[1.x] An allocation constraint mechanism, that de-prioritizes nodes from getting picked for allocation if they breach certain constraints (#777)

* An allocation constraint mechanism, that de-prioritizes nodes from getting picked for allocation if they breach certain constraints

Signed-off-by: Ashwin Pankaj <appankaj@amazon.com>

* Precommit fixes

Signed-off-by: Ashwin Pankaj <appankaj@amazon.com>

* Fix license header in test file

Signed-off-by: Ashwin Pankaj <appankaj@amazon.com>

* Review comments

Signed-off-by: Ashwin Pankaj <appankaj@amazon.com>

Co-authored-by: Pankaj <appankaj@88665a1e205d.ant.amazon.com>
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7 changed files with 862 additions and 13 deletions

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@ -0,0 +1,86 @@
/*
* Copyright OpenSearch Contributors.
* SPDX-License-Identifier: Apache-2.0
*/
package org.opensearch.cluster.routing.allocation;
import org.opensearch.cluster.routing.allocation.allocator.BalancedShardsAllocator;
import java.util.ArrayList;
import java.util.List;
import java.util.function.Predicate;
/**
* Allocation constraints specify conditions which, if breached, reduce the
* priority of a node for receiving shard allocations.
*/
public class AllocationConstraints {
public final long CONSTRAINT_WEIGHT = 1000000L;
private List<Predicate<ConstraintParams>> constraintPredicates;
public AllocationConstraints() {
this.constraintPredicates = new ArrayList<>(1);
this.constraintPredicates.add(isIndexShardsPerNodeBreached());
}
class ConstraintParams {
private BalancedShardsAllocator.Balancer balancer;
private BalancedShardsAllocator.ModelNode node;
private String index;
ConstraintParams(BalancedShardsAllocator.Balancer balancer, BalancedShardsAllocator.ModelNode node,
String index) {
this.balancer = balancer;
this.node = node;
this.index = index;
}
}
/**
* Evaluates configured allocation constraint predicates for given node - index
* combination; and returns a weight value based on the number of breached
* constraints.
*
* Constraint weight should be added to the weight calculated via weight
* function, to reduce priority of allocating on nodes with breached
* constraints.
*
* This weight function is used only in case of unassigned shards to avoid overloading a newly added node.
* Weight calculation in other scenarios like shard movement and re-balancing remain unaffected by this function.
*/
public long weight(BalancedShardsAllocator.Balancer balancer, BalancedShardsAllocator.ModelNode node,
String index) {
int constraintsBreached = 0;
ConstraintParams params = new ConstraintParams(balancer, node, index);
for (Predicate<ConstraintParams> predicate : constraintPredicates) {
if (predicate.test(params)) {
constraintsBreached++;
}
}
return constraintsBreached * CONSTRAINT_WEIGHT;
}
/**
* Constraint to control number of shards of an index allocated on a single
* node.
*
* In current weight function implementation, when a node has significantly
* fewer shards than other nodes (e.g. during single new node addition or node
* replacement), its weight is much less than other nodes. All shard allocations
* at this time tend to land on the new node with skewed weight. This breaks
* index level balance in the cluster, by creating all shards of the same index
* on one node, often resulting in a hotspot on that node.
*
* This constraint is breached when balancer attempts to allocate more than
* average shards per index per node.
*/
private Predicate<ConstraintParams> isIndexShardsPerNodeBreached() {
return (params) -> {
int currIndexShardsOnNode = params.node.numShards(params.index);
int allowedIndexShardsPerNode = (int) Math.ceil(params.balancer.avgShardsPerNode(params.index));
return (currIndexShardsOnNode >= allowedIndexShardsPerNode);
};
}
}

