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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.vespa.hosted.provision.maintenance;
import ai.vespa.metrics.ConfigServerMetrics;
import com.yahoo.config.provision.Deployer;
import com.yahoo.config.provision.NodeResources;
import com.yahoo.config.provision.NodeType;
import com.yahoo.jdisc.Metric;
import com.yahoo.vespa.hosted.provision.Node;
import com.yahoo.vespa.hosted.provision.NodeList;
import com.yahoo.vespa.hosted.provision.NodeRepository;
import com.yahoo.vespa.hosted.provision.node.Agent;
import com.yahoo.vespa.hosted.provision.provisioning.HostCapacity;
import java.time.Duration;
/**
* @author bratseth
*/
public class Rebalancer extends NodeMover<Rebalancer.Move> {
static final Duration waitTimeAfterPreviousDeployment = Duration.ofMinutes(10);
private final Deployer deployer;
private final Metric metric;
public Rebalancer(Deployer deployer,
NodeRepository nodeRepository,
Metric metric,
Duration interval) {
super(deployer, nodeRepository, interval, metric, Move.empty());
this.deployer = deployer;
this.metric = metric;
}
@Override
protected double maintain() {
if ( ! nodeRepository().nodes().isWorking()) return 0.0;
if ( ! nodeRepository().zone().cloud().allowHostSharing()) return 1.0; // Re-balancing not necessary
if (nodeRepository().zone().environment().isTest()) return 1.0; // Short-lived deployments; no need to rebalance
if (nodeRepository().zone().system().isCd()) return 1.0; // CD tests assert on # of nodes, avoid re-balancing as it make tests unstable
// Work with an unlocked snapshot as this can take a long time and full consistency is not needed
NodeList allNodes = nodeRepository().nodes().list();
updateSkewMetric(allNodes);
if ( ! zoneIsStable(allNodes)) return 1.0;
findBestMove(allNodes).execute(true, Agent.Rebalancer, deployer, metric, nodeRepository());
return 1.0;
}
@Override
protected Move suggestedMove(Node node, Node fromHost, Node toHost, NodeList allNodes) {
HostCapacity capacity = new HostCapacity(allNodes, nodeRepository().resourcesCalculator());
double skewReductionAtFromHost = skewReductionByRemoving(node, fromHost, capacity);
double skewReductionAtToHost = skewReductionByAdding(node, toHost, capacity);
double netSkewReduction = skewReductionAtFromHost + skewReductionAtToHost;
return new Move(node, fromHost, toHost, netSkewReduction);
}
@Override
protected Move bestMoveOf(Move a, Move b) {
if (a.netSkewReduction >= b.netSkewReduction) return a;
return b;
}
/** We do this here rather than in MetricsReporter because it is expensive and frequent updates are unnecessary */
private void updateSkewMetric(NodeList allNodes) {
HostCapacity capacity = new HostCapacity(allNodes, nodeRepository().resourcesCalculator());
double totalSkew = 0;
int hostCount = 0;
for (Node host : allNodes.nodeType(NodeType.host).state(Node.State.active)) {
hostCount++;
totalSkew += Node.skew(host.flavor().resources(), capacity.unusedCapacityOf(host));
}
metric.set(ConfigServerMetrics.HOSTED_VESPA_DOCKER_SKEW.baseName(),totalSkew/hostCount, null);
}
private double skewReductionByRemoving(Node node, Node fromHost, HostCapacity capacity) {
NodeResources freeHostCapacity = capacity.unusedCapacityOf(fromHost).justNumbers();
double skewBefore = Node.skew(fromHost.flavor().resources(), freeHostCapacity);
double skewAfter = Node.skew(fromHost.flavor().resources(), freeHostCapacity.add(node.flavor().resources().justNumbers()));
return skewBefore - skewAfter;
}
private double skewReductionByAdding(Node node, Node toHost, HostCapacity capacity) {
NodeResources freeHostCapacity = capacity.unusedCapacityOf(toHost).justNumbers();
double skewBefore = Node.skew(toHost.flavor().resources(), freeHostCapacity);
double skewAfter = Node.skew(toHost.flavor().resources(), freeHostCapacity.subtract(node.resources().justNumbers()));
return skewBefore - skewAfter;
}
static class Move extends MaintenanceDeployment.Move {
final double netSkewReduction;
Move(Node node, Node fromHost, Node toHost, double netSkewReduction) {
super(node, fromHost, toHost);
this.netSkewReduction = netSkewReduction;
}
@Override
public String toString() {
if (isEmpty()) return "move none";
return super.toString() + " [skew reduction " + netSkewReduction + "]";
}
public static Move empty() {
return new Move(null, null, null, 0);
}
}
}
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