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Enable --progress-total option using pv. #547

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@kpoeppel kpoeppel commented Aug 2, 2023

Add a --progress-total option that internally runs btrbk diff first to get a total size to be transferred (per target). This option is an alternative to --progress and shows a ETA time estimate as well as progress bar via pv.

Aims to resolve #543 .

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Thanks for the MR, looks promising. I've had a brief look at it, and did not have time to test it yet (I'm quite busy at the moment, this might take a while sorry).

Do you have any numbers on how good are the estimates are and how long it takes to calculate the diffs? I'm especially curious as the btrfs send-stream adds quite some metadata.

btrbk Outdated
Comment on lines 723 to 725
my @cmd = ( "pv" );
push @cmd, ("-s", $total_len);
push @cmd, "-e -r -p -i 2";
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Did you check if mbuffer supports similar functionality? I'd hate to re-introduce pv as a new dependency, even if optional.

see 9dc717c

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mbuffer does not support this unfortunately.

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mbuffer without -q has a progress bar that runs by default that looks like this:

in @ 24.0 MiB/s, out @ 24.0 MiB/s, 4352 MiB total, buffer 100% full

Although, if pv has a progress bar that better shows up in log files, like when systemd is what manages btrbk, then that's a big plus.

btrbk Outdated
Comment on lines 5272 to 5299
sub sub_diff($$) {
#
# calc snapshot diff (btrfs find-new)
#
my $src_vol = $_[0];
my $target_vol = $_[1];

# NOTE: in some cases "cgen" differs from "gen", even for read-only snapshots (observed: gen=cgen+1)
my $lastgen = $src_vol->{node}{gen} + 1;

# dump files, sorted and unique
my $ret = btrfs_subvolume_find_new($target_vol, $lastgen);

INFO "Listing changed files for subvolume: $target_vol->{PRINT} (gen=$target_vol->{node}{gen})";
INFO "Starting at generation after subvolume: $src_vol->{PRINT} (gen=$src_vol->{node}{gen})";
INFO "Listing files modified within generation range: [$lastgen..$target_vol->{node}{gen}]";
DEBUG "Newest file generation (transid marker) was: $ret->{transid_marker}";
my $files = $ret->{files};
my $total_len = 0;
foreach my $name (sort keys %$files) {
my $finfo = $files->{$name};
$total_len += $finfo->{len};
}

INFO "Total size: " . print_size($total_len) ;

return $total_len;
}
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We could get similar (same? better?) results by using the results from btrbk extents, which might have some advantages:

  • faster (?) (note: installing module "IO::AIO" gives quite some speedup!)
  • has caching capabilities (!)

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It don't know, I haven't used btrbk extents so far. This is just a copy of the part run by btrbk diff

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Is this a must or still debatable?

@kpoeppel
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kpoeppel commented Aug 3, 2023

Thanks for the MR, looks promising. I've had a brief look at it, and did not have time to test it yet (I'm quite busy at the moment, this might take a while sorry).

Do you have any numbers on how good are the estimates are and how long it takes to calculate the diffs? I'm especially curious as the btrfs send-stream adds quite some metadata.

Speed-wise it was pretty fast / negligible compared to the transfer time for all my cases.

@kpoeppel
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kpoeppel commented Aug 3, 2023

Another general comment:
Handling the stderr output is not optimal in the current code, and I used a workaround to feed stderr of the subprocess directly to stderr of the main script. This way errors are not captured.
Maybe the chomp + readline combination should be replaced by something involving select. Also handling the stderr updates of pv or mbuffer (removing parts of their outputs over time) makes it difficult probably.

@digint digint force-pushed the master branch 6 times, most recently from 594fc6d to dac6350 Compare August 5, 2023 18:28
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Any update / further requests for the PR?

@tbertels
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tbertels commented Apr 19, 2024

I'd suggest updating the --progress entry:
--progress show progress bar on send-receive operation
There's no progress bar with --progress since the switch to mbuffer, just transferred size and speed.

A man entry should be added too.

Note that there wasn't any commit here since August 2023, so digint is probably busy.

It would be nice to show total progress even for the initial snapshot, at least if quotas are enabled (otherwise it can be pretty slow to compute for HDDs with lots of data).
sudo btrfs subvolume show [snapshot]
then displays the snapshot size.

Still, it's pretty useful already.

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Enable some time estimate for --progress option (or a new --progress-total) option.
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