tiagopog/cachex

A powerful caching library for Elixir with support for transactions, fallbacks and expirations

Cachex

Cachex is an extremely fast in-memory key/value store with support for many useful features:

• Time-based key expirations
• Maximum size protection
• Pre/post execution hooks
• Proactive/reactive cache warming
• Transactions and row locking
• Asynchronous write operations
• Distribution across app nodes
• Syncing to a local filesystem
• Idomatic cache streaming
• Batched write operations
• User command invocation
• Statistics gathering

All of these features are optional and are off by default so you can pick and choose those you wish to enable.

Table of Contents

• Installation
• Getting Started
  • Starting Your Cache
  • Main Interface
• Action Blocks
  • Execution Blocks
  • Transaction Blocks
• Cache Limits
  • Configuration
  • Policies
• Cache Warming
  • Reactive Warming
    • Overview
    • Courier
    • Expirations
    • Use Cases
  • Proactive Warming
    • Overview
    • Definition
    • Use Cases
• Custom Commands
  • Defining Commands
  • Invoking A Command
• Disk Interaction
• Distributed Caches
  • Overview
  • Local Actions
  • Disabled Actions
• Execution Hooks
  • Creating Hooks
  • Provisions
• Streaming Caches
  • Complex Streaming
• TTL Implementation
  • Janitor Processes
  • Lazy Expiration
• Migrations
  • Migrating To v3.x
  • Migrating To v2.x
• Benchmarks
• Contributions

Installation

As of v0.8.0, Cachex is available on Hex. You can install the package via:

1. Add cachex to your list of dependencies in mix.exs:

def deps do
  [{:cachex, "~> 3.2"}]
end

2. Ensure cachex is started before your application:

def application do
  [applications: [:cachex]]
end

Usage

The typical use of Cachex is to set up using a Supervisor, so that it can be handled automatically:

Supervisor.start_link(
  [Supervisor.Spec.worker(Cachex, [:my_cache, []])]
)

If your application was generated with a supervisor (by passing --sup to mix new) you will have a lib/my_app/application.ex file containing the application start callback that defines and starts your supervisor. You just need to edit the start/2 function to start Cachex as a supervisor on your application's supervisor:

import Supervisor.Spec, only: [worker: 2]

def start(_type, _args) do
  children = [
    ...,
    worker(Cachex, [:my_cache, []])
  ]

  opts = [strategy: :one_for_one, name: MyApp.Supervisor]
  Supervisor.start_link(children, opts)
end

Also, if you wish to start it manually (for example, in iex), you can just use Cachex.start_link/2:

Cachex.start_link(:my_cache, [])

For anything else, please see the documentation.

Benchmarks

There are some very trivial benchmarks available using Benchee in the benchmarks/ directory. You can run the benchmarks using the following command:

# default benchmarks, no modifiers
$ mix bench

# enable underlying table compression
$ CACHEX_BENCH_COMPRESS=true mix bench

# use a state instead of a cache name
$ CACHEX_BENCH_STATE=true mix bench

# use a lock write context for all writes
$ CACHEX_BENCH_TRANSACTIONS=true mix bench

Any combination of these environment variables is also possible, to allow you to test and benchmark your specific workflows.

Contributions

If you feel something can be improved, or have any questions about certain behaviours or pieces of implementation, please feel free to file an issue. Proposed changes should be taken to issues before any PRs to avoid wasting time on code which might not be merged upstream.

If you do make changes to the codebase, please make sure you test your changes thoroughly, and include any unit tests alongside new or changed behaviours. Cachex currently uses the excellent excoveralls to track code coverage.

$ mix test # --exclude=distributed to skip slower tests
$ mix credo
$ mix coveralls
$ mix coveralls.html && open cover/excoveralls.html