# Mnesiac
[](https://travis-ci.org/beardedeagle/mnesiac) [](https://codecov.io/gh/beardedeagle/mnesiac) [](https://hex.pm/packages/mnesiac) [](https://hex.pm/packages/mnesiac)
mnesia autoclustering made easy!
Docs can be found at [https://hexdocs.pm/mnesiac](https://hexdocs.pm/mnesiac).
## Installation
Simply add `mnesiac` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[
{:mnesiac, "~> 0.2.0"}
]
end
```
Edit your app's config.exs to add the list of mnesia stores:
```elixir
config :mnesiac,
stores: [Mnesiac.ExampleStore, ...],
schema_type: :disc_copies, # defaults to :ram_copies
table_load_timeout: 600_000 # milliseconds, default is 600_000
```
And then add `mnesiac` to your supervision tree:
With `libcluster`:
```elixir
...
topology = Application.get_env(:libcluster, :topologies)
hosts = topology[:myapp][:config][:hosts]
children = [
{Cluster.Supervisor, [topology, [name: MyApp.ClusterSupervisor]]},
{Mnesiac.Supervisor, [hosts, [name: MyApp.MnesiacSupervisor]]},
...
]
...
```
Without `libcluster`:
```elixir
...
children = [
{
Mnesiac.Supervisor,
[
[:"test01@127.0.0.1", :"test02@127.0.0.1"],
[name: MyApp.MnesiacSupervisor]
]
},
...
]
...
```
## 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 create a table and `copy_store/0` to copy a table:
```elixir
defmodule MyApp.ExampleStore do
@moduledoc """
Example store implementation
"""
require Record
Record.defrecord(
:example,
ExampleStore,
id: nil,
topic_id: nil,
event: nil
)
@type example ::
record(
:example,
id: String.t(),
topic_id: String.t(),
event: String.t()
)
@doc """
Mnesiac will call this method to initialize the table
"""
def init_store do
:mnesia.create_table(
ExampleStore,
attributes: example() |> example() |> Keyword.keys(),
index: [:topic_id],
disc_copies: [Node.self()]
)
end
@doc """
Mnesiac will call this method to copy the table
"""
def copy_store do
:mnesia.add_table_copy(ExampleStore, Node.self(), :disc_copies)
end
...
end
```
### Clustering
If you are using `libcluster` or another clustering library just ensure that clustering library starts earlier than `mneasiac`. 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 the `Mnesiac.init_mnesia()` function on the *new node*. This will initialize and copy table contents from the other online nodes.
## Development
Run the following:
```shell
git clone https://github.com/beardedeagle/mnesiac.git
git checkout -b MyFeature
mix deps.get --force
mix deps.compile --force
mix compile --force
mix check
```
## Testing
Before you run any tests, ensure that you have cleaned up mnesia:
```shell
mix purge.db
```
Test results and coverage reports are generated by running the following:
```shell
mix test
```
## Notice
This library was built standing on the shoulders of giants. A big thanks goes out to Mustafa Turan. The original library this was forked from can be found here: <https://github.com/mustafaturan/mnesiam>.
Enjoy!
