[Duplicity-talk] Progress feedback

[Michael Terry]

Now that machine-readable logging landed (thanks Ken!), I'd like to
turn my attention to machine-readable progress feedback.

I propose a two-fold approach:
1) Add periodic level 5 verbosity NOTICEs that say something like
"Processed 5M of files".  The machine-readable version would look
like:

NOTICE 2 5000\n
. Processed 5M of files\n
\n

The interesting difference there is the extra argument after the
message id.  It's a machine-readable version of the info in the
human-readable message.

The count would be against un-compressed size (i.e. on-disk size).

That would work for backing up.  When restoring, the situation is
reversed.  Duplicity must know how many volumes are on the other side.
 It could send notices like:

NOTICE 3 5000 1400\n
. . Processed 5M of 14M\n
\n

Because duplicity knows total and current count on restore.


2) Add a --dry-run option.  This would do normal activity, except
wouldn't tar/send data.  It would still emit the above notices.

When backing up, --dry-run and progress NOTICEs would allow a frontend
to first run duplicity with --dry-run and then know the total size of
processed files.  It would then run duplicity a second time without
--dry-run to do the actual backup.

It would be nice if the when backing up, duplicity could give us a
total, and we wouldn't have to do --dry-run, but I suppose it's not
worth it for duplicity to scan first itself just for the purpose of
getting a total count.


How does the above sound?  I'll code it, but I'm curious what Ken and
others have to say about the above design.

-mt