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   1 # Pleroma: A lightweight social networking server
   2 # Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
   3 # SPDX-License-Identifier: AGPL-3.0-only
   4
   5 defmodule Pleroma.Web.Plugs.Cache do
   6   @moduledoc """
   7   Caches successful GET responses.
   8
   9   To enable the cache add the plug to a router pipeline or controller:
  10
  11       plug(Pleroma.Web.Plugs.Cache)
  12
  13   ## Configuration
  14
  15   To configure the plug you need to pass settings as the second argument to the `plug/2` macro:
  16
  17       plug(Pleroma.Web.Plugs.Cache, [ttl: nil, query_params: true])
  18
  19   Available options:
  20
  21   - `ttl`:  An expiration time (time-to-live). This value should be in milliseconds or `nil` to disable expiration. Defaults to `nil`.
  22   - `query_params`: Take URL query string into account (`true`), ignore it (`false`) or limit to specific params only (list). Defaults to `true`.
  23   - `tracking_fun`: A function that is called on successfull responses, no matter if the request is cached or not. It should accept a conn as the first argument and the value assigned to `tracking_fun_data` as the second.
  24
  25   Additionally, you can overwrite the TTL inside a controller action by assigning `cache_ttl` to the connection struct:
  26
  27       def index(conn, _params) do
  28         ttl = 60_000 # one minute
  29
  30         conn
  31         |> assign(:cache_ttl, ttl)
  32         |> render("index.html")
  33       end
  34
  35   """
  36
  37   import Phoenix.Controller, only: [current_path: 1, json: 2]
  38   import Plug.Conn
  39
  40   @behaviour Plug
  41
  42   @defaults %{ttl: nil, query_params: true}
  43
  44   @impl true
  45   def init([]), do: @defaults
  46
  47   def init(opts) do
  48     opts = Map.new(opts)
  49     Map.merge(@defaults, opts)
  50   end
  51
  52   @impl true
  53   def call(%{method: "GET"} = conn, opts) do
  54     key = cache_key(conn, opts)
  55
  56     case Cachex.get(:web_resp_cache, key) do
  57       {:ok, nil} ->
  58         cache_resp(conn, opts)
  59
  60       {:ok, {content_type, body, tracking_fun_data}} ->
  61         conn = opts.tracking_fun.(conn, tracking_fun_data)
  62
  63         send_cached(conn, {content_type, body})
  64
  65       {:ok, record} ->
  66         send_cached(conn, record)
  67
  68       {atom, message} when atom in [:ignore, :error] ->
  69         render_error(conn, message)
  70     end
  71   end
  72
  73   def call(conn, _), do: conn
  74
  75   # full path including query params
  76   defp cache_key(conn, %{query_params: true}), do: current_path(conn)
  77
  78   # request path without query params
  79   defp cache_key(conn, %{query_params: false}), do: conn.request_path
  80
  81   # request path with specific query params
  82   defp cache_key(conn, %{query_params: query_params}) when is_list(query_params) do
  83     query_string =
  84       conn.params
  85       |> Map.take(query_params)
  86       |> URI.encode_query()
  87
  88     conn.request_path <> "?" <> query_string
  89   end
  90
  91   defp cache_resp(conn, opts) do
  92     register_before_send(conn, fn
  93       %{status: 200, resp_body: body} = conn ->
  94         ttl = Map.get(conn.assigns, :cache_ttl, opts.ttl)
  95         key = cache_key(conn, opts)
  96         content_type = content_type(conn)
  97
  98         conn =
  99           unless opts[:tracking_fun] do
 100             Cachex.put(:web_resp_cache, key, {content_type, body}, ttl: ttl)
 101             conn
 102           else
 103             tracking_fun_data = Map.get(conn.assigns, :tracking_fun_data, nil)
 104             Cachex.put(:web_resp_cache, key, {content_type, body, tracking_fun_data}, ttl: ttl)
 105
 106             opts.tracking_fun.(conn, tracking_fun_data)
 107           end
 108
 109         put_resp_header(conn, "x-cache", "MISS from Pleroma")
 110
 111       conn ->
 112         conn
 113     end)
 114   end
 115
 116   defp content_type(conn) do
 117     conn
 118     |> Plug.Conn.get_resp_header("content-type")
 119     |> hd()
 120   end
 121
 122   defp send_cached(conn, {content_type, body}) do
 123     conn
 124     |> put_resp_content_type(content_type, nil)
 125     |> put_resp_header("x-cache", "HIT from Pleroma")
 126     |> send_resp(:ok, body)
 127     |> halt()
 128   end
 129
 130   defp render_error(conn, message) do
 131     conn
 132     |> put_status(:internal_server_error)
 133     |> json(%{error: message})
 134     |> halt()
 135   end
 136 end