Re: [PATCH ha-manager v3 35/40] implement automatic rebalancing

["Daniel Kral" <d.kral@proxmox.com>]

On Tue Mar 31, 2026 at 11:07 AM CEST, Michael Köppl wrote:
> On Mon Mar 30, 2026 at 4:30 PM CEST, Daniel Kral wrote:
>> diff --git a/src/PVE/HA/Usage.pm b/src/PVE/HA/Usage.pm
>> index 43feb041..659ab30a 100644
>> --- a/src/PVE/HA/Usage.pm
>> +++ b/src/PVE/HA/Usage.pm
>> @@ -60,6 +60,40 @@ sub remove_service_usage {
>>      die "implement in subclass";
>>  }
>>  
>> +sub calculate_node_imbalance {
>> +    my ($self) = @_;
>> +
>> +    die "implement in subclass";
>> +}
>> +
>> +sub score_best_balancing_migrations {
>> +    my ($self, $migration_candidates, $limit) = @_;
>> +
>> +    die "implement in subclass";
>> +}
>> +
>> +sub select_best_balancing_migration {
>> +    my ($self, $migration_candidates) = @_;
>> +
>> +    my $migrations = $self->score_best_balancing_migrations($migration_candidates, 1);
>> +
>> +    return $migrations->[0];
>
> If an error occurs in the following call in
> score_best_balancing_migrations
>
>     my $migrations = eval {
>         $self->{scheduler}
>             ->score_best_balancing_migration_candidates_topsis($migration_candidates, $limit);
>     };
>
> you'd return an undefined $migrations, which would result in a
> dereference error here.
>

Hm, I can't seem to reproduce it even if I just `return undef` in
score_best_balancing_migrations{,_topsis}() and before writing this line
I tested it with:

    # cat perl-array-empty.pl
    #!/usr/bin/perl
    
    use v5.36;
    use Data::Dumper;
    
    my $array1 = undef;
    my $array2 = [];
    my $array3 = [{}];
    my $array4 = [{something => 'a'}, {else => 'b'}];
    
    my $i = 1;
    for my $var (($array1, $array2, $array3, $array4)) {
        print "array$i value: " . Dumper($var);
        print "array$i first: " . Dumper($var->[0]);
    
        $i++;
    }
    # ./perl-array-empty.pl
    array1 value: $VAR1 = undef;
    array1 first: $VAR1 = undef;
    array2 value: $VAR1 = [];
    array2 first: $VAR1 = undef;
    array3 value: $VAR1 = [
      {}
    ];
    array3 first: $VAR1 = {};
    array4 value: $VAR1 = [
      {
        'something' => 'a'
      },
      {
        'else' => 'b'
      }
    ];
    array4 first: $VAR1 = {
      'something' => 'a'
    };

Or do you have another reproducer for this?

>> +}
>> +
>> +sub score_best_balancing_migrations_topsis {
>> +    my ($self, $migration_candidates, $limit) = @_;
>> +
>> +    die "implement in subclass";
>> +}
>> +
>> +sub select_best_balancing_migration_topsis {
>> +    my ($self, $migration_candidates) = @_;
>> +
>> +    my $migrations = $self->score_best_balancing_migrations_topsis($migration_candidates, 1);
>> +
>> +    return $migrations->[0];
>> +}
>> +
>>  # Returns a hash with $nodename => $score pairs. A lower $score is better.
>>  sub score_nodes_to_start_service {
>>      my ($self, $sid) = @_;
>> diff --git a/src/PVE/HA/Usage/Dynamic.pm b/src/PVE/HA/Usage/Dynamic.pm
>> index 24c85a41..76d0feaa 100644
>> --- a/src/PVE/HA/Usage/Dynamic.pm
>> +++ b/src/PVE/HA/Usage/Dynamic.pm
>> @@ -104,6 +104,39 @@ sub remove_service_usage {
>>      $self->{haenv}->log('warning', "unable to remove service '$sid' usage - $@") if $@;
>>  }
>>  
>
> [snip]