lattice_crdt

Umbrella package for Lattice CRDTs: counters, registers, sets, maps, and causal core types.

Install this package when you want the full Lattice CRDT toolkit. For smaller dependency graphs, install the individual packages directly.

Installation

gleam add lattice_crdt

Packages included

Package	Provides
`lattice_core`	Replica IDs, version vectors, and dot contexts.
`lattice_counters`	Grow-only and positive-negative counters.
`lattice_registers`	Last-writer-wins and multi-value registers.
`lattice_sets`	Grow-only, two-phase, and observed-remove sets.
`lattice_maps`	Last-writer-wins maps, observed-remove maps, and CRDT dispatch.
`lattice_sequence`	Generic sequence CRDT using YATA-style left/right origins.
`lattice_text`	Plain-text CRDT backed by `lattice_sequence`.

Quick example

import lattice_core/replica_id
import lattice_counters/g_counter

pub fn main() {
  let assert Ok(counter) =
    g_counter.new(replica_id.new("node-a"))
    |> g_counter.increment(1)

  g_counter.value(counter)
  // -> 1
}

Notes

This package reuses the public modules from the individual Lattice packages.
Import modules from their package-specific paths, such as lattice_counters/g_counter or lattice_sets/or_set.
All CRDT packages support deterministic merge semantics and JSON serialization.
Many mutators also expose delta-state variants for efficient incremental replication.

Delta-state replication

Leaf CRDTs expose op_with_delta alongside their state-only operations. Infallible operations return a state or #(state, delta). Fallible operations return Result around the state or tuple. The delta has the same CRDT type as the state and uses the same merge function.

Sequence and text merges require merge(a, b, local_id) to select the identity for later edits. merge_as remains an equivalent alias. Counter, sequence, and text edits now return Result under their plain names; remove the former try_ prefix when upgrading, except for the distinct try_substring API.

ORMapDelta(a) represents changed map keys. CrdtDelta(a) keeps nested ORMap changes separate from leaf state deltas, so a small Text or Sequence edit need not send the whole child.

Sparse replication requires a baseline or eventual delivery of the required deltas. Reordered and duplicate messages converge after that history arrives. One later delta cannot reconstruct an arbitrary empty receiver. See DEV.md and examples/src/or_map_delta_websocket_example.gleam.

Typed map composition

The umbrella exports Crdt(a), CrdtSpec(a), CrdtDelta(a), ORMap(a), ORMapDelta(a), and LWWMap(a). Both map types support recursive CRDT children. A map uses one child specification; applications can use a tagged payload union for mixed data.

ORMap joins concurrent child edits. After removal, a re-add starts a fresh generation; the newest generation wins over older histories. Concurrent update/removal within one generation remains add-wins. LWWMap instead selects one complete child assignment by timestamp and writer.

Use the receiving writer’s identity when adopting a snapshot. Map key pruning does not authorize compaction of child Sequence/Text history. Upgrading existing maps requires explicit legacy import and a coordinated switch to the new protocol; see the root README migration guide.

Reference: Almeida, Shoker, Baquero — Delta State Replicated Data Types.

License

MIT

lattice_crdt - v4.0.0