Mnesiam

Mnesiam makes clustering easy for Mnesia database.

The module docs can be found at https://hexdocs.pm/mnesiam.

Installation

The package can be installed by adding mnesiam to your list of dependencies in mix.exs:

def deps do
  [{:mnesiam, "~> 0.1.1"}]
end

Ensure mnesiam is started before your application.

Elixir Version >= 1.4 with libcluster

def application do
  [extra_applications: [:libcluster, :mnesiam]]
end

Elixir Version >= 1.4 without libcluster

def application do
  [extra_applications: [:mnesiam]]
end

Edit your app’s config.exs to add list of mnesia stores:

config :mnesiam,
  stores: [Mnesiam.Support.SampleStore, ...],
  table_load_timeout: 600_000 # milliseconds

Usage

Table creation

Create a table store and add it to your app’s config.exs. Note: All stores MUST implement its own init_store/0 to crete table and copy_store/0 to copy table:

defmodule Mnesiam.Support.SampleStore do
  @moduledoc """
  Sample store implementation
  """

  alias :mnesia, as: Mnesia

  @table :sample_store

  @doc """
  Mnesiam will call this method to init table
  """
  def init_store do
    Mnesia.create_table(@table,
      [ram_copies: [Node.self()], attributes: [:id, :topic_id, :event]])
    # Sample index
    Mnesia.add_table_index(@table, :topic_id)
    # Add table subscriptions to here
    # ...
  end

  @doc """
  Mnesiam will call this method to copy table
  """
  def copy_store do
    Mnesia.add_table_copy(@table, Node.self(), :ram_copies)
  end
end

Clustering

If you are using libcluster or another clustering library just ensure that clustering library starts earlier than mneasiam. That’s all, you do not need to do rest.

If you are not using libcluster or similar clustering library then:

• When a node joins to an erlang/elixir cluster, run Mnesiam.init_store() function on the new node; this will init and copy table contents from other online nodes.

Enjoy!

Warnings

Use at your own risk, no warranty!

Contributing

For any issues, bugs, documentation, enhancements:

1) Fork the project

2) Make your improvements and write your tests.

3) Make a pull request.

License

Apache License 2.0