Nebulex Local

A generational local cache adapter for Nebulex.

About

nebulex_local is an in-memory cache adapter for Nebulex, inspired by epocxy. It stores entries in ETS and uses two generations, newer and older, to manage eviction. Fetching an entry from the older generation moves it into the newer one. When the cache creates a new generation, it retires the oldest.

See the module documentation for details on expiration, eviction, concurrency, and configuration.

Installation

Add :nebulex_local to your list of dependencies in mix.exs:

def deps do
  [
    {:nebulex_local, "~> 3.1"},
    {:telemetry, "~> 0.4 or ~> 1.0"}, # For observability/telemetry support
    {:decorator, "~> 1.4"},           # For declarative caching
    {:shards, "~> 1.1"},              # For high concurrency workloads with partitioning
    {:ex2ms, "~> 1.7"}                # For match specification query helpers
  ]
end

The following dependencies are optional. Add the ones your application uses:

:telemetry - To emit and consume Telemetry events for cache operations (recommended).
:decorator - To use the declarative caching decorators (recommended).
:shards - To use backend: :shards, which partitions the cache across several ETS tables for intensive workloads.
:ex2ms - To build match spec queries with Nebulex.Adapters.Local.QueryHelper.

Usage

Define a cache module:

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

Configure the cache in your application environment, usually in config/config.exs:

config :my_app, MyApp.LocalCache,
  gc_interval: :timer.hours(12),
  max_size: 1_000_000,
  allocated_memory: 2_000_000_000,
  gc_memory_check_interval: :timer.seconds(10)

Add the cache to your application's supervision tree, usually in lib/my_app/application.ex:

def start(_type, _args) do
  children = [
    MyApp.LocalCache
  ]

  opts = [strategy: :one_for_one, name: MyApp.Supervisor]

  Supervisor.start_link(children, opts)
end

See the online documentation for more information.

Testing

The test suite uses support modules and shared tests from the Nebulex repository, which are not included in the Hex package. Fetch the dependencies, clone Nebulex with mix nbx.setup, and run the tests with NEBULEX_PATH pointing to that checkout:

mix deps.get
mix nbx.setup
NEBULEX_PATH=nebulex mix test

Running tests with coverage:

NEBULEX_PATH=nebulex mix coveralls.html

You will find the coverage report within cover/excoveralls.html.

Benchmarks

The benchmarks directory contains benchmarks for both backends, written with Benchee. To run one:

$ 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.

For example, to run the benchmark for the :shards backend:

$ MIX_ENV=test mix run benchmarks/local_with_shards_bench.exs

You can also run performance tests with :basho_bench. See the nebulex_bench example.

Contributing

Use the issue tracker for bug reports and feature requests. Contributions are welcome through pull requests.

Include tests for new or changed behavior, and leave CHANGELOG.md unchanged. Before submitting a pull request, run NEBULEX_PATH=nebulex mix precommit and fix any failures.

Copyright and License

nebulex_local source code is licensed under the MIT License.