Class RackAwarePlacement

java.lang.Object

com.loomcache.server.cluster.RackAwarePlacement

public class RackAwarePlacement
extends Object

Ensures partition replicas are distributed across racks for fault tolerance.

Strategy:

• Respects placement constraints (min racks, max replicas per rack)
• Validates existing placements
• Suggests optimal placement for new partitions

Thread safety: uses ReentrantLock for cluster topology access.

Since:

1.0

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static interface	RackAwarePlacement.ClusterTopology	Represents the cluster topology for placement calculations.
static final record	RackAwarePlacement.PlacementConstraint	Constraints for rack-aware placement.
static class	RackAwarePlacement.SimpleClusterTopology	Simple implementation of ClusterTopology.

Constructor Summary

Constructors

Constructor	Description
RackAwarePlacement(RackAwarePlacement.ClusterTopology clusterTopology)	Create a new RackAwarePlacement with default constraints.
RackAwarePlacement(RackAwarePlacement.ClusterTopology clusterTopology, RackAwarePlacement.PlacementConstraint constraint)	Create a new RackAwarePlacement with specified constraints.

Method Summary

Modifier and Type	Method	Description
List<String>	suggestPlacement(String partitionId, int replicaCount)	Suggest an optimal placement for a new partition.
boolean	validatePlacement(String partitionId, List<String> replicas)	Validate that a partition's replica placement respects constraints.

Methods inherited from class Object

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

Constructor Details

RackAwarePlacement

public RackAwarePlacement(RackAwarePlacement.ClusterTopology clusterTopology)

Create a new RackAwarePlacement with default constraints.

Parameters:

clusterTopology - the cluster topology information

RackAwarePlacement

public RackAwarePlacement(RackAwarePlacement.ClusterTopology clusterTopology,
 RackAwarePlacement.PlacementConstraint constraint)

Create a new RackAwarePlacement with specified constraints.

Parameters:

clusterTopology - the cluster topology information

constraint - the placement constraints to enforce

Method Details

validatePlacement

public boolean validatePlacement(String partitionId,
 List<String> replicas)

Validate that a partition's replica placement respects constraints.

Parameters:

partitionId - the partition ID

replicas - list of node IDs that hold this partition's replicas

Returns:

true if placement is valid, false otherwise

Throws:

IllegalArgumentException - if parameters are invalid

suggestPlacement

public List<String> suggestPlacement(String partitionId,
 int replicaCount)

Suggest an optimal placement for a new partition.

Algorithm:

1. Identify available racks
2. Distribute replicas across racks to minimize failure correlation
3. Respect maxReplicasPerRack constraint

Parameters:

partitionId - the partition ID

replicaCount - desired number of replicas

Returns:

list of node IDs for the replicas, or empty list if placement impossible

Throws:

IllegalArgumentException - if parameters are invalid