LWWRegister

Defined in: src/crdt/LWWRegister.ts:26

Last-Writer-Wins register. A single value with a timestamp; on merge the higher timestamp wins. Concurrent writes (same ts on two replicas) are resolved deterministically by replicaId lexicographic order — same input on every node, same winner.

Use this for single-value state that’s eventually consistent — a user’s display name, a feature-flag value, the latest-known health status of a service. When concurrent writes are common, pick a CRDT that captures both branches (e.g. an OR-Set of values) instead.

Wall-clock pitfall. Default timestamps come from Date.now(), which can drift between machines and even go backwards on the same machine (NTP correction). In practice this means a write from a faster-clocked node always wins; if that’s a problem, pass a clock option backed by a hybrid logical clock (HLC) or a Lamport counter.

const a = LWWRegister.empty().assign(‘a’, ‘red’); const b = LWWRegister.empty().assign(‘b’, ‘blue’); a.merge(b).value() // → whichever assign() was called later

Type Parameters

V

V

Implements

Crdt<LWWRegister<V>>

Methods

assign()

assign(replica, value, timestamp?): LWWRegister<V>

Defined in: src/crdt/LWWRegister.ts:44

Set the register to value, stamped with timestamp (default Date.now()) on behalf of replica. The timestamp is what merge uses to decide who wins — pass an explicit one if you want HLC/Lamport semantics.

Parameters

replica

string

value

V

timestamp?

number = ...

Returns

LWWRegister<V>

equals()

equals(other): boolean

Defined in: src/crdt/LWWRegister.ts:80

Parameters

other

LWWRegister<V>

Returns

boolean

merge()

merge(other): LWWRegister<V>

Defined in: src/crdt/LWWRegister.ts:54

Join two replicas. Must be a join-semilattice operation: total, idempotent, commutative, associative.

Parameters

other

LWWRegister<V>

Returns

LWWRegister<V>

Implementation of

Crdt.merge

timestamp()

timestamp(): number

Defined in: src/crdt/LWWRegister.ts:52

Timestamp of the last write — 0 for an empty register.

Returns

number

toJSON()

toJSON(): LWWRegisterJson<V>

Defined in: src/crdt/LWWRegister.ts:66

Wire-friendly representation — every CRDT must be JSON-encodable so it can travel through the cluster transport without bespoke codecs. toJSON() is the inverse of the static fromJSON factory each impl exposes.