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Handle shard over allocation during partial zone/rack or independent …
…node failures (opensearch-project#1149) The changes ensure that in the event of a partial zone failure, the surviving nodes in the minority zone don't get overloaded with shards, this is governed by a skewness limit. Signed-off-by: Bukhtawar Khan <bukhtawa@amazon.com>
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...ava/org/opensearch/cluster/routing/allocation/decider/NodeLoadAwareAllocationDecider.java
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| /* | ||
| * SPDX-License-Identifier: Apache-2.0 | ||
| * | ||
| * The OpenSearch Contributors require contributions made to | ||
| * this file be licensed under the Apache-2.0 license or a | ||
| * compatible open source license. | ||
| */ | ||
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| package org.opensearch.cluster.routing.allocation.decider; | ||
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| import org.apache.logging.log4j.LogManager; | ||
| import org.apache.logging.log4j.Logger; | ||
| import org.apache.logging.log4j.message.ParameterizedMessage; | ||
| import org.opensearch.cluster.metadata.Metadata; | ||
| import org.opensearch.cluster.routing.RoutingNode; | ||
| import org.opensearch.cluster.routing.ShardRouting; | ||
| import org.opensearch.cluster.routing.allocation.RoutingAllocation; | ||
| import org.opensearch.common.settings.ClusterSettings; | ||
| import org.opensearch.common.settings.Setting; | ||
| import org.opensearch.common.settings.Settings; | ||
| import org.opensearch.common.settings.Setting.Property; | ||
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| import java.util.function.BiPredicate; | ||
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| /** | ||
| * This {@link NodeLoadAwareAllocationDecider} controls shard over-allocation | ||
| * due to node failures or otherwise on the surviving nodes. The allocation limits | ||
| * are decided by the user provisioned capacity, to determine if there were lost nodes. | ||
| * The provisioned capacity as defined by the below settings needs to be updated on every | ||
| * cluster scale up and scale down operations. | ||
| * <pre> | ||
| * cluster.routing.allocation.overload_awareness.provisioned_capacity: N | ||
| * </pre> | ||
| * <p> | ||
| * and prevent allocation on the surviving nodes of the under capacity cluster | ||
| * based on overload factor defined as a percentage by | ||
| * <pre> | ||
| * cluster.routing.allocation.load_awareness.skew_factor: X | ||
| * </pre> | ||
| * The total limit per node based on skew_factor doesn't limit primaries that previously | ||
| * existed on the disk as those shards are force allocated by | ||
| * {@link AllocationDeciders#canForceAllocatePrimary(ShardRouting, RoutingNode, RoutingAllocation)} | ||
| * however new primaries due to index creation, snapshot restore etc can be controlled via the below settings. | ||
| * Setting the value to true allows newly created primaries to get assigned while preventing the replica allocation | ||
| * breaching the skew factor. | ||
| * Note that setting this to false can result in the primaries not get assigned and the cluster turning RED | ||
| * <pre> | ||
| * cluster.routing.allocation.load_awareness.allow_unassigned_primaries | ||
| * </pre> | ||
| */ | ||
| public class NodeLoadAwareAllocationDecider extends AllocationDecider { | ||
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| public static final String NAME = "load_awareness"; | ||
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| public static final Setting<Integer> CLUSTER_ROUTING_ALLOCATION_LOAD_AWARENESS_PROVISIONED_CAPACITY_SETTING = | ||
| Setting.intSetting("cluster.routing.allocation.load_awareness.provisioned_capacity", -1, -1, | ||
| Property.Dynamic, Property.NodeScope); | ||
| public static final Setting<Double> CLUSTER_ROUTING_ALLOCATION_LOAD_AWARENESS_SKEW_FACTOR_SETTING = | ||
| Setting.doubleSetting("cluster.routing.allocation.load_awareness.skew_factor", 50, -1, Property.Dynamic, | ||
| Property.NodeScope); | ||
| public static final Setting<Boolean> CLUSTER_ROUTING_ALLOCATION_LOAD_AWARENESS_ALLOW_UNASSIGNED_PRIMARIES_SETTING = | ||
| Setting.boolSetting("cluster.routing.allocation.load_awareness.allow_unassigned_primaries", | ||
| true, Setting.Property.Dynamic, Property.NodeScope); | ||
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| private volatile int provisionedCapacity; | ||
