Package me.ahoo.cosid.internal

Class TimestampSequencer

java.lang.Object

me.ahoo.cosid.internal.TimestampSequencer

public final class TimestampSequencer
extends Object

The timestamp and sequence logic shared by the snowflake and CosId generators.

Internal: not part of the CosId API, it may change in any release.

Within one time unit the sequence increments; when it wraps around, next() waits for the next time unit. When a new time unit starts and the sequence has passed sequenceResetThreshold, it restarts from 1, which keeps low-traffic ids from all ending in the same sequence values. A clock that moved backwards throws ClockBackwardsException. Not thread-safe: callers synchronize.

Constructor Summary

Constructors

Constructor	Description
TimestampSequencer(LongSupplier timeSource, long maxSequence, long sequenceResetThreshold)	Create a sequencer.

Method Summary

Modifier and Type	Method	Description
long	getLastTimestamp()
long	getSequence()
long	next()	Advance to the next (timestamp, sequence) pair; read it with getLastTimestamp() and getSequence().

Methods inherited from class java.lang.Object

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

Constructor Details

TimestampSequencer

public TimestampSequencer(LongSupplier timeSource,
 long maxSequence,
 long sequenceResetThreshold)

Create a sequencer.

Parameters:

timeSource - current time in the generator's unit (milliseconds or seconds)

maxSequence - largest sequence, a power of two minus one

sequenceResetThreshold - sequences at or above this restart in the next time unit

Method Details

next

public long next()

Advance to the next (timestamp, sequence) pair; read it with getLastTimestamp() and getSequence().

Returns:

the timestamp of the new pair

Throws:

ClockBackwardsException - if the clock moved back behind the last timestamp

getSequence

public long getSequence()

getLastTimestamp

public long getLastTimestamp()