com.hazelcast.cluster.impl

Class VectorClock

java.lang.Object

com.hazelcast.cluster.impl.VectorClock

All Implemented Interfaces:

DataSerializable, IdentifiedDataSerializable

public class VectorClock
extends Object
implements IdentifiedDataSerializable

Vector clock consisting of distinct replica logical clocks.

See https://en.wikipedia.org/wiki/Vector_clock The vector clock may be read from different thread but concurrent updates must be synchronized externally. There is no guarantee for concurrent updates.

Constructor Summary

Constructors

Constructor and Description
VectorClock()
VectorClock(VectorClock from)

Method Summary

Modifier and Type	Method and Description
Set<Map.Entry<String,Long>>	entrySet() Returns a set of replica logical timestamps for this vector clock.
boolean	equals(Object o)
int	getFactoryId() Returns DataSerializableFactory factory ID for this class.
int	getId() Returns type identifier for this class.
Long	getTimestampForReplica(String replicaId) Returns logical timestamp for given replicaId.
int	hashCode()
boolean	isAfter(VectorClock other) Returns true if this vector clock is causally strictly after the provided vector clock.
boolean	isEmpty() Returns true if this vector clock is empty (there are no logical timestamps for any replica).
void	merge(VectorClock other) Merges the provided vector clock into this one by taking the maximum of the logical timestamps for each replica.
void	readData(ObjectDataInput in) Reads fields from the input stream
void	setReplicaTimestamp(String replicaId, long timestamp) Sets the logical timestamp for the given replicaId.
String	toString()
void	writeData(ObjectDataOutput out) Writes object fields to output stream

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

VectorClock

public VectorClock()

VectorClock

public VectorClock(VectorClock from)

Method Detail

getTimestampForReplica

public Long getTimestampForReplica(String replicaId)

Returns logical timestamp for given replicaId. This method may be called from different threads and the result reflects the latest update on the vector clock.

setReplicaTimestamp

public void setReplicaTimestamp(String replicaId,
                                long timestamp)

Sets the logical timestamp for the given replicaId. This method is not thread safe and concurrent access must be synchronized externally.

merge

public void merge(VectorClock other)

Merges the provided vector clock into this one by taking the maximum of the logical timestamps for each replica. This method is not thread safe and concurrent access must be synchronized externally.

isAfter

public boolean isAfter(VectorClock other)

Returns true if this vector clock is causally strictly after the provided vector clock. This means that it the provided clock is neither equal to, greater than or concurrent to this vector clock. This method may be called from different threads and the result reflects the latest update on the vector clock.

isEmpty

public boolean isEmpty()

Returns true if this vector clock is empty (there are no logical timestamps for any replica). This method may be called from different threads and the result reflects the latest update on the vector clock.

entrySet

public Set<Map.Entry<String,Long>> entrySet()

Returns a set of replica logical timestamps for this vector clock.

writeData

public void writeData(ObjectDataOutput out)
               throws IOException

Description copied from interface: DataSerializable

Writes object fields to output stream

Specified by:

writeData in interface DataSerializable

Parameters:

out - output

Throws:

IOException - if an I/O error occurs. In particular, an IOException may be thrown if the output stream has been closed.

readData

public void readData(ObjectDataInput in)
              throws IOException

Description copied from interface: DataSerializable

Reads fields from the input stream

Specified by:

readData in interface DataSerializable

Parameters:

in - input

Throws:

IOException - if an I/O error occurs. In particular, an IOException may be thrown if the input stream has been closed.

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object

getFactoryId

public int getFactoryId()

Description copied from interface: IdentifiedDataSerializable

Returns DataSerializableFactory factory ID for this class.

Specified by:

getFactoryId in interface IdentifiedDataSerializable

Returns:

factory ID

getId

public int getId()

Description copied from interface: IdentifiedDataSerializable

Returns type identifier for this class. It should be unique per DataSerializableFactory.

Specified by:

getId in interface IdentifiedDataSerializable

Returns:

type ID