Problem:
Connected to a mongod and queried collections in the config database. After bouncing the config dartabase, re-executing the same statements failed with

> db.chunks.find()
error: {
"$err" : "dbclient error communicating with server: 10.118.18.91:27900",
"code" : 10278
}
> exit

Reproduce:

• create a 2 shard system
• insert data into a collection
• shard the collection
• connect to the mongos and execute
  > use config
  > db.chunks.find()

• in shell, shutdown the config server and re-start
• back in the original shell, execute
  > db.chunks.find()
  error: {
  "$err" : "dbclient error communicating with server: 10.118.18.91:27900",
  "code" : 10278
  }

Workaround:

• exit the shell and start the shell again, statement then executes

Business case:

• reliability