com.hazelcast.config

Class FlakeIdGeneratorConfig

java.lang.Object

com.hazelcast.config.FlakeIdGeneratorConfig

All Implemented Interfaces:

NamedConfig, DataSerializable, IdentifiedDataSerializable

public class FlakeIdGeneratorConfig
extends Object
implements IdentifiedDataSerializable, NamedConfig

The FlakeIdGeneratorConfig contains the configuration for the member regarding Flake ID Generator.

Since:

3.10

Field Summary

Fields

Modifier and Type	Field and Description
static long	DEFAULT_ALLOWED_FUTURE_MILLIS Default value for getAllowedFutureMillis().
static int	DEFAULT_BITS_NODE_ID Default value for getBitsNodeId().
static int	DEFAULT_BITS_SEQUENCE Default value for getBitsSequence().
static long	DEFAULT_EPOCH_START Default value for getEpochStart().
static int	DEFAULT_PREFETCH_COUNT Default value for getPrefetchCount().
static long	DEFAULT_PREFETCH_VALIDITY_MILLIS Default value for getPrefetchValidityMillis().
static int	MAXIMUM_PREFETCH_COUNT Maximum value for prefetch count.

Constructor Summary

Constructors

Constructor and Description
FlakeIdGeneratorConfig()
FlakeIdGeneratorConfig(FlakeIdGeneratorConfig other) Copy-constructor
FlakeIdGeneratorConfig(String name)

Method Summary

Modifier and Type	Method and Description
boolean	equals(Object o)
long	getAllowedFutureMillis()
int	getBitsNodeId()
int	getBitsSequence()
int	getClassId() Returns type identifier for this class.
long	getEpochStart()
int	getFactoryId() Returns DataSerializableFactory factory ID for this class.
String	getName() Returns the configuration name.
long	getNodeIdOffset()
int	getPrefetchCount()
long	getPrefetchValidityMillis()
int	hashCode()
boolean	isStatisticsEnabled()
void	readData(ObjectDataInput in) Reads fields from the input stream
FlakeIdGeneratorConfig	setAllowedFutureMillis(long allowedFutureMillis) Sets how far to the future is the generator allowed to go to generate IDs without blocking.
FlakeIdGeneratorConfig	setBitsNodeId(int bitsNodeId) Sets the bit-length of node id component.
FlakeIdGeneratorConfig	setBitsSequence(int bitsSequence) Sets the bit-length of the sequence component.
FlakeIdGeneratorConfig	setEpochStart(long epochStart) Sets the offset of timestamp component in milliseconds.
FlakeIdGeneratorConfig	setName(String name) Sets the name or name pattern for this config.
FlakeIdGeneratorConfig	setNodeIdOffset(long nodeIdOffset) Sets the offset that will be added to the node ID assigned to cluster member for this generator.
FlakeIdGeneratorConfig	setPrefetchCount(int prefetchCount) Sets how many IDs are pre-fetched on the background when one call to FlakeIdGenerator.newId() is made.
FlakeIdGeneratorConfig	setPrefetchValidityMillis(long prefetchValidityMs) Sets for how long the pre-fetched IDs can be used.
FlakeIdGeneratorConfig	setStatisticsEnabled(boolean statisticsEnabled) Enables or disables statistics gathering of LocalFlakeIdGeneratorStats.
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

Field Detail

DEFAULT_PREFETCH_COUNT

public static final int DEFAULT_PREFETCH_COUNT

Default value for getPrefetchCount().

See Also:

Constant Field Values

DEFAULT_PREFETCH_VALIDITY_MILLIS

public static final long DEFAULT_PREFETCH_VALIDITY_MILLIS

Default value for getPrefetchValidityMillis().

See Also:

Constant Field Values

DEFAULT_EPOCH_START

public static final long DEFAULT_EPOCH_START

Default value for getEpochStart(). 1514764800000 is the value System.currentTimeMillis() would return on 1.1.2018 0:00 UTC.

See Also:

Constant Field Values

DEFAULT_BITS_SEQUENCE

public static final int DEFAULT_BITS_SEQUENCE

Default value for getBitsSequence().

See Also:

Constant Field Values

DEFAULT_BITS_NODE_ID

public static final int DEFAULT_BITS_NODE_ID

Default value for getBitsNodeId().

See Also:

Constant Field Values

DEFAULT_ALLOWED_FUTURE_MILLIS

public static final long DEFAULT_ALLOWED_FUTURE_MILLIS

Default value for getAllowedFutureMillis().

See Also:

Constant Field Values

MAXIMUM_PREFETCH_COUNT

public static final int MAXIMUM_PREFETCH_COUNT

Maximum value for prefetch count. The limit is ~10% of the default time we allow the IDs to be from the future (see DEFAULT_ALLOWED_FUTURE_MILLIS).

The reason to limit the prefetch count is that a single call to FlakeIdGenerator.newId() might be blocked if the future allowance is exceeded: we want to avoid a single call for a large batch to block another call for a small batch.

See Also:

Constant Field Values

Constructor Detail

FlakeIdGeneratorConfig

public FlakeIdGeneratorConfig()

FlakeIdGeneratorConfig

public FlakeIdGeneratorConfig(String name)

FlakeIdGeneratorConfig

public FlakeIdGeneratorConfig(FlakeIdGeneratorConfig other)

Copy-constructor

Method Detail

getName

public String getName()

Returns the configuration name. This can be actual object name or pattern.

