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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.vespa.hosted.provision.autoscale;
import com.yahoo.config.provision.ClusterResources;
import com.yahoo.config.provision.NodeResources;
import com.yahoo.vespa.hosted.provision.NodeList;
import com.yahoo.vespa.hosted.provision.NodeRepository;
import java.util.Optional;
/**
* A searcher of the space of possible allocation
*
* @author bratseth
*/
public class AllocationOptimizer {
// The min and max nodes to consider when not using application supplied limits
private static final int minimumNodes = 2; // Since this number includes redundancy it cannot be lower than 2
private static final int maximumNodes = 150;
private final NodeRepository nodeRepository;
public AllocationOptimizer(NodeRepository nodeRepository) {
this.nodeRepository = nodeRepository;
}
/**
* Searches the space of possible allocations given a target
* and (optionally) cluster limits and returns the best alternative.
*
* @return the best allocation, if there are any possible legal allocations, fulfilling the target
* fully or partially, within the limits
*/
public Optional<AllocatableClusterResources> findBestAllocation(ResourceTarget target,
AllocatableClusterResources current,
ClusterModel clusterModel,
Limits limits) {
int minimumNodes = AllocationOptimizer.minimumNodes;
if (limits.isEmpty())
limits = Limits.of(new ClusterResources(minimumNodes, 1, NodeResources.unspecified()),
new ClusterResources(maximumNodes, maximumNodes, NodeResources.unspecified()));
else
limits = atLeast(minimumNodes, limits).fullySpecified(current.clusterSpec(), nodeRepository, clusterModel.application().id());
Optional<AllocatableClusterResources> bestAllocation = Optional.empty();
NodeList hosts = nodeRepository.nodes().list().hosts();
for (int groups = limits.min().groups(); groups <= limits.max().groups(); groups++) {
for (int nodes = limits.min().nodes(); nodes <= limits.max().nodes(); nodes++) {
if (nodes % groups != 0) continue;
ClusterResources next = new ClusterResources(nodes,
groups,
nodeResourcesWith(nodes, groups,
limits, target, current, clusterModel));
var allocatableResources = AllocatableClusterResources.from(next, current.clusterSpec(), limits,
hosts, nodeRepository);
if (allocatableResources.isEmpty()) continue;
if (bestAllocation.isEmpty() || allocatableResources.get().preferableTo(bestAllocation.get()))
bestAllocation = allocatableResources;
}
}
return bestAllocation;
}
/**
* For the observed load this instance is initialized with, returns the resources needed per node to be at
* ideal load given a target node count
*/
private NodeResources nodeResourcesWith(int nodes,
int groups,
Limits limits,
ResourceTarget target,
AllocatableClusterResources current,
ClusterModel clusterModel) {
var scaled = clusterModel.loadWith(nodes, groups)
.scaled(Load.one().divide(clusterModel.redundancyAdjustment()).scaled(target.resources()));
// Combine the scaled resource values computed here
// with the currently configured non-scaled values, given in the limits, if any
var nonScaled = limits.isEmpty() || limits.min().nodeResources().isUnspecified()
? current.advertisedResources().nodeResources()
: limits.min().nodeResources(); // min=max for non-scaled
return nonScaled.withVcpu(scaled.vcpu()).withMemoryGb(scaled.memoryGb()).withDiskGb(scaled.diskGb());
}
/** Returns a copy of the given limits where the minimum nodes are at least the given value when allowed */
private Limits atLeast(int min, Limits limits) {
if (limits.max().nodes() < min) return limits; // not allowed
return limits.withMin(limits.min().withNodes(Math.max(min, limits.min().nodes())));
}
}
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