[Libguestfs] [PATCH 3/3] RHEV: Cleanup volumes on unclean shutdown

[Matthew Booth]

On 08/06/10 16:24, Richard W.M. Jones wrote:
> On Tue, Jun 08, 2010 at 03:55:50PM +0100, Matthew Booth wrote:
>> Currently image files will be left on the export domain if a conversion fails.
>> It isn't possible to delete these through the RHEV UI, requiring an
>> administrator to clean them up manually.
>>
>> This change causes images to be written to a temporary directory on the export
>> domain, and moved to the correct location immediately before writing the OVF
>> file. It also removes this temporary directory automatically on unclean
>> shutdown. This means that a failed conversion shouldn't leave anything on the
>> export domain. Even if it does, for example because of a power failure, the
>> temporary files are clearly separated in their own directory.
>
> The patch is fairly confusing because of the use of NFSHelper, but I
> have two potential concerns:

NFSHelper is unfortunate. As is NFS...

> (a) I don't think Perl 'rename' function will work if the temporary
> directory is on a different filesystem from the final destination.
> You might be better off using the 'mv' shell command (possibly with
> suitable shell quoting) instead.

This is ok, because the temporary directory is explicitly created on the 
export storage domain, so it won't cross a filesystem boundary. I do 
this specifically to avoid an additional data copy.

+    my $root = "$mountdir/$domainuuid";

$root is the top level directory of the export storage domain. Because 
it's a subdirectory of $mountdir, it's on NFS.

+    unless (defined($tmpdir)) {
+        my $nfs = Sys::VirtV2V::Target::RHEV::NFSHelper->new(sub {
+            print tempdir("v2v.XXXXXXXX", DIR => $root);
+        });

The NFS helper creates a new temporary directory will the given template 
under $root, so is also on NFS. NFSHelper works with stdout, so it 
prints the result.

+        my $fromchild = $nfs->{fromchild};
+        ($tmpdir) = <$fromchild>;

$tmpdir is the first line of output from the child.

+        $nfs->check_exit();

check_exit() will die() with error output if there was any error.


> (b) Where is $tmpdir typically?  If it's on /tmp you might find you
> have limited space, eg. if /tmp is a ramdisk.  (We have the same
> problem in libguestfs, and people can override it by setting $TMPDIR).

See above. The location of tmpdir is chosen deliberately.

Matt
-- 
Matthew Booth, RHCA, RHCSS
Red Hat Engineering, Virtualisation Team

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