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Implement the basic constraint based algorithm (#381)
Implement basic constraint algorithm: Greedy based, each time it picks the best scores given each replica and assigns the replica to the node. It doesn't guarantee to achieve global optimal but local optimal result The algorithm is based on a given set of constraints * HardConstraint: Approve or deny the assignment given its condition, any assignment cannot bypass any "hard constraint" * SoftConstraint: Evaluate the assignment by points/rewards/scores, a higher point means a better assignment The goal is to avoid all "hard constraints" while accumulating the most points(rewards) from "soft constraints"
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129 changes: 129 additions & 0 deletions
129
...va/org/apache/helix/controller/rebalancer/waged/constraints/ConstraintBasedAlgorithm.java
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| package org.apache.helix.controller.rebalancer.waged.constraints; | ||
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| /* | ||
| * Licensed to the Apache Software Foundation (ASF) under one | ||
| * or more contributor license agreements. See the NOTICE file | ||
| * distributed with this work for additional information | ||
| * regarding copyright ownership. The ASF licenses this file | ||
| * to you under the Apache License, Version 2.0 (the | ||
| * "License"); you may not use this file except in compliance | ||
| * with the License. You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, | ||
| * software distributed under the License is distributed on an | ||
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY | ||
| * KIND, either express or implied. See the License for the | ||
| * specific language governing permissions and limitations | ||
| * under the License. | ||
| */ | ||
|
|
||
| import java.util.ArrayList; | ||
| import java.util.Comparator; | ||
| import java.util.HashMap; | ||
| import java.util.List; | ||
| import java.util.Map; | ||
| import java.util.Optional; | ||
| import java.util.Set; | ||
| import java.util.function.Function; | ||
| import java.util.stream.Collectors; | ||
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| import org.apache.helix.HelixRebalanceException; | ||
| import org.apache.helix.controller.rebalancer.waged.RebalanceAlgorithm; | ||
| import org.apache.helix.controller.rebalancer.waged.model.AssignableNode; | ||
| import org.apache.helix.controller.rebalancer.waged.model.AssignableReplica; | ||
| import org.apache.helix.controller.rebalancer.waged.model.ClusterContext; | ||
| import org.apache.helix.controller.rebalancer.waged.model.ClusterModel; | ||
| import org.apache.helix.controller.rebalancer.waged.model.OptimalAssignment; | ||
| import org.slf4j.Logger; | ||
| import org.slf4j.LoggerFactory; | ||
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| import com.google.common.collect.Maps; | ||
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| /** | ||
| * The algorithm is based on a given set of constraints | ||
| * - HardConstraint: Approve or deny the assignment given its condition, any assignment cannot | ||
| * bypass any "hard constraint" | ||
| * - SoftConstraint: Evaluate the assignment by points/rewards/scores, a higher point means a better | ||
| * assignment | ||
| * The goal is to accumulate the most points(rewards) from "soft constraints" while avoiding any | ||
| * "hard constraints" | ||
| */ | ||
| class ConstraintBasedAlgorithm implements RebalanceAlgorithm { | ||
| private static final Logger LOG = LoggerFactory.getLogger(ConstraintBasedAlgorithm.class); | ||
| private final List<HardConstraint> _hardConstraints; | ||
| private final List<SoftConstraint> _softConstraints; | ||
| private final SoftConstraintWeightModel _softConstraintsWeightModel; | ||
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| ConstraintBasedAlgorithm(List<HardConstraint> hardConstraints, | ||
| List<SoftConstraint> softConstraints, SoftConstraintWeightModel softConstraintWeightModel) { | ||
| _hardConstraints = hardConstraints; | ||
| _softConstraints = softConstraints; | ||
| _softConstraintsWeightModel = softConstraintWeightModel; | ||
| } | ||
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| @Override | ||
| public OptimalAssignment calculate(ClusterModel clusterModel) throws HelixRebalanceException { | ||
| OptimalAssignment optimalAssignment = new OptimalAssignment(); | ||
| Map<String, Set<AssignableReplica>> replicasByResource = clusterModel.getAssignableReplicaMap(); | ||
| List<AssignableNode> nodes = new ArrayList<>(clusterModel.getAssignableNodes().values()); | ||
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| // TODO: different orders of resource/replica could lead to different greedy assignments, will | ||
| // revisit and improve the performance | ||
| for (String resource : replicasByResource.keySet()) { | ||
| for (AssignableReplica replica : replicasByResource.get(resource)) { | ||
| Optional<AssignableNode> maybeBestNode = | ||
| getNodeWithHighestPoints(replica, nodes, clusterModel.getContext(), optimalAssignment); | ||
