Class SyncConsistentHashFactory

java.lang.Object

org.infinispan.distribution.ch.impl.SyncConsistentHashFactory

All Implemented Interfaces:

ConsistentHashFactory<DefaultConsistentHash>

Direct Known Subclasses:

TopologyAwareSyncConsistentHashFactory

@ProtoTypeId(1231)
public class SyncConsistentHashFactory
extends Object
implements ConsistentHashFactory<DefaultConsistentHash>

ConsistentHashFactory implementation that guarantees that multiple caches with the same members will have the same consistent hash (unlike DefaultConsistentHashFactory).

It has a drawback compared to DefaultConsistentHashFactory though: it can potentially move a lot more segments during a rebalance than strictly necessary. E.g. {0:AB, 1:BA, 2:CD, 3:DA} could turn into {0:BC, 1:CA, 2:CB, 3:AB} when D leaves, even though {0:AB, 1:BA, 2:CB, 3:AC} would require fewer segment ownership changes.

It may also reorder the owners of a segments, e.g. AB -> BA (same as DefaultConsistentHashFactory).

Since:

5.2

Author:

Dan Berindei

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	SyncConsistentHashFactory()

Method Summary

Modifier and Type	Method	Description
DefaultConsistentHash	create(int numOwners, int numSegments, List<Address> members, Map<Address,Float> capacityFactors)	Create a new consistent hash instance.
PersistedConsistentHash<DefaultConsistentHash>	fromPersistentState(ScopedPersistentState state, Function<UUID,Address> addressMapper)	Recreates a ConsistentHash from a previously stored persistent state.
static SyncConsistentHashFactory	getInstance()
DefaultConsistentHash	rebalance(DefaultConsistentHash baseCH)	Create a new consistent hash instance, based on an existing instance, but balanced according to the implementation's rules.
DefaultConsistentHash	union(DefaultConsistentHash ch1, DefaultConsistentHash ch2)	Creates a union of two compatible ConsistentHashes (use the same hashing function and have the same configuration parameters).
DefaultConsistentHash	updateMembers(DefaultConsistentHash baseCH, List<Address> newMembers, Map<Address,Float> actualCapacityFactors)	Updates an existing consistent hash instance to remove owners that are not in the newMembers list.

Methods inherited from class java.lang.Object

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

Constructor Details

SyncConsistentHashFactory

protected SyncConsistentHashFactory()

Method Details

getInstance

@ProtoFactory
public static SyncConsistentHashFactory getInstance()

create

public DefaultConsistentHash create(int numOwners,
 int numSegments,
 List<Address> members,
 Map<Address,Float> capacityFactors)

Description copied from interface: ConsistentHashFactory

Create a new consistent hash instance. The consistent hash will be balanced.

Specified by:

create in interface ConsistentHashFactory<DefaultConsistentHash>

Parameters:

numOwners - The ideal number of owners for each key. The created consistent hash can have more or less owners, but each key will have at least one owner.

numSegments - Number of hash-space segments. The implementation may round up the number of segments for performance, or may ignore the parameter altogether.

members - A list of addresses representing the new cache members.

capacityFactors - The capacity factor of each member. Determines the relative capacity of each node compared to the others. The implementation may ignore this parameter. If null, all the members are assumed to have a capacity factor of 1.

fromPersistentState

public PersistedConsistentHash<DefaultConsistentHash> fromPersistentState(ScopedPersistentState state,
 Function<UUID,Address> addressMapper)

Description copied from interface: ConsistentHashFactory

Recreates a ConsistentHash from a previously stored persistent state.

The stored state typically contains a collection of UUIDs representing the members. If a member is not present when reading from the state, its UUID must be added to the PersistedConsistentHash.missingUuids() list. The PersistedConsistentHash.consistentHash() may have incomplete ownership when there are missing UUIDs.

Specified by:

fromPersistentState in interface ConsistentHashFactory<DefaultConsistentHash>

Parameters:

state - the state to restore, containing member UUIDs.

addressMapper - A function to map the UUID to Address.

Returns:

A PersistedConsistentHash with the ConsistentHash and with the missing UUID if any.

updateMembers

public DefaultConsistentHash updateMembers(DefaultConsistentHash baseCH,
 List<Address> newMembers,
 Map<Address,Float> actualCapacityFactors)

Description copied from interface: ConsistentHashFactory

Updates an existing consistent hash instance to remove owners that are not in the newMembers list.

If a segment has at least one owner in newMembers, this method will not add another owner. This guarantees that the new consistent hash can be used immediately, without transferring any state.

If a segment has no owners in newMembers and the ConsistentHash implementation (e.g. DefaultConsistentHash) requires at least one owner for each segment, this method may add one or more owners for that segment. Since the data in that segment was lost, the new consistent hash can still be used without transferring state.

Specified by:

updateMembers in interface ConsistentHashFactory<DefaultConsistentHash>

Parameters:

baseCH - An existing consistent hash instance, should not be null

newMembers - A list of addresses representing the new cache members.

actualCapacityFactors - The capacity factor of each member. Determines the relative capacity of each node compared to the others. The implementation may ignore this parameter. If null, all the members are assumed to have a capacity factor of 1.

Returns:

A new ConsistentHash instance, or baseCH if the existing instance does not need any changes.

rebalance

public DefaultConsistentHash rebalance(DefaultConsistentHash baseCH)

Description copied from interface: ConsistentHashFactory

Create a new consistent hash instance, based on an existing instance, but balanced according to the implementation's rules.

Specified by:

rebalance in interface ConsistentHashFactory<DefaultConsistentHash>

Parameters:

baseCH - An existing consistent hash instance, should not be null

Returns:

A new ConsistentHash instance, or baseCH if the existing instance does not need any changes.

union

public DefaultConsistentHash union(DefaultConsistentHash ch1,
 DefaultConsistentHash ch2)

Description copied from interface: ConsistentHashFactory

Creates a union of two compatible ConsistentHashes (use the same hashing function and have the same configuration parameters).

The owners of a segment s in union(ch1, ch2) will include both the owners of s in ch1 and the owners of s in ch2, so a cache can switch from using union(ch1, ch2) to using ch2 without transferring any state.

Specified by:

union in interface ConsistentHashFactory<DefaultConsistentHash>