Nebulex.Adapters.DiskLFU

Persistent disk-based cache adapter with LFU eviction for Nebulex.

About

Nebulex.Adapters.DiskLFU is a persistent LFU (Least Frequently Used) cache adapter for Nebulex, designed to provide an SSD-backed cache with disk persistence, TTL support, and LFU-based eviction. This adapter is ideal for workloads that require:

• High-capacity caching without exhausting memory.
• File-based persistence with cache recovery after restarts.
• Concurrency-safe operations for both reads and writes.
• Customizable eviction strategies.

Features

• LFU Eviction - Least Frequently Used eviction when disk capacity is exceeded.
• TTL Support - Per-entry time-to-live with lazy and proactive cleanup.
• Proactive Eviction - Automatic periodic cleanup of expired entries via :eviction_timeout.
• Manual Cleanup - Direct API for explicit expired entry removal with delete_all(query: :expired).
• Concurrent Access - Safe read/write operations with atomic guarantees per key.
• Persistent - Survives application restarts with fast recovery from disk.

For comprehensive information on architecture, features, and configuration, see the Full Documentation and Architecture Guide.

Installation

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

def deps do
  [
    {:nebulex_disk_lfu, "~> 3.1"},
    {:telemetry, "~> 0.4 or ~> 1.0"}  # For observability/telemetry support
  ]
end

The :telemetry dependency is optional but highly recommended for observability and monitoring cache operations.

See the online documentation for more information.

Usage

Define your cache module:

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

Configure your cache in config/config.exs:

config :my_app, MyApp.Cache,
  root_path: "/var/cache",
  max_bytes: 10_000_000,               # 10MB capacity
  eviction_timeout: :timer.minutes(5)  # Clean expired entries every 5 minutes

Add the cache to your application supervision tree:

def start(_type, _args) do
  children = [
    {MyApp.Cache, []},
    # ... other children
  ]

  Supervisor.start_link(children, strategy: :one_for_one)
end

Then use it in your application:

# Write a value with TTL
MyApp.Cache.put(:key, "value", ttl: :timer.hours(1))

# Read a value
MyApp.Cache.get(:key)

# Delete expired entries manually
MyApp.Cache.delete_all(query: :expired)

For detailed API documentation, configuration options, and more examples, see the Adapter Documentation.

Benchmarks

Benchmarks were added using benchee, and they are located within the directory benchmarks.

To run the benchmarks:

mix run benchmarks/benchmark.exs

Documentation

• Full Adapter Documentation - Complete API reference and configuration options.
• Architecture Guide - Design, eviction strategy, and concurrency model.
• Nebulex Documentation - General cache framework documentation.

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 mix precommit and fix any failures.

Sponsor

• StanfordTax

Copyright and License

Copyright (c) 2025, Carlos Bolaños.

Nebulex.Adapters.DiskLFU source code is licensed under the MIT License.