Mcc (Mnesia Cluster Cache)

mcc is Mnesia Cluster Cache, which support expiration and cluster.

usage

There are some steps to use mcc:

define table
define model
start expiration process

define table

Mcc support expiration and each table need one assistant table to store expiration information.

  use Mcc.Model.Table,
    table_opts: [
      type: :set,
      ram_copies: [node()],
      storage_properties: [
        ets: [:compressed, read_concurrency: true]
      ]
    ],
    expiration_opts: [
      expiration_table: AccountExp,
      main_table: MccTest.Support.Table.Account,
      size_limit: 100,
      # 300M
      memory_limit: 300
    ]

  defstruct([:id, :user_profile], true)

Like above table definition, the table_opts is from mnesia create table. And expiration_opts has several option:

expiration_table which table to store expiration information
main_table current table
size_limit the table size limit
memory_limit the memory usage limit, unit is mega byte

After define the table, need define the fields for the table, user can use defstruct/1,2 to define the table's fields. Multi-fields use [] to organize, and fields should use atom. The second parameter for defstruct is represent if use cache expiration mechanism.

For the assistant table, the definition will be like:

defmodule MccTest.Support.Table.Account.Exp do
  @moduledoc """
  Table for expiration Account table.
  """

  use Mcc.Model.Table,
    table_opts: [
      type: :ordered_set,
      ram_copies: [node()],
      storage_properties: [
        ets: [:compressed, read_concurrency: true]
      ]
    ]

  defstruct [:key, :value]

  def put(key, value) do
    put(%__MODULE__{key: key, value: value})
  end
end

define model

After define table, user need to define model, it's not difficult:

defmodule MccTest.Support.Cache do
  @moduledoc """
  Definition for cache test.
  """

  use Mcc.Model

  import_table(MccTest.Support.Table.Account.Exp)
  import_table(MccTest.Support.Table.Account)
end

define model is import the tables which defined before.

start expiration process

mcc use one long-lived process to scan the mnesia table for expiration. User(application) need to start the process explicitly:

MccTest.Support.Cache.start_expiration_process()

Generally speaking, it will be put into application start.

[One complete example could be found in the test cases]

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