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@ -45,6 +45,7 @@ import org.opensearch.cluster.routing.ShardRoutingState;
import org.opensearch.cluster.routing.UnassignedInfo;
import org.opensearch.cluster.routing.UnassignedInfo.AllocationStatus;
import org.opensearch.cluster.routing.allocation.AllocateUnassignedDecision;
import org.opensearch.cluster.routing.allocation.AllocationConstraints;
import org.opensearch.cluster.routing.allocation.AllocationDecision;
import org.opensearch.cluster.routing.allocation.MoveDecision;
import org.opensearch.cluster.routing.allocation.NodeAllocationResult;
@ -192,7 +193,6 @@ public class BalancedShardsAllocator implements ShardsAllocator {
return weightFunction.shardBalance;
}
/**
* This class is the primary weight function used to create balanced over nodes and shards in the cluster.
* Currently this function has 3 properties:
@ -216,13 +216,16 @@ public class BalancedShardsAllocator implements ShardsAllocator {
* </li>
* </ul>
* <code>weight(node, index) = weight<sub>index</sub>(node, index) + weight<sub>node</sub>(node, index)</code>
*
* package-private for testing
*/
private static class WeightFunction {
static class WeightFunction {
private final float indexBalance;
private final float shardBalance;
private final float theta0;
private final float theta1;
private AllocationConstraints constraints;
WeightFunction(float indexBalance, float shardBalance) {
float sum = indexBalance + shardBalance;
@ -233,6 +236,12 @@ public class BalancedShardsAllocator implements ShardsAllocator {
theta1 = indexBalance / sum;
this.indexBalance = indexBalance;
this.shardBalance = shardBalance;
this.constraints = new AllocationConstraints();
}
public float weightWithAllocationConstraints(Balancer balancer, ModelNode node, String index) {
float balancerWeight = weight(balancer, node, index);
return balancerWeight + constraints.weight(balancer, node, index);
}
float weight(Balancer balancer, ModelNode node, String index) {
@ -411,7 +420,10 @@ public class BalancedShardsAllocator implements ShardsAllocator {
boolean deltaAboveThreshold = lessThan(currentDelta, threshold) == false;
// calculate the delta of the weights of the two nodes if we were to add the shard to the
// node in question and move it away from the node that currently holds it.
boolean betterWeightWithShardAdded = nodeWeight + 1.0f < currentWeight;
// hence we add 2.0f to the weight delta
float proposedDelta = 2.0f + nodeWeight - currentWeight;
boolean betterWeightWithShardAdded = proposedDelta < currentDelta;
rebalanceConditionsMet = deltaAboveThreshold && betterWeightWithShardAdded;
// if the simulated weight delta with the shard moved away is better than the weight delta
// with the shard remaining on the current node, and we are allowed to allocate to the
@ -964,7 +976,7 @@ public class BalancedShardsAllocator implements ShardsAllocator {
}
// weight of this index currently on the node
float currentWeight = weight.weight(this, node, shard.getIndexName());
float currentWeight = weight.weightWithAllocationConstraints(this, node, shard.getIndexName());
// moving the shard would not improve the balance, and we are not in explain mode, so short circuit
if (currentWeight > minWeight && explain == false) {
continue;
@ -1002,7 +1014,7 @@ public class BalancedShardsAllocator implements ShardsAllocator {
updateMinNode = currentDecision.type() == Type.YES;
}
} else {
updateMinNode = true;
updateMinNode = currentWeight < minWeight;
}
if (updateMinNode) {
minNode = node;
@ -1086,7 +1098,7 @@ public class BalancedShardsAllocator implements ShardsAllocator {
}
static class ModelNode implements Iterable<ModelIndex> {
public static class ModelNode implements Iterable<ModelIndex> {
private final Map<String, ModelIndex> indices = new HashMap<>();
private int numShards = 0;
private final RoutingNode routingNode;

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@ -0,0 +1,65 @@
/*
* 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.
*/
package org.opensearch.cluster.routing.allocation;
import org.opensearch.cluster.OpenSearchAllocationTestCase;
import org.opensearch.cluster.routing.allocation.allocator.BalancedShardsAllocator;
import org.opensearch.common.settings.ClusterSettings;
import org.opensearch.common.settings.Settings;
import static org.mockito.Matchers.anyString;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.when;
public class AllocationConstraintsTests extends OpenSearchAllocationTestCase {
public void testSettings() {
Settings.Builder settings = Settings.builder();
ClusterSettings service = new ClusterSettings(Settings.builder().build(),
ClusterSettings.BUILT_IN_CLUSTER_SETTINGS);
BalancedShardsAllocator allocator = new BalancedShardsAllocator(settings.build(), service);
settings = Settings.builder();
float indexBalanceFactor = randomFloat();
float shardBalance = randomFloat();
float threshold = randomFloat();
settings.put(BalancedShardsAllocator.INDEX_BALANCE_FACTOR_SETTING.getKey(), indexBalanceFactor);
settings.put(BalancedShardsAllocator.SHARD_BALANCE_FACTOR_SETTING.getKey(), shardBalance);
settings.put(BalancedShardsAllocator.THRESHOLD_SETTING.getKey(), threshold);
service.applySettings(settings.build());
assertEquals(indexBalanceFactor, allocator.getIndexBalance(), 0.01);
assertEquals(shardBalance, allocator.getShardBalance(), 0.01);
assertEquals(threshold, allocator.getThreshold(), 0.01);
}
/**
* Test constraint evaluation logic when with different values of ConstraintMode
* for IndexShardPerNode constraint satisfied and breached.
*/
public void testIndexShardsPerNodeConstraint() {
BalancedShardsAllocator.Balancer balancer = mock(BalancedShardsAllocator.Balancer.class);
BalancedShardsAllocator.ModelNode node = mock(BalancedShardsAllocator.ModelNode.class);
AllocationConstraints constraints = new AllocationConstraints();
int shardCount = randomIntBetween(1, 500);
float avgShardsPerNode = 1.0f + (random().nextFloat()) * 999.0f;
when(balancer.avgShardsPerNode(anyString())).thenReturn(avgShardsPerNode);
when(node.numShards(anyString())).thenReturn(shardCount);
when(node.getNodeId()).thenReturn("test-node");
long expectedWeight = (shardCount >= avgShardsPerNode) ? constraints.CONSTRAINT_WEIGHT : 0;
assertEquals(expectedWeight, constraints.weight(balancer, node, "index"));
}
}