Specified by:

getName in interface NamedConfig

setName

public FlakeIdGeneratorConfig setName(String name)

Sets the name or name pattern for this config. Must not be modified after this instance is added to Config.

Specified by:

setName in interface NamedConfig

getPrefetchCount

public int getPrefetchCount()

See Also:

setPrefetchCount(int)

setPrefetchCount

public FlakeIdGeneratorConfig setPrefetchCount(int prefetchCount)

Sets how many IDs are pre-fetched on the background when one call to FlakeIdGenerator.newId() is made. Default is 100.

This setting pertains only to newId() calls made on the member that configured it.

Parameters:

prefetchCount - the desired prefetch count, in the range 1..100000.

Returns:

this instance for fluent API

getPrefetchValidityMillis

public long getPrefetchValidityMillis()

See Also:

setPrefetchValidityMillis(long)

setPrefetchValidityMillis

public FlakeIdGeneratorConfig setPrefetchValidityMillis(long prefetchValidityMs)

Sets for how long the pre-fetched IDs can be used. If this time elapses, a new batch of IDs will be fetched. Time unit is milliseconds, default is 600,000 (10 minutes).

The IDs contain timestamp component, which ensures rough global ordering of IDs. If an ID is assigned to an object that was created much later, it will be much out of order. If you don't care about ordering, set this value to 0.

This setting pertains only to newId calls made on the member that configured it.

Parameters:

prefetchValidityMs - the desired ID validity or unlimited, if <=0

Returns:

this instance for fluent API

setEpochStart

public FlakeIdGeneratorConfig setEpochStart(long epochStart)

Sets the offset of timestamp component in milliseconds. By default it's 1514764800000L, that is the beginning of 2018. You can adjust the value to determine the lifespan of the generator. See FlakeIdGenerator's class javadoc for more information.

Note: If you set the epoch start to a future instant, negative IDs will be generated until that time occurs.

Parameters:

epochStart - the desired epoch start

Returns:

this instance for fluent API

Since:

4.0

getEpochStart

public long getEpochStart()

See Also:

setEpochStart(long)

getNodeIdOffset

public long getNodeIdOffset()

See Also:

setNodeIdOffset(long)

setNodeIdOffset

public FlakeIdGeneratorConfig setNodeIdOffset(long nodeIdOffset)

Sets the offset that will be added to the node ID assigned to cluster member for this generator. Might be useful in A/B deployment scenarios where you have cluster A which you want to upgrade. You create cluster B and for some time both will generate IDs and you want to have them unique. In this case, configure node ID offset for generators on cluster B.

Parameters:

nodeIdOffset - the value added to the node id

Returns:

this instance for fluent API

See Also:

for the node id logic

getBitsSequence

public int getBitsSequence()

See Also:

setBitsSequence(int)

setBitsSequence

public FlakeIdGeneratorConfig setBitsSequence(int bitsSequence)

Sets the bit-length of the sequence component. This setting determines the maximum rate at which IDs can be generated. See FlakeIdGenerator's class javadoc for more information.

Parameters:

bitsSequence - sequence component bit-length

Returns:

this instance for fluent API

Since:

4.0

getBitsNodeId

public int getBitsNodeId()

See Also:

setBitsNodeId(int)

setBitsNodeId

public FlakeIdGeneratorConfig setBitsNodeId(int bitsNodeId)

Sets the bit-length of node id component. See FlakeIdGenerator's class javadoc for more information.

Parameters:

bitsNodeId - node id component bit-length

Returns:

this instance for fluent API

Since:

4.0

getAllowedFutureMillis

public long getAllowedFutureMillis()

See Also:

setAllowedFutureMillis(long)

setAllowedFutureMillis

public FlakeIdGeneratorConfig setAllowedFutureMillis(long allowedFutureMillis)

Sets how far to the future is the generator allowed to go to generate IDs without blocking.

The number of bits configured for the sequence number (setBitsSequence(int) determines how many IDs can be generated per second. We allow the generator to generate IDs with future timestamps, and this settings limits how much. When more IDs are requested, the call will block. This is important in case of a cluster black-out or cluster restart: we don't store how far the members went and after they restart, they will start from current time. If before the restart the generator went beyond the current time, duplicate IDs could be generated.

The default value is 15 seconds (15000). If your cluster is able to restart more quickly, set a lower value.

See FlakeIdGenerator's class javadoc for more information.

Parameters:

allowedFutureMillis - value in milliseconds

Returns:

this instance for fluent API

Since:

4.0

isStatisticsEnabled

public boolean isStatisticsEnabled()

See Also:

setStatisticsEnabled(boolean)

setStatisticsEnabled

public FlakeIdGeneratorConfig setStatisticsEnabled(boolean statisticsEnabled)

Enables or disables statistics gathering of LocalFlakeIdGeneratorStats.

Parameters:

statisticsEnabled - true if statistics gathering is enabled (which is also the default), false otherwise

Returns:

this instance for fluent API

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

getClassId

public int getClassId()

Description copied from interface: IdentifiedDataSerializable

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

Specified by:

getClassId in interface IdentifiedDataSerializable

Returns:

type ID

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.