Re: off-box mirror-stream and friends

[Michael Neumann <mneumann@xxxxxxxx>]

Am Sun, 15 Feb 2009 21:38:54 -0800 (PST)
schrieb Matthew Dillon <dillon@apollo.backplane.com>:

> :I have what appears to be a 'Catch 22', wherein:
> :
> :hammer mirror-stream /master <user>@<remote_IP>:/new_slave
> :
> :returns:
> :
> :PFS slave /new-slave does not exist.
> :Do you want to create a new slave PFS? (yes|no) No terminal for
> response :Aborting operation
> :validate_mrec_header: short read
> :
> :'No terminal for response'  .was ass u me ed to be a byproduct of
> comign :in off an Xfce4-terminal (Xorg & Xfce4 are quite happy on
> 2.3.0, BTW) :
> :Dropped back out to the raw tty0 console and tried it from there.
> :
> :No joy.
> 
>     Definitely a bug in the hammer utility, I'm not sure there is 
>     anything I can do about it though because the remote ssh
> connection has no channel to accept a Y or N answer... stdin and
> stdout are used for the protocol stream and I think stderr is output
> only.
> 
>     In anycase, I think what this means is that this feature currently
>     only works if the slave is local (non-ssh connection).  So you
>     would be able to do it with <remote_master> <local_slave>.

Hm, I remember that we implemented this feature (auto-creation of
slaves) so that it can operate over ssh. And IIRC, it once worked 
for me using ssh (I am not sure if this was a remote machine or not).
Does this mean, it is broken?

> :Command *appear* to succeed if/as/when I *manually* create
> 'new_slave' :in advance with a matching shared_uuid. A local
> mirror-copy to it :suceeds, with new_slave showing the files mirrored.
> :
> :However, while the -vvv flag gives 5-sec updates, they all show a
> newer :starting point that pfs-status has for the target, and the
> contents of :the slave never change.
> 
>     You must access the slave via its softlink to get the latest
> version synced from the master.  If you try to access the slave via a
> null-mount you will be accessing a snapshot of the slave, not the
> current state of the slave.  The null mount locks in the transaction
> id of the slave.
> 
> :By way of contrast, mirror-stream between on-box master and on-box
> slave :  - same command otherwise - works fine.  No chdir needed to
> see the :updates, just a 'View, Reload' in thunar and sputniks.
> 
>     You are probably accessing it via the softlink, yes?  The gui is
>     probably using an absolute path.  If you were to CD into a
> sub-directory (even through the softlink), you would be accessing a
> snapshot as-of when you did the CD, not the latest synced copy.
> 
> :Query: Can the loop that seeks a 'yes' be changed to a 5-second 
> :countdown-timer with a message such as:
> :
> :Creating <new_slave> Hit Ctrl-c to abort
> :
> :.absent which it JFDI.
> :
> :Thanks,
> :
> :Bill Hacker
> 
>     That won't work, the target over an ssh link has no tty channel.
> 
>     Adding an option to create the slave automatically and passing it
> to the target hammer utility when it is run via the ssh, so it never
> has to ask at all, would work.  If someone would like to do that and
> submit a patch, I don't think it would take more then 20 minutes of
>     programming.

You mean, something like a -f (force) option? Should be damn easy to 
implement. I can do that, once I sit in front of a real computer
(with DragonFly) again :)

Regards,

  Michael