Copyright © 2023 Anuar Alfetahe

Version: 0.2.1

Authors: Anuar Alfetahe (anuar.alfetahe@gmail.com).

Elector is an Erlang application that automatically detects all nodes inside the distributed Erlang cluster and chooses the leader node. The elections are started automatically when the Elector application is started or when a node joins or leaves the cluster. Elector also allows you to run pre- and post-election hooks that will be triggered when the election process is started and finished.

The default election strategy is to choose the node with the highest runtime.

Installation for Elixir application

Add {:elector, "~> 0.2.1"}` under the deps in the `mix.exs` file: ``` defp deps do [ {:elector, "~> 0.2.1"} ] end''

Next add elector under the extra_applications in the mix.exs file:
  def application do
      extra_applications: [:elector],
      mod: {MyApp, []}

Installation for Erlang application

Add elector to the deps in the rebar.config file: {deps, [{elector, {"elector", "0.2.1"}]}. Next add elector` to the `applications` list in the `myapp.app.src file: {applications, [elector]}.


Start election manually

Elixir: :elector.elect_sync() or :elector.elect()

Erlang: elector:elect_sync() or elector:elect()

Get current leader

> alias :elector, as Elector
> Elector.get_leader()
{:ok, :example_node}
> elector:get_leader().
{ok, example_node}

See the elector module for more.

Elector supports the following configurations:

election_delay - The delay in milliseconds before the new election starts. This value is used automatic election is triggered either by node join/leave or startup. Default value is 1 second(1000).

sync_start - If true the election will start synchronously on start up. Set it false if start up should be async. Default value is true.

strategy_module - The module that is used for the election strategy implementation. Available options are: runtime_high_strategy` and `runtime_low_strategy. Feel free to write your own strategy module that implements the strategy_behaviour module. Default value is runtime_high_strategy which chooses the node with the highest runtime.

pre_election_hooks - A list of hooks/function calls that will be triggered before the node is starting the election. Expects a list of tuples with the following format: {Module, Function, Args}. Default value is [].

post_election_hooks - A list of hooks/function calls that will be triggered after the election process. Expects a list of tuples with the following format: {Module, Function, Args}. Default value is [].

startup_hooks_enabled- If true the pre_election_hooks and post_election_hooks will be triggered on startup. Default value is true.

quorum_size - The number of nodes(including the local node) that should be available in the cluster before the election process is started. D o not set it to 0 as it will disable the election process, leave empty or 1 if you want to run the election process even if there are no other nodes in the cluster. Default value is 1.

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