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@ -0,0 +1,202 @@
/*
* 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.
*/
package org.opensearch.cluster.routing.allocation;
import org.opensearch.cluster.ClusterInfo;
import org.opensearch.cluster.ClusterInfoService;
import org.opensearch.cluster.ClusterState;
import org.opensearch.cluster.DiskUsage;
import org.opensearch.cluster.OpenSearchAllocationWithConstraintsTestCase;
import org.opensearch.cluster.node.DiscoveryNodes;
import org.opensearch.cluster.routing.ShardRouting;
import org.opensearch.common.collect.ImmutableOpenMap;
import org.opensearch.common.settings.Settings;
import org.opensearch.index.shard.ShardId;
import org.opensearch.test.VersionUtils;
import java.util.HashMap;
import java.util.Map;
import static org.opensearch.cluster.routing.ShardRoutingState.STARTED;
import static org.opensearch.cluster.routing.ShardRoutingState.UNASSIGNED;
public class IndexShardConstraintDeciderOverlapTests extends OpenSearchAllocationWithConstraintsTestCase {
/**
* High watermark breach blocks new shard allocations to affected nodes. If shard count on such
* nodes is low, this will cause IndexShardPerNodeConstraint to breach.
*
* This test verifies that this doesn't lead to unassigned shards, and there are no hot spots in eligible
* nodes.
*/
public void testHighWatermarkBreachWithLowShardCount() {
setupInitialCluster(3, 15, 10, 1);
addNodesWithIndexing(1, "high_watermark_node_", 6, 5, 1);
// Disk threshold settings enabled
Settings settings = Settings.builder()
.put(DiskThresholdSettings.CLUSTER_ROUTING_ALLOCATION_DISK_THRESHOLD_ENABLED_SETTING.getKey(), true)
.put(DiskThresholdSettings.CLUSTER_ROUTING_ALLOCATION_LOW_DISK_WATERMARK_SETTING.getKey(), 0.7)
.put(DiskThresholdSettings.CLUSTER_ROUTING_ALLOCATION_HIGH_DISK_WATERMARK_SETTING.getKey(), 0.8)
.put(DiskThresholdSettings.CLUSTER_ROUTING_ALLOCATION_DISK_FLOOD_STAGE_WATERMARK_SETTING.getKey(), 0.95)
.put("cluster.routing.allocation.node_concurrent_recoveries", 1)
.put("cluster.routing.allocation.cluster_concurrent_recoveries", 1)
.build();
// Build Shard size and disk usages
ImmutableOpenMap.Builder<String, DiskUsage> usagesBuilder = ImmutableOpenMap.builder();
usagesBuilder.put("node_0", new DiskUsage("node_0", "node_0", "/dev/null", 100, 80)); // 20% used
usagesBuilder.put("node_1", new DiskUsage("node_1", "node_1", "/dev/null", 100, 55)); // 45% used
usagesBuilder.put("node_2", new DiskUsage("node_2", "node_2", "/dev/null", 100, 35)); // 65% used
usagesBuilder.put("high_watermark_node_0",
new DiskUsage("high_watermark_node_0", "high_watermark_node_0", "/dev/null", 100, 10)); // 90% used
ImmutableOpenMap<String, DiskUsage> usages = usagesBuilder.build();
ImmutableOpenMap.Builder<String, Long> shardSizesBuilder = ImmutableOpenMap.builder();
clusterState.getRoutingTable().allShards().forEach(shard ->
shardSizesBuilder.put(shardIdentifierFromRouting(shard), 1L)); // Each shard is 1 byte
ImmutableOpenMap<String, Long> shardSizes = shardSizesBuilder.build();
final ImmutableOpenMap<ClusterInfo.NodeAndPath, ClusterInfo.ReservedSpace> reservedSpace =
new ImmutableOpenMap.Builder<ClusterInfo.NodeAndPath, ClusterInfo.ReservedSpace>()
.fPut(
getNodeAndDevNullPath("node_0"), getReservedSpace()
)
.fPut(
getNodeAndDevNullPath("node_1"), getReservedSpace()
)
.fPut(
getNodeAndDevNullPath("node_2"), getReservedSpace()
)
.fPut(
getNodeAndDevNullPath("high_watermark_node_0"), getReservedSpace()
)
.build();
final ClusterInfo clusterInfo = new DevNullClusterInfo(usages, usages, shardSizes, reservedSpace);
ClusterInfoService cis = () -> clusterInfo;
allocation = createAllocationService(settings, cis);
allocateAndCheckIndexShardHotSpots(false, 3, "node_0", "node_1", "node_2");
assertForIndexShardHotSpots(true, 4);
assertTrue(clusterState.getRoutingTable().shardsWithState(UNASSIGNED).isEmpty());
assertTrue(clusterState.getRoutingNodes().node("high_watermark_node_0").isEmpty());
/* Shard sizes that would breach high watermark on node_2 if allocated.