| // stop immediately if any replica cannot find best assignable node | ||
| if (optimalAssignment.hasAnyFailure()) { | ||
| String errorMessage = String.format( | ||
| "Unable to find any available candidate node for partition %s; Fail reasons: %s", | ||
| replica.getPartitionName(), optimalAssignment.getFailures()); | ||
| throw new HelixRebalanceException(errorMessage, | ||
| HelixRebalanceException.Type.FAILED_TO_CALCULATE); | ||
| } | ||
| maybeBestNode.ifPresent(node -> clusterModel.assign(replica.getResourceName(), | ||
| replica.getPartitionName(), replica.getReplicaState(), node.getInstanceName())); | ||
| } | ||
| } | ||
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| return optimalAssignment.convertFrom(clusterModel); | ||
| } | ||
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| private Optional<AssignableNode> getNodeWithHighestPoints(AssignableReplica replica, | ||
| List<AssignableNode> assignableNodes, ClusterContext clusterContext, | ||
| OptimalAssignment optimalAssignment) { | ||
| Map<AssignableNode, List<HardConstraint>> hardConstraintFailures = new HashMap<>(); | ||
| List<AssignableNode> candidateNodes = assignableNodes.stream().filter(candidateNode -> { | ||
| boolean isValid = true; | ||
| // need to record all the failure reasons and it gives us the ability to debug/fix the runtime | ||
| // cluster environment | ||
| for (HardConstraint hardConstraint : _hardConstraints) { | ||
| if (!hardConstraint.isAssignmentValid(candidateNode, replica, clusterContext)) { | ||
| hardConstraintFailures.computeIfAbsent(candidateNode, node -> new ArrayList<>()) | ||
| .add(hardConstraint); | ||
| isValid = false; | ||
| } | ||
| } | ||
| return isValid; | ||
| }).collect(Collectors.toList()); | ||
| if (candidateNodes.isEmpty()) { | ||
| optimalAssignment.recordAssignmentFailure(replica, | ||
| Maps.transformValues(hardConstraintFailures, this::convertFailureReasons)); | ||
| return Optional.empty(); | ||
| } | ||
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| Function<AssignableNode, Float> calculatePoints = | ||
| (candidateNode) -> _softConstraintsWeightModel.getSumOfScores(_softConstraints.stream() | ||
| .collect(Collectors.toMap(Function.identity(), softConstraint -> softConstraint | ||
| .getAssignmentOriginScore(candidateNode, replica, clusterContext)))); | ||
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| return candidateNodes.stream().max(Comparator.comparing(calculatePoints)); | ||
| } | ||
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| private List<String> convertFailureReasons(List<HardConstraint> hardConstraints) { | ||
| return hardConstraints.stream().map(HardConstraint::getDescription) | ||
| .collect(Collectors.toList()); | ||
| } | ||
| } |
41 changes: 41 additions & 0 deletions
41
...apache/helix/controller/rebalancer/waged/constraints/ConstraintBasedAlgorithmFactory.java
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,41 @@ | ||
| package org.apache.helix.controller.rebalancer.waged.constraints; | ||
|
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| /* | ||
| * Licensed to the Apache Software Foundation (ASF) under one | ||
| * or more contributor license agreements. See the NOTICE file | ||
| * distributed with this work for additional information | ||
| * regarding copyright ownership. The ASF licenses this file | ||
| * to you under the Apache License, Version 2.0 (the | ||
| * "License"); you may not use this file except in compliance | ||
| * with the License. You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, | ||
| * software distributed under the License is distributed on an | ||
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY | ||
| * KIND, either express or implied. See the License for the | ||
| * specific language governing permissions and limitations | ||
| * under the License. | ||
| */ | ||
|
|
||
| import java.util.ArrayList; | ||
| import java.util.List; | ||
|
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| import org.apache.helix.controller.rebalancer.waged.RebalanceAlgorithm; | ||
| import org.apache.helix.model.ClusterConfig; | ||
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| public class ConstraintBasedAlgorithmFactory { | ||
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| // TODO: the parameter comes from cluster config, will tune how these 2 integers will change the | ||
| // soft constraint weight model | ||
| public static RebalanceAlgorithm getInstance() { | ||
| // TODO initialize constraints, depending on constraints implementations PRs | ||
| List<HardConstraint> hardConstraints = new ArrayList<>(); | ||
| List<SoftConstraint> softConstraints = new ArrayList<>(); | ||
| SoftConstraintWeightModel softConstraintWeightModel = new SoftConstraintWeightModel(); | ||
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| return new ConstraintBasedAlgorithm(hardConstraints, softConstraints, | ||
| softConstraintWeightModel); | ||
| } | ||
| } |
48 changes: 0 additions & 48 deletions
48
...g/apache/helix/controller/rebalancer/waged/constraints/ConstraintsRebalanceAlgorithm.java
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