Laymer / braid

Erlang library to create and connect an arbitrary cluster of nodes

braid

Braid is an Erlang library to create and connect an arbitrary cluster of nodes. The library is intended to be used for testing. It works in a similar mode to slave, where nodes set up through the library are linked to the process creating the cluster. Once that process terminates, all the nodes are cleaned up.

Model

Braid starts a manager process on the current node, which in turn is responsible for setting up the cluster. The nodes started in the cluster connects back to the current node via hidden node connections. If you want to connect additional managing nodes to the cluster, it might be a good idea to make those nodes hidden as well to prevent the test cluster from seeing unexpected new normal nodes. This all depends on what you are testing of course.

Example

Given the following configuriation:

Nodes = #{
    n1 => #{
        args => [{connect_all, false}],
        connections => [n4, n2]
    },
    n2 => #{
        args => [{connect_all, false}],
        connections => [n1, n3]
    },
    n3 => #{
        args => [{connect_all, false}],
        connections => [n2, n4]
    },
    n4 => #{
        args => [{connect_all, false}],
        connections => [n3, n1]
    }
}.

You can create a cluster with:

(manager@host)1> Cluster = braid:create(Nodes).
<0.87.0>

To check the cluster connections:

(manager@host)2> braid:multicall(Cluster, erlang, nodes, []).
#{n1 => ['n4@host','n2@host'],
  n2 => ['n1@host','n3@host'],
  n3 => ['n2@host','n4@host'],
  n4 => ['n1@host','n3@host']}
(manager@host)3> braid:multicall(Cluster, erlang, nodes, [hidden]).
#{n1 => ['manager@host'],
  n2 => ['manager@host'],
  n3 => ['manager@host'],
  n4 => ['manager@host']}

Roadmap

• Support starting nodes on remote hosts
• Allow custom erl command line flags