[pve-devel] [PATCH manager] Fix #2476: Fix auto-ballooning QMP command

[Stefan Reiter]

Commit 77123edbd0 (statd: refactor update_node_status) changed $target
in pvestatd's auto_balloning sub into a variable:

    my $target = int($res->{$vmid});

but then uses it in a string as a parameter to the $log function:

    $log->("BALLOON $vmid to $target (%d)\n", $target - $current);

This surprisingly causes the variable to be incorrectly converted into a
JSON string by perl's to_json (called in QMPClient after mon_cmd):

    {"value":"1234"}

instead of

    {"value":1234}

which causes QEMU to report the parameter as invalid:

    "Invalid parameter type for 'value', expected: integer"

This behaviour is made even trickier, since $target internally is still
considered more of an 'int' (although that's a weak claim in perl
anyway), showing up without quotes in Dumper et. al. - but the perldoc
for to_json scheds some light:

    simple scalars
        Simple Perl scalars (any scalar that is not a reference) are the
        most difficult objects to encode: this module will encode undefined
        scalars as JSON "null" values, scalars that have last been used in a
        string context before encoding as JSON strings, and anything else as
        number value

So coerce to_json to treat $target as an integer by using it as one and
everything is fine again.

Signed-off-by: Stefan Reiter <s.reiter at proxmox.com>
---

Also reported by multiple users in the forum, since auto-ballooning is
completely broken currently:

https://forum.proxmox.com/threads/host-instable-after-update-5-0-21-5.60404/

 PVE/Service/pvestatd.pm | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/PVE/Service/pvestatd.pm b/PVE/Service/pvestatd.pm
index 92d94809..b789b819 100755
--- a/PVE/Service/pvestatd.pm
+++ b/PVE/Service/pvestatd.pm
@@ -155,7 +155,7 @@ sub auto_balloning {
 	next if $target == $current; # no need to change
 
 	$log->("BALLOON $vmid to $target (%d)\n", $target - $current);
-	eval { PVE::QemuServer::Monitor::mon_cmd($vmid, "balloon", value => $target) };
+	eval { PVE::QemuServer::Monitor::mon_cmd($vmid, "balloon", value => int($target)) };
 	warn $@ if $@;
     }
 }
-- 
2.20.1