NodeRegistry

A simple node registry built on top of the Erlang :global module

Installation

def deps do
  [
    {:node_registry, "~> 0.1"},
    # or
    {:node_registry, github: "antonmi/node_registry"}
  ]
end

Motivation

Assuming:

• you have a cluster of nodes;
• different services are running on different nodes;
• some nodes may run identical services;
• some nodes may run different versions of the same service;
• you want to find a node with a specific service and do, for example, rpc.call to it.

Solution

NodeRegistry provides a simple way to register node with a specific name.

It uses Erlang's :global module to register a node with a specific name. It then uses :global.whereis_name to find a node by name. Or it queries the :global_names ETS table to search nodes by name prefix.

Usage

Add {NodeRegistry, :my_service} to the end of supervisor's children list.

Name is any arbitrary atom or string.

Examples:

:my_service ("my_service"), if you have only one "instance" of the service

:my_service_v1 ("my_service_v1"), if you have multiple versions of the same service

"web_service_v1_#{postfix}", if you have multiple versions / instances of the same service

Then you can find it and do rpc.call like:

:my_service
|> NodeRegistry.node_with_name()
|> :rpc.call(Module, function, args)

If you have services with identical functionality on different nodes, you can register them with the same prefix:

{NodeRegistry, :my_service_1} # on node1
{NodeRegistry, :my_service_2} # on node2

Then you can find them and do rpc.call like:

:my_service
|> NodeRegistry.random_node_with_prefix()
|> :rpc.call(Module, function, args)

# or

:my_service
|> NodeRegistry.nodes_with_prefix()
|> :rpc.multicall(Module, function, args)

NodeRegistry.Remote

One can import NodeRegistry.Remote and call remotely any function on random node with a specific name prefix.

defmodule MyApp do
  import NodeRegistry.Remote
    
  def call_my_service do
    remote(:my_service, Mod, :fun, [1,2])
  end
end