antonkharenko / logical-clocks

Lamport and Vector clocks

Logical Clocks

Java implementation of Lamport and Vector logical clocks. This repository serves as an illustration to blog post Time, Clocks and Ordering in a Distributed System.

How to use

// 
// Logical Timestamp
// 

// Initialize
LogicalTimestamp ts0 = new LogicalTimestamp();
LogicalTimestamp ts1 = ts0.nextTimestamp();
LogicalTimestamp ts100 = LogicalTimestamp.fromLong(100L);

// Serialize and deserialize
byte[] ts0AsBytes = ts0.toBytes();
LogicalTimestamp deserializedTs0 = LogicalTimestamp.fromBytes(ts0AsBytes);
long ts1AsLong = ts1.asLong();
LogicalTimestamp deserializedTs1 = LogicalTimestamp.fromLong(ts1AsLong);

// Compare
ts0.isBefore(ts1); // true
ts1.isAfter(ts0); // true
ts0.compareTo(ts1); // < 0
ts1.compareTo(ts0); // > 0
ts0.equals(ts1); // false
ts0.isAfter(ts1); //false
ts1.isBefore(ts1); // false

// 
// Logical Clock (thread-safe)
// 

// Initialize
LogicalTimestamp initialTimestamp = new LogicalTimestamp();
LogicalClock clock = new LogicalClock(initialTimestamp);

// Time & tick
LogicalTimestamp currentTs = clock.time();
LogicalTimestamp nextTs = clock.tick(); // thread-safe
LogicalTimestamp newCurrentTs = clock.time(); // happens after currentTs

See Unit tests for more examples.