diff --git a/CHANGELOG.md b/CHANGELOG.md
index a65988991..a6ec8674d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,10 @@ All notable changes to this project will be documented in this file.
The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
+## [Unreleased]
+### Added
+- MRF: Support for priming the mediaproxy cache (`Pleroma.Web.ActivityPub.MRF.MediaProxyWarmingPolicy`)
+
## [1.0.0] - 2019-06-29
### Security
- Mastodon API: Fix display names not being sanitized
diff --git a/docs/config.md b/docs/config.md
index 7a53364ef..7d5be3980 100644
--- a/docs/config.md
+++ b/docs/config.md
@@ -98,6 +98,7 @@ config :pleroma, Pleroma.Emails.Mailer,
* `Pleroma.Web.ActivityPub.MRF.RejectNonPublic`: Drops posts with non-public visibility settings (See ``:mrf_rejectnonpublic`` section)
* `Pleroma.Web.ActivityPub.MRF.EnsureRePrepended`: Rewrites posts to ensure that replies to posts with subjects do not have an identical subject and instead begin with re:.
* `Pleroma.Web.ActivityPub.MRF.AntiLinkSpamPolicy`: Rejects posts from likely spambots by rejecting posts from new users that contain links.
+ * `Pleroma.Web.ActivityPub.MRF.MediaProxyWarmingPolicy`: Crawls attachments using their MediaProxy URLs so that the MediaProxy cache is primed.
* `public`: Makes the client API in authentificated mode-only except for user-profiles. Useful for disabling the Local Timeline and The Whole Known Network.
* `quarantined_instances`: List of ActivityPub instances where private(DMs, followers-only) activities will not be send.
* `managed_config`: Whenether the config for pleroma-fe is configured in this config or in ``static/config.json``
diff --git a/lib/pleroma/web/activity_pub/mrf/mediaproxy_warming_policy.ex b/lib/pleroma/web/activity_pub/mrf/mediaproxy_warming_policy.ex
new file mode 100644
index 000000000..01d21a299
--- /dev/null
+++ b/lib/pleroma/web/activity_pub/mrf/mediaproxy_warming_policy.ex
@@ -0,0 +1,56 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2019 Pleroma Authors
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.ActivityPub.MRF.MediaProxyWarmingPolicy do
+ @moduledoc "Preloads any attachments in the MediaProxy cache by prefetching them"
+ @behaviour Pleroma.Web.ActivityPub.MRF
+
+ alias Pleroma.HTTP
+ alias Pleroma.Web.MediaProxy
+
+ require Logger
+
+ @hackney_options [
+ pool: :media,
+ recv_timeout: 10_000
+ ]
+
+ def perform(:prefetch, url) do
+ Logger.info("Prefetching #{inspect(url)}")
+
+ url
+ |> MediaProxy.url()
+ |> HTTP.get([], adapter: @hackney_options)
+ end
+
+ def perform(:preload, %{"object" => %{"attachment" => attachments}} = _message) do
+ Enum.each(attachments, fn
+ %{"url" => url} when is_list(url) ->
+ url
+ |> Enum.each(fn
+ %{"href" => href} ->
+ PleromaJobQueue.enqueue(:background, __MODULE__, [:prefetch, href])
+
+ x ->
+ Logger.debug("Unhandled attachment URL object #{inspect(x)}")
+ end)
+
+ x ->
+ Logger.debug("Unhandled attachment #{inspect(x)}")
+ end)
+ end
+
+ @impl true
+ def filter(
+ %{"type" => "Create", "object" => %{"attachment" => attachments} = _object} = message
+ )
+ when is_list(attachments) and length(attachments) > 0 do
+ PleromaJobQueue.enqueue(:background, __MODULE__, [:preload, message])
+
+ {:ok, message}
+ end
+
+ @impl true
+ def filter(message), do: {:ok, message}
+end
diff --git a/test/web/activity_pub/mrf/mediaproxy_warming_policy_test.exs b/test/web/activity_pub/mrf/mediaproxy_warming_policy_test.exs
new file mode 100644
index 000000000..372e789be
--- /dev/null
+++ b/test/web/activity_pub/mrf/mediaproxy_warming_policy_test.exs
@@ -0,0 +1,45 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2019 Pleroma Authors
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.ActivityPub.MRF.MediaProxyWarmingPolicyTest do
+ use Pleroma.DataCase
+
+ alias Pleroma.HTTP
+ alias Pleroma.Web.ActivityPub.MRF.MediaProxyWarmingPolicy
+
+ import Mock
+
+ @message %{
+ "type" => "Create",
+ "object" => %{
+ "type" => "Note",
+ "content" => "content",
+ "attachment" => [
+ %{"url" => [%{"href" => "http://example.com/image.jpg"}]}
+ ]
+ }
+ }
+
+ test "it prefetches media proxy URIs" do
+ with_mock HTTP, get: fn _, _, _ -> {:ok, []} end do
+ MediaProxyWarmingPolicy.filter(@message)
+ assert called(HTTP.get(:_, :_, :_))
+ end
+ end
+
+ test "it does nothing when no attachments are present" do
+ object =
+ @message["object"]
+ |> Map.delete("attachment")
+
+ message =
+ @message
+ |> Map.put("object", object)
+
+ with_mock HTTP, get: fn _, _, _ -> {:ok, []} end do
+ MediaProxyWarmingPolicy.filter(message)
+ refute called(HTTP.get(:_, :_, :_))
+ end
+ end
+end