*/
addIndices("big_index_", 1, 10, 0);
ImmutableOpenMap.Builder<String, Long> bigIndexShardSizeBuilder = ImmutableOpenMap.builder(shardSizes);
clusterState.getRoutingNodes().unassigned()
.forEach(shard -> bigIndexShardSizeBuilder.put(shardIdentifierFromRouting(shard), 20L));
shardSizes = bigIndexShardSizeBuilder.build();
final ClusterInfo bigIndexClusterInfo = new DevNullClusterInfo(usages, usages, shardSizes, reservedSpace);
cis = () -> bigIndexClusterInfo;
allocation = createAllocationService(settings, cis);
allocateAndCheckIndexShardHotSpots(false, 2, "node_0", "node_1");
assertForIndexShardHotSpots(true, 4);
assertTrue(clusterState.getRoutingTable().shardsWithState(UNASSIGNED).isEmpty());
for (ShardRouting shard: clusterState.getRoutingTable().index("big_index_0").shardsWithState(STARTED)) {
assertNotEquals("node_2", shard.currentNodeId());
}
}
private ClusterInfo.NodeAndPath getNodeAndDevNullPath(String node) {
return new ClusterInfo.NodeAndPath(node, "/dev/null");
}
private ClusterInfo.ReservedSpace getReservedSpace() {
return new ClusterInfo.ReservedSpace.Builder().add(new ShardId("", "", 0), 2).build();
}
/**
* Test clusters with subset of nodes on older version.
* New version shards should not migrate to old version nodes, even if this creates potential hot spots.
*/
public void testNodeVersionCompatibilityOverlap() {
setupInitialCluster(3, 6, 10, 1);
// Add an old version node and exclude a new version node
DiscoveryNodes.Builder nb = DiscoveryNodes.builder(clusterState.nodes())
.add(newNode("old_node", VersionUtils.getPreviousVersion()));
clusterState = ClusterState.builder(clusterState).nodes(nb.build()).build();
buildAllocationService("node_0");
// Shards should only go to remaining new version nodes
allocateAndCheckIndexShardHotSpots(false, 2, "node_1", "node_2");
assertForIndexShardHotSpots(true, 4);
assertTrue(clusterState.getRoutingTable().shardsWithState(UNASSIGNED).isEmpty());
for (ShardRouting shard: clusterState.getRoutingTable().allShards()) {
assertNotEquals("node_0", shard.currentNodeId());
assertNotEquals("old_node", shard.currentNodeId());
}
}
/**
* Test zone aware clusters with balanced zones.
* No hot spots expected.
*/
public void testZoneBalanced() {
Map<String, Integer> nodesPerZone = new HashMap<>();
nodesPerZone.put("zone_0", 3);
nodesPerZone.put("zone_1", 3);
createEmptyZoneAwareCluster(nodesPerZone);
addIndices("index_", 4, 5, 1);
buildZoneAwareAllocationService();
allocateAndCheckIndexShardHotSpots(false, 6);
resetCluster();
buildZoneAwareAllocationService();
allocateAndCheckIndexShardHotSpots(false, 6);
}
/**
* Test zone aware clusters with unbalanced zones.
* Hot spots expected as awareness forces shards per zone restrictions.
*/
public void testZoneUnbalanced() {
Map<String, Integer> nodesPerZone = new HashMap<>();
nodesPerZone.put("zone_0", 5);
nodesPerZone.put("zone_1", 1);
createEmptyZoneAwareCluster(nodesPerZone);
addIndices("index_", 1, 5, 1);
updateInitialCluster();
buildZoneAwareAllocationService();
clusterState = allocateShardsAndBalance(clusterState);
assertForIndexShardHotSpots(true, 6);
assertTrue(clusterState.getRoutingTable().shardsWithState(UNASSIGNED).isEmpty());
resetCluster();
buildZoneAwareAllocationService();
clusterState = allocateShardsAndBalance(clusterState);
assertForIndexShardHotSpots(true, 6);
assertTrue(clusterState.getRoutingTable().shardsWithState(UNASSIGNED).isEmpty());
}
/**
* ClusterInfo that always points to DevNull.
*/
public static class DevNullClusterInfo extends ClusterInfo {
public DevNullClusterInfo(ImmutableOpenMap<String, DiskUsage> leastAvailableSpaceUsage,
ImmutableOpenMap<String, DiskUsage> mostAvailableSpaceUsage,
ImmutableOpenMap<String, Long> shardSizes,
ImmutableOpenMap<NodeAndPath, ReservedSpace> reservedSpace) {
super(leastAvailableSpaceUsage, mostAvailableSpaceUsage, shardSizes, null, reservedSpace);
}
@Override
public String getDataPath(ShardRouting shardRouting) {
return "/dev/null";
}
}
}

