Nebulex 🌌

In-memory and distributed caching toolkit for Elixir.

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.

Nebulex cache abstraction shields developers from directly dealing with the underlying caching implementations, such as Redis, Memcached, or even other Elixir cache implementations like Cachex. Additionally, it provides totally out-of-box features such as cache usage patterns, declarative annotation-based caching, and distributed cache topologies, among others.

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:

Cache	Nebulex Adapter	Dependency
Generational Local Cache	Nebulex.Adapters.Local	Built-In
Partitioned	Nebulex.Adapters.Partitioned	Built-In
Replicated	Nebulex.Adapters.Replicated	Built-In
Multilevel	Nebulex.Adapters.Multilevel	Built-In
Nil (special adapter that disables the cache)	Nebulex.Adapters.Nil	Built-In
Cachex	Nebulex.Adapters.Cachex	nebulex_adapters_cachex
Redis	NebulexRedisAdapter	nebulex_redis_adapter
Distributed with Horde	Nebulex.Adapters.Horde	nebulex_adapters_horde
Multilevel with cluster broadcasting	NebulexLocalMultilevelAdapter	nebulex_local_multilevel_adapter

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

def deps do
  [
    {:nebulex, "~> 2.4"},
    {:shards, "~> 1.0"},     #=> When using :shards as backend
    {:decorator, "~> 1.4"},  #=> When using Caching Annotations
    {:telemetry, "~> 1.0"}   #=> When using the Telemetry events (Nebulex stats)
  ]
end

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

• For intensive workloads, you 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 to be dispatched when using Nebulex, you have to add :telemetry to the dependency list. See telemetry guide.

• If you want to use an external adapter (e.g: Cachex or Redis adapter), you have to add the adapter dependency too.

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

Quickstart example

Assuming you are using Ecto and you want to use declarative caching:

# In the config/config.exs file
config :my_app, MyApp.PartitionedCache,
  primary: [
    gc_interval: :timer.hours(12),
    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 :timer.hours(1)

  @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, user.id}, {User, user.username}],
              match: &match_update/1,
              opts: [ttl: @ttl]
            )
  def update_user(%User{} = user, attrs) do
    user
    |> User.changeset(attrs)
    |> Repo.update()
  end

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

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

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

See more Nebulex examples.

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.