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| private volatile double skewFactor; | ||
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| private volatile boolean allowUnassignedPrimaries; | ||
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| private static final Logger logger = LogManager.getLogger(NodeLoadAwareAllocationDecider.class); | ||
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| public NodeLoadAwareAllocationDecider(Settings settings, ClusterSettings clusterSettings) { | ||
| this.skewFactor = CLUSTER_ROUTING_ALLOCATION_LOAD_AWARENESS_SKEW_FACTOR_SETTING.get(settings); | ||
| this.provisionedCapacity = CLUSTER_ROUTING_ALLOCATION_LOAD_AWARENESS_PROVISIONED_CAPACITY_SETTING.get(settings); | ||
| this.allowUnassignedPrimaries = CLUSTER_ROUTING_ALLOCATION_LOAD_AWARENESS_ALLOW_UNASSIGNED_PRIMARIES_SETTING.get(settings); | ||
| clusterSettings.addSettingsUpdateConsumer(CLUSTER_ROUTING_ALLOCATION_LOAD_AWARENESS_SKEW_FACTOR_SETTING, | ||
| this::setSkewFactor); | ||
| clusterSettings.addSettingsUpdateConsumer(CLUSTER_ROUTING_ALLOCATION_LOAD_AWARENESS_PROVISIONED_CAPACITY_SETTING, | ||
| this::setProvisionedCapacity); | ||
| clusterSettings.addSettingsUpdateConsumer(CLUSTER_ROUTING_ALLOCATION_LOAD_AWARENESS_ALLOW_UNASSIGNED_PRIMARIES_SETTING, | ||
| this::setAllowUnassignedPrimaries); | ||
| } | ||
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| private void setAllowUnassignedPrimaries(boolean allowUnassignedPrimaries) { | ||
| this.allowUnassignedPrimaries = allowUnassignedPrimaries; | ||
| } | ||
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| private void setSkewFactor(double skewFactor) { | ||
| this.skewFactor = skewFactor; | ||
| } | ||
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| private void setProvisionedCapacity(int provisionedCapacity) { | ||
| this.provisionedCapacity = provisionedCapacity; | ||
| } | ||
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| @Override | ||
| public Decision canAllocate(ShardRouting shardRouting, RoutingNode node, RoutingAllocation allocation) { | ||
| return underCapacity(shardRouting, node, allocation, (count, limit) -> count >= limit); | ||
| } | ||
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| @Override | ||
| public Decision canRemain(ShardRouting shardRouting, RoutingNode node, RoutingAllocation allocation) { | ||
| return underCapacity(shardRouting, node, allocation, (count, limit) -> count > limit); | ||
| } | ||
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| private Decision underCapacity(ShardRouting shardRouting, RoutingNode node, RoutingAllocation allocation, | ||
| BiPredicate<Integer, Integer> decider) { | ||
| if (provisionedCapacity <= 0 || skewFactor < 0 ) { | ||
| return allocation.decision(Decision.YES, NAME, | ||
| "overload awareness allocation is not enabled, set cluster setting [%s] and cluster setting [%s] to enable it", | ||
| CLUSTER_ROUTING_ALLOCATION_LOAD_AWARENESS_SKEW_FACTOR_SETTING.getKey(), | ||
| CLUSTER_ROUTING_ALLOCATION_LOAD_AWARENESS_PROVISIONED_CAPACITY_SETTING.getKey()); | ||
| } | ||
| if (shardRouting.unassigned() && shardRouting.primary() && allowUnassignedPrimaries) { | ||
| return allocation.decision(Decision.YES, NAME, | ||
| "overload allocation awareness is allowed for unassigned primaries, set cluster setting [%s] to disable it", | ||
| CLUSTER_ROUTING_ALLOCATION_LOAD_AWARENESS_ALLOW_UNASSIGNED_PRIMARIES_SETTING.getKey()); | ||
| } | ||
| Metadata metadata = allocation.metadata(); | ||
| float expectedAvgShardsPerNode = (float) metadata.getTotalNumberOfShards() / provisionedCapacity; | ||
| int nodeShardCount = node.numberOfOwningShards(); | ||
| int limit = (int) Math.ceil(expectedAvgShardsPerNode * (1 + skewFactor / 100.0)); | ||
| if (decider.test(nodeShardCount, limit)) { | ||
| logger.debug(() -> new ParameterizedMessage("Too many shards [{}] allocated to this node [{}]. Expected average shards" + | ||
| " per node [{}], overload factor [{}], node limit [{}]", nodeShardCount, node.nodeId(), expectedAvgShardsPerNode, | ||
| skewFactor, limit)); | ||
| return allocation.decision(Decision.NO, NAME, "too many shards [%d] allocated to this node, limit per node [%d] considering" + | ||
| " overload factor [%.2f] based on capacity [%d]", nodeShardCount, limit, skewFactor, provisionedCapacity); | ||
| } | ||
| return allocation.decision(Decision.YES, NAME, "node meets all skew awareness attribute requirements"); | ||
| } | ||
| } |
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