org.terracotta.management.sequence
Class BoundaryFlakeSequenceGenerator

java.lang.Object
  org.terracotta.management.sequence.BoundaryFlakeSequenceGenerator

All Implemented Interfaces:

SequenceGenerator

public final class BoundaryFlakeSequenceGenerator
extends Object
implements SequenceGenerator

Sort of Boundary Flake, inspired by (and related docs):

• http://www.slideshare.net/davegardnerisme/unique-id-generation-in-distributed-systems
• https://github.com/mumrah/flake-java
• https://github.com/boundary/flake
• https://github.com/rholder/fauxflake
• https://github.com/hibernate/hibernate-orm/blob/master/hibernate-testing/src/main/java/org/hibernate/testing/cache/Timestamper.java

For this implementation we will use:

 SEQUENCE = TIMESTAMP + NODE_ID + SEQUENCE_ID
 NODE_ID = MAC + PID
 SEQUENCE_ID = CLASSLOADER_ID + INSTANCE_ID + SEQUENCE_MS
 

Where:

• TIMESTAMP: 46 bits - enough for next >200 years
• MAC: 48 bits - full mac address
• PID: 16 bits - latest bits of the PID / VMID
• CLASSLOADER_ID: 32 bits - classloader hashcode
• INSTANCE_ID: 14 bits - number of instances per classloader
• SEQUENCE_MS: 18 bits - seq id within the same millisecond

This leads to 3 longs (192 bits).

This generator will generate a maximum of about 262,144 sequence numbers / millisecond / instance / classloader / JVM / machine, with high probability to be unique if node id is unique.

Author:

Mathieu Carbou

Constructor Summary

BoundaryFlakeSequenceGenerator()

BoundaryFlakeSequenceGenerator(TimeSource timeSource, NodeIdSource nodeIdSource)

Method Summary

TimeSource	getTimeSource()
Sequence	next()

Methods inherited from class java.lang.Object

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

Constructor Detail

BoundaryFlakeSequenceGenerator

public BoundaryFlakeSequenceGenerator()

BoundaryFlakeSequenceGenerator

public BoundaryFlakeSequenceGenerator(TimeSource timeSource,
                                      NodeIdSource nodeIdSource)

Method Detail

getTimeSource

public TimeSource getTimeSource()

Specified by:

getTimeSource in interface SequenceGenerator

next

public Sequence next()

Specified by:

next in interface SequenceGenerator