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@ -0,0 +1,123 @@
/*
* 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.
*/
package org.opensearch.cluster.routing.allocation;
import org.opensearch.cluster.OpenSearchAllocationWithConstraintsTestCase;
public class IndexShardHotSpotTests extends OpenSearchAllocationWithConstraintsTestCase {
/**
* Test single node replacement without active indexing.
*/
public void testNodeReplacement() {
setupInitialCluster(5, 1, 5, 1);
terminateNodes("node_1");
assertForIndexShardHotSpots(false, 4);
addNodesWithoutIndexing(1, "new_node_");
int movesForModeNone = allocateAndCheckIndexShardHotSpots(false, 5, "new_node_0");
setupInitialCluster(5, 1, 5, 1);
terminateNodes("node_1");
assertForIndexShardHotSpots(false, 4);
addNodesWithoutIndexing(1, "new_node_");
int movesForModeUnassigned = allocateAndCheckIndexShardHotSpots(false, 5, "new_node_0");
assertTrue(movesForModeUnassigned <= movesForModeNone);
}
/**
* Test single node replacement with active indexing.
*/
public void testNodeReplacementWithIndexing() {
setupInitialCluster(5, 30, 5, 1);
buildAllocationService();
terminateNodes("node_1");
assertForIndexShardHotSpots(false, 4);
addNodesWithIndexing(1, "new_node_", 3, 20, 1);
int movesForModeNone = allocateAndCheckIndexShardHotSpots(false, 5, "new_node_0");
resetCluster();
buildAllocationService();
terminateNodes("node_1");
assertForIndexShardHotSpots(false, 4);
addNodesWithIndexing(1, "new_node_", 3, 20, 1);
int movesForModeUnassigned = allocateAndCheckIndexShardHotSpots(false, 5, "new_node_0");
assertTrue(movesForModeUnassigned <= movesForModeNone);
}
/**
* Test skewed cluster scale out via single node addition during active indexing.
*/
public void testSkewedClusterScaleOut() {
setupInitialCluster(3, 30, 10, 1);
buildAllocationService();
addNodesWithIndexing(1, "new_node_", 8, 10, 1);
int movesForModeNone = allocateAndCheckIndexShardHotSpots( false, 4, "new_node_0");
resetCluster();
buildAllocationService();
addNodesWithIndexing(1, "new_node_", 8, 10, 1);
int movesForModeUnassigned = allocateAndCheckIndexShardHotSpots(false, 4, "new_node_0");
assertTrue(movesForModeUnassigned <= movesForModeNone);
}
/**
* Test under replicated yellow cluster scale out to green.
*
* This scenario is not expected to create hotspots even without constraints enabled. The
* test is a sanity check to ensure allocation constraints don't worsen the situation.
*/
public void testUnderReplicatedClusterScaleOut() {
setupInitialCluster(3, 30, 10, 3);
buildAllocationService();
addNodesWithoutIndexing(1, "new_node_");
int movesForModeNone = allocateAndCheckIndexShardHotSpots(false, 4, "new_node_0");
resetCluster();
buildAllocationService();
addNodesWithoutIndexing(1, "new_node_");
int movesForModeUnassigned = allocateAndCheckIndexShardHotSpots(false, 4, "new_node_0");
assertTrue(movesForModeUnassigned <= movesForModeNone);
}
/**
* Test cluster scale in scenario, when nodes are gracefully excluded from
* cluster before termination.
*
* During moveShards(), shards are picked from across indexes in an interleaved manner.
* This prevents hot spots by evenly picking up shards. Since shard order can change
* in subsequent runs, we are not guaranteed to less moves than no allocation constraint run.
*
* Move tests are hence just a sanity test, to ensure we don't create any unexpected hot spots with
* allocation settings.
*/
public void testClusterScaleIn() {
setupInitialCluster(4, 30, 10, 1);
buildAllocationService("node_0,node_1");
allocateAndCheckIndexShardHotSpots(false, 2, "node_2", "node_3");
resetCluster();
buildAllocationService("node_0,node_1");
allocateAndCheckIndexShardHotSpots(false, 2, "node_2", "node_3");
}
/**
* Test cluster scale in scenario with skewed shard distribution in remaining nodes.
*/
public void testClusterScaleInWithSkew() {
setupInitialCluster(4, 100, 5, 1);
buildAllocationService("node_0,node_1");
addNodesWithoutIndexing(1, "new_node_");
allocateAndCheckIndexShardHotSpots(false, 3, "node_2", "node_3", "new_node_0");
resetCluster();
buildAllocationService("node_0,node_1");
addNodesWithoutIndexing(1, "new_node_");
allocateAndCheckIndexShardHotSpots(false, 3, "node_2", "node_3", "new_node_0");
}
}

