lattice_counters

Grow-only and positive-negative CRDT counters for Gleam.

Use this package when replicas need to count events independently and merge without coordination. Choose g_counter for counters that only increase, or pn_counter when values can increase and decrease.

Installation

gleam add lattice_counters

Quick example

import lattice_core/replica_id
import lattice_counters/g_counter

pub fn main() {
  let assert Ok(node_a) =
    g_counter.new(replica_id.new("node-a"))
    |> g_counter.increment(2)

  let assert Ok(node_b) =
    g_counter.new(replica_id.new("node-b"))
    |> g_counter.increment(3)

  let merged = g_counter.merge(node_a, node_b)

  g_counter.value(merged)
  // -> 5
}

Modules

Module	Purpose
`lattice_counters/g_counter`	Grow-only counter. Merges by taking the maximum count per replica.
`lattice_counters/pn_counter`	Positive-negative counter built from two grow-only counters.

Notes

Both counters expose new, merge, value, to_json, and from_json.
Use increment_with_delta and decrement_with_delta when you want to replicate only the delta from an operation.
increment, decrement, and their _with_delta variants return Result. Negative deltas return Error(NegativeDelta(delta)); zero is accepted. The former try_* names have been removed.
PNCounter computes its value as positive counts minus negative counts.

License