[pve-devel] [PATCH storage 1/2] rbd: improve handling of missing images

[Aaron Lauterer]

It can happen, that an RBD image isn't cleaned up 100%. Calling 'rbd ls
-l' will then show errors that it is not possible to open the image in
question:
```
rbd: error opening vm-103-disk-1: (2) No such file or directory
rbd: listing images failed: (2) No such file or directory
```

Originally we only showed the last error line which is too generic and
doesn't give a good hint what is actually wrong.

We can improve that by catching these specific errors and add the
problematic disk imageto the returned list with a size of '-1'.
This way, normal operation won't be affected by errors and users can
still see that there is a broken image.

When the 'rbd rm' command is used on such an image, it will clean up
whatever is still left.
But for that to work, we also need to handle these errors in the
'rbd_ls_snap' sub as it is called from 'free_image'.

Signed-off-by: Aaron Lauterer <a.lauterer at proxmox.com>
---

Instead of parsing the error, we could have also ignored these specific
errors and run 'rbd ls' (without -l) a second time and compare the
outputs as the non -l variant will list the broken image as well.
But then we need to run a potentially expensive command twice.

Not sure if the way I parse the errors and handle the decision if we
have an error on which we should die ($show_err) is the most elegant
way.

 PVE/Storage/RBDPlugin.pm | 52 +++++++++++++++++++++++++++++++++++-----
 1 file changed, 46 insertions(+), 6 deletions(-)

diff --git a/PVE/Storage/RBDPlugin.pm b/PVE/Storage/RBDPlugin.pm
index 9047504..60fd353 100644
--- a/PVE/Storage/RBDPlugin.pm
+++ b/PVE/Storage/RBDPlugin.pm
@@ -168,6 +168,8 @@ my $krbd_feature_update = sub {
     }
 };
 
+my $missing_image_err_regex = '((?:vm|base)-\d+-.*): \(2\) No such file or directory$';
+
 sub run_rbd_command {
     my ($cmd, %args) = @_;
 
@@ -206,13 +208,28 @@ sub rbd_ls {
     my $raw = '';
     my $parser = sub { $raw .= shift };
 
+    my $show_err = 1;
+    my $missing_images = {};
+    my $err_parser = sub {
+	my $line = shift;
+	if ($line =~ m/$missing_image_err_regex/) {
+	    $show_err = 0;
+	    $missing_images->{$1} = 1;
+	} elsif ($line ne "rbd: listing images failed: (2) No such file or directory") {
+	    # this generic error is shown after the image specific "No such file..." one,
+	    # ignore it but not other errors
+	    $show_err = 1;
+	    die $line;
+	}
+    };
+
     my $cmd = $rbd_cmd->($scfg, $storeid, 'ls', '-l', '--format', 'json');
     eval {
-	run_rbd_command($cmd, errmsg => "rbd error", errfunc => sub {}, outfunc => $parser);
+	run_rbd_command($cmd, errmsg => "rbd error", errfunc => $err_parser, outfunc => $parser);
     };
     my $err = $@;
 
-    die $err if $err && $err !~ m/doesn't contain rbd images/ ;
+    die $err if $err && $show_err && $err !~ m/doesn't contain rbd images/ ;
 
     my $result;
     if ($raw eq '') {
@@ -223,6 +240,13 @@ sub rbd_ls {
 	die "got unexpected data from rbd ls: '$raw'\n";
     }
 
+    for my $image (keys %$missing_images) {
+	push @$result, {
+	    image => $image,
+	    size => -1,
+	};
+    }
+
     my $list = {};
 
     foreach my $el (@$result) {
@@ -250,7 +274,20 @@ sub rbd_ls_snap {
     my $cmd = $rbd_cmd->($scfg, $storeid, 'snap', 'ls', $name, '--format', 'json');
 
     my $raw = '';
-    run_rbd_command($cmd, errmsg => "rbd error", errfunc => sub {}, outfunc => sub { $raw .= shift; });
+    my $show_err = 0;
+    my $err_parser = sub {
+	my $line = shift;
+	if ($line !~ m/$missing_image_err_regex/) {
+	    $show_err = 1;
+	    die $line;
+	}
+    };
+    eval {
+	run_rbd_command($cmd, errmsg => "rbd error", errfunc => $err_parser, outfunc => sub { $raw .= shift; });
+    };
+    my $err = $@;
+    die $err if $err && $show_err;
+    return {} if $err && !$show_err; # could not open image, probably missing
 
     my $list;
     if ($raw =~ m/^(\[.*\])$/s) { # untaint
@@ -594,10 +631,13 @@ sub free_image {
 
     $class->deactivate_volume($storeid, $scfg, $volname);
 
-    my $cmd = $rbd_cmd->($scfg, $storeid, 'snap', 'purge',  $name);
-    run_rbd_command($cmd, errmsg => "rbd snap purge '$name' error");
 
-    $cmd = $rbd_cmd->($scfg, $storeid, 'rm', $name);
+    if (keys %{$snaps}) {
+	my $cmd = $rbd_cmd->($scfg, $storeid, 'snap', 'purge',  $name);
+	run_rbd_command($cmd, errmsg => "rbd snap purge '$name' error");
+    }
+
+    my $cmd = $rbd_cmd->($scfg, $storeid, 'rm', $name);
     run_rbd_command($cmd, errmsg => "rbd rm '$name' error");
 
     return undef;
-- 
2.30.2