We managed to solve the issue.   The problem was related to the wallet.   As far as I know there are 2 types of wallet. The first type can be used only on the machine where it was created. The second type can be used on multiple machines.   Our problem is that our wallet was of the first type.   During map reduce the wallet is distributed among mappers and so with this "non sharable" wallet the mappers (located on different machines) are not able to use it.   We had to create the wallet with the command:    mkstore -wrl "<wallet_folder>" -create Hope our solution will help someone else in the future.   Stefano ... View more