bobbynarvy / crdt_simulator

Simulates several CRDTs using Elixir processes as replicas

CRDTSimulator

This project simulates several CRDTs using Elixir processes as replicas that hold and share state with each other, and eventually merge to a single consistent state.

Usage

Upon starting an iex session with this project (iex -S mix), start by creating a cluster of replicas:

# Create a cluster of 3 Positive-Negative Counter replicas
CRDTSimulator.start_link({:pn_counter, 3})

Note: CRDT identifiers can be chosen from the implemented varieties.

Several internal processes will be launched that essentially watch over replica updates and broadcast them to other replicas.

Specific replica pids can be accessed by index and updated:

replica_0 = CRDT.Registry.replicas(0)
CRDT.Replica.update(replica_0, {:increment})

The user is prompted when updates have been propagated throughout the cluster.

Update broadcast delays to specific replicas can be simulated:

# The next update to the first replica will appear after 3 seconds
# once the next update to another replica is triggered
CRDT.ReplicaBroadcaster.delay(0, 3000)

Update broadcast failures can also be simulated:

# The next update to the first replica will fail. Any new updates
# will only be applied upon merge of a new update
CRDT.ReplicaBroadcaster.fail(0)

CRDT Varieties

CRDT	Identifier	Update operation(s)
Grow-only Counter (G-Counter)	:g_counter	{:increment}
Positive-Negative Counter (Counter)	:pn_counter	{:increment}, {:decrement}
Grow-only Set (G-set)	:g_set	{:add, *element*}
Two-phase Set (TP-set)	:tp_set	{:add, *element*}, {:remove, *element*}