RDB Loader: add support for SSH tunnels

[chuwy]

Migrated from snowplow/snowplow#3280

[alexanderdean]

High priority as without this we have to revert to running RDB Loader from a local box.

[ungn]

I had started to make a first stab at this for operations-server using the JSch java library.

Assuming you parse the ssh-tunnel config file like we do in our scripts, you should be able to connect using something like the following: (based on their port forwarding example here)

import com.jcraft.jsch.*;
...
JSch jsch=new JSch();
jsch.addIdentity(${keyfile_path});
Session session=jsch.getSession(${bastion_user}, ${bastion_host}, ${bastion_port});
session.connect();
session.setPortForwardingL(${local_database_port}, ${database_host}, ${remote_database_port});

This is untested though!

[alexanderdean]

Opens interesting questions about where/how to store the SSH key safely...

[jbeemster]

AWS Parameter Store can keep up to 4096 bytes which should fit a Private Key with a bit of headroom. This value can be encrypted using the AWS Key Management Service so could be a viable option for this...

http://docs.aws.amazon.com/systems-manager/latest/APIReference/API_Parameter.html