Lasp

Overview

Lasp is a programming model for synchronization-free computations.

Installing

Lasp requires Erlang 19 or greater. Once you have Erlang installed, do the following to install and build Lasp.

$ git clone git@github.com:lasp-lang/lasp.git
$ cd lasp
$ make

Creating a small cluster

Clone Lasp:

$ git clone https://github.com/lasp-lang/lasp.git

Run two shells

$ rebar3 shell --name a@127.0.0.1
$ rebar3 shell --name b@127.0.0.1

Exceute to node a:

1> lasp_peer_service:join('a@127.0.0.1').
ok
2> lasp_peer_service:members().
{ok,['a@127.0.0.1','b@127.0.0.1']}

Execute node b:

1> lasp_peer_service:members().
{ok,['a@127.0.0.1','b@127.0.0.1']}

Go back to node a and run:

3> Content = #{what => i_am_an_awmap_value}.

% create a lasp CRDT
AwMapVarName = <<"awmap">>.
Key1 = <<"key1">>.
AwMapType = {state_awmap, [state_mvregister]}.
{ok, {AwMap, _, _, _}} = lasp:declare({AwMapVarName, AwMapType}, AwMapType).


% Update the CRDT with the content
{ok, _} = lasp:update(AwMap, {apply, Key1, {set, nil, Content}}, term_to_binary(node())).

Go to node b and retrieve the content of the CRDT:

2> {ok,[{_, AwMapSet}]} = lasp:query({<<"awmap">>,{state_awmap,[state_mvregister]}}).

3> sets:to_list(AwMapSet).
% [#{what => i_am_an_awmap_value}]

If you try to make a cluster with remote nodes and face an error related to connection attempts from disallowed nodes, you may simply need to put the same erlang.cookie on the machines beforehand to allow them to communicate.

Running a shell

You can run a Erlang shell where you can interact with a Lasp node by doing the following:

$ make shell

Running the test suite

To run the test suite, which will execute all of the Lasp scenarios, use the following command.

$ make check

Code examples

This blog post by @marianoguerra contains concise sample code.