Module org.elasticsearch.server

Package org.elasticsearch.cluster.routing.allocation.allocator

Class BalancedShardsAllocator

java.lang.Object

org.elasticsearch.cluster.routing.allocation.allocator.BalancedShardsAllocator

All Implemented Interfaces:

ShardsAllocator

public class BalancedShardsAllocator
extends Object
implements ShardsAllocator

The BalancedShardsAllocator allocates and balances shards on the cluster nodes using WeightFunction. The balancing attempts to:

• even shard count across nodes (weighted by cluster.routing.allocation.balance.shard)
• spread shards of the same index across different nodes (weighted by cluster.routing.allocation.balance.index)
• even write load of the data streams write indices across nodes (weighted by cluster.routing.allocation.balance.write_load)
• even disk usage across nodes (weighted by cluster.routing.allocation.balance.disk_usage)

The sensitivity of the algorithm is defined by cluster.routing.allocation.balance.threshold. Allocator takes into account constraints set by AllocationDeciders when allocating and balancing shards.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	BalancedShardsAllocator.Balancer	A BalancedShardsAllocator.Balancer
static class	BalancedShardsAllocator.ModelNode
static final class	BalancedShardsAllocator.NodeSorter	A NodeSorter sorts the set of nodes for a single partition using the WeightFunction for that partition.
static final record	BalancedShardsAllocator.ProjectIndex

Field Summary

Fields

Modifier and Type	Field	Description
static final Setting<Float>	DISK_USAGE_BALANCE_FACTOR_SETTING
static final Setting<Float>	INDEX_BALANCE_FACTOR_SETTING
static final Setting<TimeValue>	INVALID_WEIGHTS_MINIMUM_LOG_INTERVAL
static final Setting<Float>	SHARD_BALANCE_FACTOR_SETTING
static final Setting<Float>	THRESHOLD_SETTING
static final Setting<Float>	WRITE_LOAD_BALANCE_FACTOR_SETTING

Constructor Summary

Constructors

Constructor	Description
BalancedShardsAllocator()
BalancedShardsAllocator(BalancerSettings balancerSettings, WriteLoadForecaster writeLoadForecaster)
BalancedShardsAllocator(BalancerSettings balancerSettings, WriteLoadForecaster writeLoadForecaster, BalancingWeightsFactory balancingWeightsFactory)
BalancedShardsAllocator(Settings settings)

Method Summary

Modifier and Type	Method	Description
void	allocate(RoutingAllocation allocation)	Allocates shards to nodes in the cluster.
ShardAllocationDecision	explainShardAllocation(ShardRouting shard, RoutingAllocation allocation)	Returns the decision for where a shard should reside in the cluster.
Function<ShardRouting,ShardAllocationDecision>	explainShardAllocationFunction(RoutingAllocation allocation)	Similar to explainShardAllocation, but returns a Function that is more efficient for explaining many shards in a bulk circumstance.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.elasticsearch.cluster.routing.allocation.allocator.ShardsAllocator

allocate, execute

Field Details

SHARD_BALANCE_FACTOR_SETTING

public static final Setting<Float> SHARD_BALANCE_FACTOR_SETTING

INDEX_BALANCE_FACTOR_SETTING

public static final Setting<Float> INDEX_BALANCE_FACTOR_SETTING

WRITE_LOAD_BALANCE_FACTOR_SETTING

public static final Setting<Float> WRITE_LOAD_BALANCE_FACTOR_SETTING

DISK_USAGE_BALANCE_FACTOR_SETTING

public static final Setting<Float> DISK_USAGE_BALANCE_FACTOR_SETTING

THRESHOLD_SETTING

public static final Setting<Float> THRESHOLD_SETTING

INVALID_WEIGHTS_MINIMUM_LOG_INTERVAL

public static final Setting<TimeValue> INVALID_WEIGHTS_MINIMUM_LOG_INTERVAL

Constructor Details

BalancedShardsAllocator

public BalancedShardsAllocator()

BalancedShardsAllocator

public BalancedShardsAllocator(Settings settings)

BalancedShardsAllocator

public BalancedShardsAllocator(BalancerSettings balancerSettings,
 WriteLoadForecaster writeLoadForecaster)

BalancedShardsAllocator

@Inject
public BalancedShardsAllocator(BalancerSettings balancerSettings,
 WriteLoadForecaster writeLoadForecaster,
 BalancingWeightsFactory balancingWeightsFactory)

Method Details

allocate

public void allocate(RoutingAllocation allocation)

Description copied from interface: ShardsAllocator

Allocates shards to nodes in the cluster. An implementation of this method should: - assign unassigned shards - relocate shards that cannot stay on a node anymore - relocate shards to find a good shard balance in the cluster

Specified by:

allocate in interface ShardsAllocator

Parameters:

allocation - current node allocation

explainShardAllocation

public ShardAllocationDecision explainShardAllocation(ShardRouting shard,
 RoutingAllocation allocation)

Description copied from interface: ShardsAllocator

Returns the decision for where a shard should reside in the cluster. If the shard is unassigned, then the AllocateUnassignedDecision will be non-null. If the shard is not in the unassigned state, then the MoveDecision will be non-null. If an implementation of this interface does not support explaining decisions for a single shard through the cluster explain API, then this method should throw a UnsupportedOperationException.

Specified by:

explainShardAllocation in interface ShardsAllocator

explainShardAllocationFunction

public Function<ShardRouting,ShardAllocationDecision> explainShardAllocationFunction(RoutingAllocation allocation)

Description copied from interface: ShardsAllocator

Similar to explainShardAllocation, but returns a Function that is more efficient for explaining many shards in a bulk circumstance. Internally, an allocator builds up internal data structures for simulating its balancing algorithm. In some implementations, such as the BalancedShardsAllocator (also used within the DesiredBalanceAllocator), this internal context is computationally expensive. When run over many shards, it can be Order(shards * nodes). Instead of taking a shard and explaining it, explainShardAllocationFunction returns a Function that can be called repeatedly to explain multiple shards while reusing the context in the Function's closure. This reduces the computational cost of explain.

Specified by:

explainShardAllocationFunction in interface ShardsAllocator