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@ -34,6 +34,7 @@ package org.opensearch.cluster.routing.allocation;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.hamcrest.Matcher;
import org.opensearch.Version;
import org.opensearch.cluster.ClusterState;
import org.opensearch.cluster.OpenSearchAllocationTestCase;
@ -48,7 +49,13 @@ import org.opensearch.common.settings.Settings;
import static org.opensearch.cluster.routing.ShardRoutingState.RELOCATING;
import static org.opensearch.cluster.routing.ShardRoutingState.STARTED;
import java.util.Set;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import static org.hamcrest.Matchers.equalTo;
import static org.hamcrest.Matchers.anyOf;
public class ShardsLimitAllocationTests extends OpenSearchAllocationTestCase {
private final Logger logger = LogManager.getLogger(ShardsLimitAllocationTests.class);
@ -201,13 +208,20 @@ public class ShardsLimitAllocationTests extends OpenSearchAllocationTestCase {
clusterState = startInitializingShardsAndReroute(strategy, clusterState);
assertThat(RoutingNodesUtils.numberOfShardsOfType(clusterState.getRoutingNodes(), STARTED), equalTo(10));
// AllocationConstraints will choose node2 for 3 test1 shards and the rest are assigned to node1
// These shards then relocate to node2 after balanceByWeights() is invoked
assertThat(RoutingNodesUtils.numberOfShardsOfType(clusterState.getRoutingNodes(), STARTED), equalTo(8));
assertThat(RoutingNodesUtils.numberOfShardsOfType(clusterState.getRoutingNodes(), RELOCATING), equalTo(2));
// Expected values depend on which index shards were chosen for relocation.
String relocatingIndex = getRelocatingIndex(clusterState);
Matcher<String> node1Matcher = anyOf(equalTo("test"), equalTo("test1"));
Matcher<String> node2Matcher = relocatingIndex.equals("test1") ? equalTo("test1") : node1Matcher;
for (ShardRouting shardRouting : clusterState.getRoutingNodes().node("node1")) {
assertThat(shardRouting.getIndexName(), equalTo("test"));
assertThat(shardRouting.getIndexName(), node1Matcher);
}
for (ShardRouting shardRouting : clusterState.getRoutingNodes().node("node2")) {
assertThat(shardRouting.getIndexName(), equalTo("test1"));
assertThat(shardRouting.getIndexName(), node2Matcher);
}
logger.info("update {} for test, see that things move",
@ -226,10 +240,12 @@ public class ShardsLimitAllocationTests extends OpenSearchAllocationTestCase {
logger.info("reroute after setting");
clusterState = strategy.reroute(clusterState, "reroute");
assertThat(clusterState.getRoutingNodes().node("node1").numberOfShardsWithState(STARTED), equalTo(3));
assertThat(clusterState.getRoutingNodes().node("node1").numberOfShardsWithState(RELOCATING), equalTo(2));
assertThat(clusterState.getRoutingNodes().node("node2").numberOfShardsWithState(RELOCATING), equalTo(2));
assertThat(clusterState.getRoutingNodes().node("node2").numberOfShardsWithState(STARTED), equalTo(3));
int node1RelocCount = relocatingIndex.equals("test1") ? 4 : 2;
assertThat(clusterState.getRoutingNodes().node("node1").numberOfShardsWithState(RELOCATING), equalTo(node1RelocCount));
int node2RelocCount = relocatingIndex.equals("test1") ? 2 : 0;
assertThat(clusterState.getRoutingNodes().node("node2").numberOfShardsWithState(RELOCATING), equalTo(node2RelocCount));
assertThat(clusterState.getRoutingNodes().node("node2").numberOfShardsWithState(STARTED), equalTo(3 - node2RelocCount));
// the first move will destroy the balance and the balancer will move 2 shards from node2 to node one right after
// moving the nodes to node2 since we consider INITIALIZING nodes during rebalance
clusterState = startInitializingShardsAndReroute(strategy, clusterState);
@ -237,4 +253,13 @@ public class ShardsLimitAllocationTests extends OpenSearchAllocationTestCase {
assertThat(clusterState.getRoutingNodes().node("node1").numberOfShardsWithState(STARTED), equalTo(5));
assertThat(clusterState.getRoutingNodes().node("node2").numberOfShardsWithState(STARTED), equalTo(5));
}
private String getRelocatingIndex(ClusterState clusterState) {
final Set<String> indices = Stream.of(clusterState.getRoutingNodes())
.flatMap(node -> node.shardsWithState(RELOCATING).stream().map(x -> x.getIndexName()))
.collect(Collectors.toSet());
assertThat(indices.size(), equalTo(1));
return indices.iterator().next();
}
}

