [conn1] command testdb.$cmd command: listCollections { listCollections: 1, cursor:

} keyUpdates:0 writeConflicts:0 numYields:0 reslen:117 locks:{} 14165ms
2015-02-25T15:22:24.967-0800 I NETWORK [conn1] end connection 127.0.0.1:43515 (0 connections now open)

There are no other error messages which I can see.

When I connect to my db and run show collections the list takes 15 seconds to generate. There are approximately 50k collections in the database of 16GB size.

This is a database exported from mongodb 2.4.5 mongodump, imported with mongorestore v3.0rc9.