Plug.PageCache

Plug for full page response caching.

Warning

This is not the plug you are looking for!

Well, perhaps at least. There is no "one size fits all" caching solution.

This plug should better be seen as "food for thought" or an easy way to just plug some cache into your application and see what happens.

Question this library might answer:

"Would my site be any faster if the complete page would be served from memory?"

Setup

Add the plug as a dependency to your mix.exs file:

defp deps do
  [ { :plug_pagecache, "~> 0.2" } ]
end

You should also update your applications to include all necessary projects:

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

Usage

Configuration

Define your caches in your config.exs:

use Mix.Config

config :plug_pagecache,
  :caches,
    my_agent_cache: [
      adapter:     Plug.PageCache.Adapter.Agent,
      auto_expire: 3600
    ],
    my_ets_cache: [
      adapter:     Plug.PageCache.Adapter.ETS,
      auto_expire: 3600,
      table:       :my_ets_table
    ]

Every cache is configured using an internal name as the key and a Keyword.t for details. The key :adapter is always necessary, other configuration values depend on the used adapter.

Plugging

Add the cache you have configured to your plug pipeline:

defmodule AppRouter do
  use Plug.Router

  plug Plug.PageCache, cache: :my_configured_cache

  # ...

  plug :match
  plug :dispatch

  # ...
end

Any not nil response body will be cached after dispatching using the served path as the key. If there is a cached response available it will be sent with the response status 200 (OK) to the client.

Invalidation

As there is no automatic expiration/invalidation these things have to be done manually:

cache   = Config.cache_id(:my_configured_cache)
request = { :remove, "/path/to/be/invalidated" }

:ok = GenServer.call(cache, request)

Cleaning all entries is also possible:

cache   = Config.cache_id(:my_configured_cache)
request = :clean

:ok = GenServer.call(cache, request)

Available Adapters

Plug.PageCache.Adapter.Agent

Uses a plain GenServer to serve responses directly from memory (== state).

Requires no additional configuration.

Optionally takes an :auto_expire value as entry lifetime in seconds.

Plug.PageCache.Adapter.ETS

Uses an ets table to serve responses.

Responses are stored in a :named_table you have to configure using the :table key.