[pve-devel] [PATCH pve-manager] POC: migrate_all: add auto best target selection

[Alexandre Derumier]

This is a POC, trying to implement basic loadbalancing
with best fist algorithm using dotproduct heuristic

some docs about dotproduct heuristic:
https://www.thinkmind.org/download.php?articleid=icn_2014_11_10_30065
https://hal.archives-ouvertes.fr/hal-00868016v2/document

The main idea is to ordering nodes with a weight, compute with
multidimentional vector from node + host (currently cpu,mem. But we could add network usage)

I have implemented in in migrate_all for the test, but It could
be used too in HA manager, to select best node.
(priority and groups can be added too easily)

and maybe implement a loadbalancer feature. (Maybe something
simple like migrate vm when memory/cpu are bigger than an defined threshold)

Signed-off-by: Alexandre Derumier <aderumier at odiso.com>
---
 PVE/API2/Nodes.pm | 66 ++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 59 insertions(+), 7 deletions(-)

diff --git a/PVE/API2/Nodes.pm b/PVE/API2/Nodes.pm
index 9e731e05..303a7ffb 100644
--- a/PVE/API2/Nodes.pm
+++ b/PVE/API2/Nodes.pm
@@ -1,5 +1,4 @@
 package PVE::API2::Nodes::Nodeinfo;
-
 use strict;
 use warnings;
 use POSIX qw(LONG_MAX);
@@ -1921,7 +1920,11 @@ __PACKAGE__->register_method ({
 	additionalProperties => 0,
 	properties => {
 	    node => get_standard_option('pve-node'),
-            target => get_standard_option('pve-node', { description => "Target node." }),
+	    target => {
+		description => "Target node.",
+		type => 'string',  format => 'pve-node',
+		optional => 1,
+	    },
             maxworkers => {
                 description => "Maximal number of parallel migration job." .
 		    " If not set use 'max_workers' from datacenter.cfg," .
@@ -1950,27 +1953,68 @@ __PACKAGE__->register_method ({
 	$nodename = PVE::INotify::nodename() if $nodename eq 'localhost';
 
 	my $target = $param->{target};
-	raise_param_exc({ target => "target is local node."}) if $target eq $nodename;
+	raise_param_exc({ target => "target is local node."}) if $target && $target eq $nodename;
 
 	PVE::Cluster::check_cfs_quorum();
 
-	PVE::Cluster::check_node_exists($target);
+	PVE::Cluster::check_node_exists($target) if $target;
 
 	my $datacenterconfig = cfs_read_file('datacenter.cfg');
 	# prefer parameter over datacenter cfg settings
-	my $maxWorkers = $param->{maxworkers} || $datacenterconfig->{max_workers} ||
-	    die "either 'maxworkers' parameter or max_workers in datacenter.cfg must be set!\n";
+	my $maxWorkers = 1;
+	$maxWorkers = $param->{maxworkers} || $datacenterconfig->{max_workers} ||
+	    die "either 'maxworkers' parameter or max_workers in datacenter.cfg must be set!\n" if $target;
 
 	my $code = sub {
 	    $rpcenv->{type} = 'priv'; # to start tasks in background
 
 	    my $vmlist = &$get_filtered_vmlist($nodename, $param->{vms}, 1, 1);
-
 	    my $workers = {};
 	    foreach my $vmid (sort keys %$vmlist) {
 		my $d = $vmlist->{$vmid};
+
+		if(!$target) {
+		
+		    my $members = PVE::Cluster::get_members();
+		    my $rrd = PVE::Cluster::rrd_dump();
+		    my $nodelist = PVE::Cluster::get_nodelist();
+
+		    my $vm_stats = PVE::API2Tools::extract_vm_stats($vmid, $d, $rrd);
+		    my $vm_cpu = $vm_stats->{cpu} * $vm_stats->{maxcpu};
+		    my $vm_mem = $vm_stats->{mem};
+		    my @vec_vm = ($vm_cpu, $vm_mem);  #? add network usage dimension ?
+
+		    my $nodes_weight = {};
+		    my $highest_weight = 0;
+		    foreach my $node (@$nodelist) {
+			next if $node eq $nodename;
+
+			my $node_stats = PVE::API2Tools::extract_node_stats($node, $members, $rrd);
+			my $node_freemem = $node_stats->{maxmem} - $node_stats->{mem};
+			my $node_freecpu = (100 - $node_stats->{cpu}) * $node_stats->{maxcpu};  #how to handle different cpu model power ? bogomips ?
+			next if $node_stats->{status} ne 'online';
+			next if $node_freecpu < $vm_cpu;
+			next if $node_freemem < $vm_mem;
+			next if $node_stats->{maxcpu} < $vm_stats->{maxcpu};
+			# fixme: check storage available
+			# fixme: check vmbr available
+
+			my @vec_node = ($node_freecpu, $node_freemem); #? add network usage dimension ?
+			my $weight = dotprod(\@vec_vm,\@vec_node);
+			$nodes_weight->{$weight} = $node;
+			$highest_weight = $weight if $weight > $highest_weight;
+		    }	
+		    $target = $nodes_weight->{$highest_weight};	
+		    if(!$target) {
+			warn "couldn't find a target for vmid $vmid\n";
+			next;
+		    }
+		    print "vm:$vmid best target:$target\n";
+		}
+
 		my $pid;
 		eval { $pid = &$create_migrate_worker($nodename, $d->{type}, $vmid, $target); };
+		$target = $param->{target};
 		warn $@ if $@;
 		next if !$pid;
 
@@ -2086,6 +2130,14 @@ sub complete_templet_repo {
     return $res;
 }
 
+sub dotprod {
+    my ($vec_a, $vec_b) = @_;
+    die "they must have the same size\n" unless @$vec_a == @$vec_b;
+    my $sum = 0;
+    $sum += $vec_a->[$_] * $vec_b->[$_] for 0..$#$vec_a;
+    return $sum;
+}
+
 package PVE::API2::Nodes;
 
 use strict;
-- 
2.20.1