View File

@ -0,0 +1,336 @@
/*
* Copyright OpenSearch Contributors.
* SPDX-License-Identifier: Apache-2.0
*/
package org.opensearch.cluster;
import org.opensearch.Version;
import org.opensearch.cluster.metadata.IndexMetadata;
import org.opensearch.cluster.metadata.Metadata;
import org.opensearch.cluster.node.DiscoveryNodes;
import org.opensearch.cluster.routing.RoutingNode;
import org.opensearch.cluster.routing.RoutingTable;
import org.opensearch.cluster.routing.ShardRouting;
import org.opensearch.cluster.routing.UnassignedInfo;
import org.opensearch.common.settings.Settings;
import org.opensearch.common.util.CollectionUtils;
import org.junit.Before;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import static java.util.Collections.singletonMap;
import static org.opensearch.cluster.routing.ShardRoutingState.INITIALIZING;
import static org.opensearch.cluster.routing.ShardRoutingState.STARTED;
public abstract class OpenSearchAllocationWithConstraintsTestCase extends OpenSearchAllocationTestCase {
protected MockAllocationService allocation;
private ClusterState initialClusterState;
protected ClusterState clusterState;
private HashMap<String, Integer> indexShardCount;
private HashMap<String, HashMap<String, Integer>> nodeShardsByIndex;
private static final int MAX_REROUTE_STEPS_ALLOWED = 1500;
@Before
public void clearState() {
allocation = null;
initialClusterState = null;
clusterState = null;
indexShardCount = null;
nodeShardsByIndex = null;
}
public static String shardIdentifierFromRouting(ShardRouting shardRouting) {
return shardRouting.shardId().toString() + "[" + (shardRouting.primary() ? "p" : "r") + "]";
}
public void buildAllocationService() {
Settings.Builder sb = Settings.builder();
buildAllocationService(sb);
}
public void buildAllocationService(String excludeNodes) {
logger.info("Excluding nodes: [{}]", excludeNodes);
Settings.Builder sb = Settings.builder().put("cluster.routing.allocation.exclude._node_id", excludeNodes);
buildAllocationService(sb);
}
public void buildZoneAwareAllocationService() {
logger.info("Creating zone aware cluster");
Settings.Builder sb = Settings.builder().put("cluster.routing.allocation.awareness.attributes", "zone");
buildAllocationService(sb);
}
public void buildAllocationService(Settings.Builder sb) {
sb.put("cluster.routing.allocation.node_concurrent_recoveries", 1);
sb.put("cluster.routing.allocation.cluster_concurrent_rebalance", 1);
allocation = createAllocationService(sb.build());
}
public Metadata buildMetadata(Metadata.Builder mb, String indexPrefix, int numberOfIndices, int numberOfShards,
int numberOfReplicas) {
for (int i = 0; i < numberOfIndices; i++) {
mb.put(IndexMetadata.builder(indexPrefix + i)
.settings(settings(Version.CURRENT)
.put(UnassignedInfo.INDEX_DELAYED_NODE_LEFT_TIMEOUT_SETTING.getKey(), "0"))
.numberOfShards(numberOfShards).numberOfReplicas(numberOfReplicas));
}
return mb.build();
}
public RoutingTable buildRoutingTable(RoutingTable.Builder rb, Metadata metadata, String indexPrefix,
int numberOfIndices) {
for (int i = 0; i < numberOfIndices; i++) {
rb.addAsNew(metadata.index(indexPrefix + i));
}
return rb.build();
}
public DiscoveryNodes addNodes(DiscoveryNodes.Builder nb, String nodePrefix, int nodesAdded) {
for (int i = 0; i < nodesAdded; i++) {
nb.add(newNode(nodePrefix + i, singletonMap("_node_id", nodePrefix + i)));
}
return nb.build();
}
public void resetCluster() {
clusterState = initialClusterState;
}
public void updateInitialCluster() {
initialClusterState = clusterState;
}
public void createEmptyZoneAwareCluster(Map<String, Integer> nodesPerZone) {
DiscoveryNodes.Builder nb = DiscoveryNodes.builder();
int nodeId = 0;
for (String zone : nodesPerZone.keySet()) {
for (int i = 0; i < nodesPerZone.get(zone); i++) {
nb.add(newNode("node_" + nodeId, singletonMap("zone", zone)));
nodeId++;
}
}
initialClusterState = ClusterState.builder(ClusterName.DEFAULT).nodes(nb.build()).build();
clusterState = initialClusterState;
}
public void setupInitialCluster(int nodeCount, int indices, int shards, int replicas) {
final String DEFAULT_INDEX_PREFIX = "index_";
final String DEFAULT_NODE_PREFIX = "node_";
Metadata metadata = buildMetadata(Metadata.builder(), DEFAULT_INDEX_PREFIX, indices, shards, replicas);
RoutingTable routingTable = buildRoutingTable(RoutingTable.builder(), metadata, DEFAULT_INDEX_PREFIX, indices);
DiscoveryNodes nodes = addNodes(DiscoveryNodes.builder(), DEFAULT_NODE_PREFIX, nodeCount);
initialClusterState = ClusterState.builder(ClusterName.DEFAULT).metadata(metadata).routingTable(routingTable)
.nodes(nodes).build();
buildAllocationService();
initialClusterState = allocateShardsAndBalance(initialClusterState);
clusterState = initialClusterState;
indexShardCount = new HashMap<>();
for (int i = 0; i < indices; i++) {
indexShardCount.put(DEFAULT_INDEX_PREFIX + i, shards * (replicas + 1));
}
assertForIndexShardHotSpots(false, nodeCount); // Initial cluster should be balanced
logger.info("Initial cluster created...");
}
public void buildNodeShardsByIndex() {
nodeShardsByIndex = new HashMap<>();
for (RoutingNode rn : clusterState.getRoutingNodes()) {
String node = rn.nodeId();
nodeShardsByIndex.put(node, new HashMap<>());
for (ShardRouting shard : rn) {
assert shard.currentNodeId().equals(node);
if (shard.state() == INITIALIZING || shard.state() == STARTED) {
nodeShardsByIndex.get(node).merge(shard.getIndexName(), 1, Integer::sum);
}
}
}
}
public boolean isIndexHotSpotPresent(int nodes, List<String> nodeList) {
for (String node : nodeList) {
for (String index : nodeShardsByIndex.get(node).keySet()) {
int count = nodeShardsByIndex.get(node).get(index);
int limit = (int) Math.ceil(indexShardCount.get(index) / (float) nodes);
if (count > limit) {
return true;
}
}
}
return false;
}
public List<String> getNodeList(String... nodesToValidate) {
if (CollectionUtils.isEmpty(nodesToValidate)) {
return Arrays.asList(clusterState.getNodes().resolveNodes());
}
return Arrays.asList(nodesToValidate);
}
public void assertForIndexShardHotSpots(boolean expected, int nodes, String... nodesToValidate) {
