Nebulex 🌌

In-Process and Distributed Cache Toolkit for Elixir.

Easily craft and deploy distributed cache topologies and cache usage patterns.

Nebulex provides support for transparently adding caching into an existing Elixir application. Similar to Ecto, the caching abstraction allows consistent use of various caching solutions with minimal impact on the code. Furthermore, it enables the implementation of different cache usage patterns, distributed cache topologies, and more.

Supposing we are using Ecto and we want to apply caching declaratively on some functions:

# In the config/config.exs file
config :my_app, MyApp.PartitionedCache,
  primary: [
    gc_interval: :timer.seconds(3600),
    backend: :shards,
    partitions: 2
  ]

# Defining a Cache with a partitioned topology
defmodule MyApp.PartitionedCache do
  use Nebulex.Cache,
    otp_app: :my_app,
    adapter: Nebulex.Adapters.Partitioned,
    primary_storage_adapter: Nebulex.Adapters.Local
end

# Some Ecto schema
defmodule MyApp.Accounts.User do
  use Ecto.Schema

  schema "users" do
    field(:username, :string)
    field(:password, :string)
    field(:role, :string)
  end

  def changeset(user, attrs) do
    user
    |> cast(attrs, [:username, :password, :role])
    |> validate_required([:username, :password, :role])
  end
end

# The Accounts context
defmodule MyApp.Accounts do
  use Nebulex.Caching

  alias MyApp.Accounts.User
  alias MyApp.PartitionedCache, as: Cache
  alias MyApp.Repo

  @ttl Nebulex.Time.expiry_time(1, :hour)

  @decorate cacheable(cache: Cache, key: {User, id}, opts: [ttl: @ttl])
  def get_user!(id) do
    Repo.get!(User, id)
  end

  @decorate cacheable(cache: Cache, key: {User, username}, opts: [ttl: @ttl])
  def get_user_by_username(username) do
    Repo.get_by(User, [username: username])
  end

  @decorate cache_put(
              cache: Cache,
              keys: [{User, usr.id}, {User, usr.username}],
              match: &match_update/1
            )
  def update_user(%User{} = usr, attrs) do
    usr
    |> User.changeset(attrs)
    |> Repo.update()
  end

  defp match_update({:ok, usr}), do: {true, usr}
  defp match_update({:error, _}), do: false

  @decorate cache_evict(cache: Cache, keys: [{User, usr.id}, {User, usr.username}])
  def delete_user(%User{} = usr) do
    Repo.delete(usr)
  end

  def create_user(attrs \\ %{}) do
    %User{}
    |> User.changeset(attrs)
    |> Repo.insert()
  end
end

Nebulex is commonly used to interact with different cache implementations and/or stores (such as Redis, Memcached, or other implementations of cache in Elixir), being completely agnostic from them, avoiding the vendor lock-in.

See the getting started guide and the online documentation for more information.

Usage

You need to add nebulex as a dependency to your mix.exs file. However, in the case you want to use an external (a non built-in adapter) cache adapter, you also have to add the proper dependency to your mix.exs file.

The supported caches and their adapters are:

For example, if you want to use a built-in cache, add to your mix.exs file:

def deps do
  [
    {:nebulex, "2.0.0-rc.1"},
    {:shards, "~> 1.0"},     #=> When using :shards as backend
    {:decorator, "~> 1.3"},  #=> When using Caching Annotations
    {:telemetry, "~> 0.4"}   #=> When using the Telemetry events (Nebulex stats)
  ]
end

In order to give more flexibility and loading only needed dependencies, Nebulex makes all its dependencies as optional. For example:

• For intensive workloads, we may want to use :shards as the backend for the local adapter and having partitioned tables. In such a case, you have to add :shards to the dependency list.

• For enabling the usage of declarative annotation-based caching via decorators, you have to add :decorator to the dependency list.

• For enabling Telemetry events dispatched when using Nebulex stats you have to add :telemetry to the dependency list. See telemetry guide.

• Also, all the external adapters have to be added as a dependency as well.

Then run mix deps.get in your shell to fetch the dependencies. If you want to use another cache adapter, just choose the proper dependency from the table above.

Finally, in the cache definition, you will need to specify the adapter: respective to the chosen dependency. For the local built-in cache it is:

defmodule MyApp.Cache do
  use Nebulex.Cache,
    otp_app: :my_app,
    adapter: Nebulex.Adapters.Local
end

Important links

• Getting Started
• Documentation
• Cache Usage Patterns
• Instrumenting the Cache with Telemetry
• Migrating to v2.x
• Examples

Testing

Testing by default spawns nodes internally for distributed tests. To run tests that do not require clustering, exclude the clustered tag:

$ mix test --exclude clustered

If you have issues running the clustered tests try running:

$ epmd -daemon

before running the tests.

Benchmarks

Nebulex provides a set of basic benchmark tests using the library benchee, and they are located within the directory benchmarks.

To run a benchmark test you have to run:

$ MIX_ENV=test mix run benchmarks/{BENCH_TEST_FILE}

Where BENCH_TEST_FILE can be any of:

• local_with_ets_bench.exs: benchmark for the local adapter using :ets backend.
• local_with_shards_bench.exs: benchmark for the local adapter using :shards backend.
• partitioned_bench.exs: benchmark for the partitioned adapter.

For example, for running the benchmark for the local adapter using :shards backend:

$ MIX_ENV=test mix run benchmarks/local_with_shards_bench.exs

Additionally, you can also run performance tests using :basho_bench. See nebulex_bench example for more information.

Contributing

Contributions to Nebulex are very welcome and appreciated!

Use the issue tracker for bug reports or feature requests. Open a pull request when you are ready to contribute.

When submitting a pull request you should not update the CHANGELOG.md, and also make sure you test your changes thoroughly, include unit tests alongside new or changed code.

Before to submit a PR it is highly recommended to run mix check and ensure all checks run successfully.

Copyright and License

Copyright (c) 2017, Carlos Bolaños.

Nebulex source code is licensed under the MIT License.