Re: GNU Parallel Bug Reports Job failure semantics

[Andreas Bernauer]

On 9/13/11 12:43, Ole Tange wrote:
> We could implement a probe to test which machines were up when
> starting. That way you only would have problems with hosts that went
> offline after starting:
>
>    cat .ssh/pre_sshloginfile | parallel -j0 ssh server.example.com echo
> server.example.com>  .ssh/sshloginfile
>
> But these would take time and slow down the first connection.

If you keep the first connection, you can reuse it for the second, 
without much slowdown. See settings ControlMaster and ControlPath in 
ssh_config(5). For example, I have the following settings in my .ssh/config:

Host *
ControlMaster auto
ControlPath ~/.ssh/address@hidden:%p

If I open an ssh session in one terminal, I can reuse that connection in 
another terminal.

This won't really solve the problem with hosts that went offline after 
starting, but you have this problem anyways (eg., during script 
execution on the remote host).

{On a side note, I'm afraid parallel gets too bloated with many features 
that could be handled by other tools; for example, this very problem 
could be remedied by the script mentioned above and adding the '-Nf' 
options to ssh. Maybe there should be a contrib section for parallel?}

Cheers,
Andreas.