List<String> nodeList = getNodeList(nodesToValidate);
buildNodeShardsByIndex();
assertEquals(expected, isIndexHotSpotPresent(nodes, nodeList));
}
public int allocateAndCheckIndexShardHotSpots(boolean expected, int nodes, String... nodesToValidate) {
List<String> nodeList = getNodeList(nodesToValidate);
boolean hasHotSpot = false;
buildNodeShardsByIndex();
List<ShardRouting> initShards;
int movesToBalance = 0;
do {
assert movesToBalance <= MAX_REROUTE_STEPS_ALLOWED : "Could not balance cluster in max allowed moves";
clusterState = allocation.applyStartedShards(clusterState,
clusterState.getRoutingNodes().shardsWithState(INITIALIZING));
clusterState = allocation.reroute(clusterState, "reroute");
initShards = clusterState.getRoutingNodes().shardsWithState(INITIALIZING);
for (ShardRouting shard : initShards) {
String node = shard.currentNodeId();
String index = shard.getIndexName();
nodeShardsByIndex.get(node).merge(index, 1, Integer::sum);
if (!nodeList.contains(node)) {
continue;
}
int count = nodeShardsByIndex.get(node).get(index);
int limit = (int) Math.ceil(indexShardCount.get(index) / (float) nodes);
if (count <= limit) {
continue;
}
/**
* Hot spots can occur due to the order in which shards get allocated to nodes.
* A node with fewer shards may not be able to accept current shard due to
* SameShardAllocationDecider, causing it to breach allocation constraint on
* another node. We need to differentiate between such hot spots v/s actual hot
* spots.
*
* A simple check could be to ensure there is no node with shards less than
* allocation limit, that can accept current shard. However, in current
* allocation algorithm, when nodes get throttled, shards are added to
* ModelNodes without adding them to actual cluster (RoutingNodes). As a result,
* the shards per node we see here, are different from the ones observed by
* weight function in balancer. RoutingNodes with {@link count} < {@link limit}
* may not have had the same count in the corresponding ModelNode seen by weight
* function. We hence use the following alternate check --
*
* Given the way {@link limit} is defined, we should not have hot spots if *all*
* nodes are eligible to accept the shard. A hot spot is acceptable, if either
* all peer nodes have {@link count} > {@link limit}, or if even one node is
* ineligible to accept the shard due to SameShardAllocationDecider, as this
* leads to a chain of events that breach IndexShardsPerNode constraint on all
* other nodes.
*/
// If all peer nodes have count >= limit, hotspot is acceptable
boolean limitBreachedOnAllNodes = true;
for (RoutingNode peerNode : clusterState.getRoutingNodes()) {
if (peerNode.nodeId().equals(node)) {
continue;
}
int peerCount = nodeShardsByIndex.get(peerNode.nodeId()).getOrDefault(index, 0);
if (peerCount < limit) {
limitBreachedOnAllNodes = false;
}
}
if (limitBreachedOnAllNodes) {
continue;
}
// If any node is ineligible to accept the shard, this hot spot is acceptable
boolean peerHasSameShard = false;
for (RoutingNode peerNode : clusterState.getRoutingNodes()) {
if (peerNode.nodeId().equals(node)) {
continue;
}
ShardRouting sameIdShardOnPeer = peerNode.getByShardId(shard.shardId());
if (sameIdShardOnPeer != null && sameIdShardOnPeer.getIndexName().equals(index)) {
peerHasSameShard = true;
}
}
if (peerHasSameShard) {
continue;
}
hasHotSpot = true;
}
movesToBalance++;
} while (!initShards.isEmpty());
logger.info("HotSpot: [{}], Moves to balance: [{}]", hasHotSpot, movesToBalance);
assertEquals(expected, hasHotSpot);
assertForIndexShardHotSpots(false, nodes); // Post re-balancing, cluster should always be hot spot free.
return movesToBalance;
}
public ClusterState allocateShardsAndBalance(ClusterState clusterState) {
int iterations = 0;
do {
clusterState = allocation.applyStartedShards(clusterState,
clusterState.getRoutingNodes().shardsWithState(INITIALIZING));
clusterState = allocation.reroute(clusterState, "reroute");
iterations++;
} while (!clusterState.getRoutingNodes().shardsWithState(INITIALIZING).isEmpty()
&& iterations < MAX_REROUTE_STEPS_ALLOWED);
return clusterState;
}
public void addNodesWithoutIndexing(int nodeCount, String node_prefix) {
DiscoveryNodes nodes = addNodes(DiscoveryNodes.builder(clusterState.nodes()), node_prefix, nodeCount);
clusterState = ClusterState.builder(clusterState).nodes(nodes).build();
}
public void terminateNodes(String... nodesToTerminate) {
if (CollectionUtils.isEmpty(nodesToTerminate)) {
return;
}
DiscoveryNodes.Builder nb = DiscoveryNodes.builder(clusterState.nodes());
Arrays.asList(nodesToTerminate).forEach(node -> nb.remove(node));
clusterState = ClusterState.builder(clusterState).nodes(nb.build()).build();
clusterState = allocation.disassociateDeadNodes(clusterState, true, "node-terminated");
clusterState = allocateShardsAndBalance(clusterState);
}
public void addNodesWithIndexing(int nodeCount, String node_prefix, int indices, int shards, int replicas) {
final String NEW_INDEX_PREFIX = "new_index_";
Metadata md = buildMetadata(Metadata.builder(clusterState.getMetadata()), NEW_INDEX_PREFIX, indices, shards,
replicas);
RoutingTable rb = buildRoutingTable(RoutingTable.builder(clusterState.getRoutingTable()), md, NEW_INDEX_PREFIX,
indices);
DiscoveryNodes nodes = addNodes(DiscoveryNodes.builder(clusterState.nodes()), node_prefix, nodeCount);
clusterState = ClusterState.builder(clusterState).metadata(md).routingTable(rb).nodes(nodes).build();
for (int i = 0; i < indices; i++) {
indexShardCount.put(NEW_INDEX_PREFIX + i, shards * (replicas + 1));
}
}
public void addIndices(String index_prefix, int indices, int shards, int replicas) {
Metadata md = buildMetadata(Metadata.builder(clusterState.getMetadata()), index_prefix, indices, shards,
replicas);
RoutingTable rb = buildRoutingTable(RoutingTable.builder(clusterState.getRoutingTable()), md, index_prefix,
indices);
clusterState = ClusterState.builder(clusterState).metadata(md).routingTable(rb).build();
if (indexShardCount == null) {
indexShardCount = new HashMap<>();
}
for (int i = 0; i < indices; i++) {
indexShardCount.put(index_prefix + i, shards * (replicas + 1));
}
}
}