Cache follow state

lib/pleroma/user.ex

@@ -132,6 +132,28 @@ defmodule Pleroma.User do
     |> Map.put(:follower_count, follower_count)
   end
 
+  def follow_state(%User{} = user, %User{} = target) do
+    follow_activity = Utils.fetch_latest_follow(user, target)
+
+    if follow_activity,
+      do: follow_activity.data["state"],
+      # Ideally this would be nil, but then Cachex does not commit the value
+      else: false
+  end
+
+  def get_cached_follow_state(user, target) do
+    key = "follow_state:#{user.ap_id}|#{target.ap_id}"
+    Cachex.fetch!(:user_cache, key, fn _ -> {:commit, follow_state(user, target)} end)
+  end
+
+  def set_follow_state_cache(user_ap_id, target_ap_id, state) do
+    Cachex.put(
+      :user_cache,
+      "follow_state:#{user_ap_id}|#{target_ap_id}",
+      state
+    )
+  end
+
   def set_info_cache(user, args) do
     Cachex.put(:user_cache, "user_info:#{user.id}", user_info(user, args))
   end

lib/pleroma/web/activity_pub/activity_pub.ex

@@ -388,7 +388,8 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
   def follow(follower, followed, activity_id \\ nil, local \\ true) do
     with data <- make_follow_data(follower, followed, activity_id),
          {:ok, activity} <- insert(data, local),
-         :ok <- maybe_federate(activity) do
+         :ok <- maybe_federate(activity),
+         _ <- User.set_follow_state_cache(follower.ap_id, followed.ap_id, activity.data["state"]) do
       {:ok, activity}
     end
   end

lib/pleroma/web/activity_pub/utils.ex

@@ -374,6 +374,7 @@ defmodule Pleroma.Web.ActivityPub.Utils do
         [state, actor, object]
       )
 
+      User.set_follow_state_cache(actor, object, state)
       activity = Activity.get_by_id(activity.id)
       {:ok, activity}
     rescue
@@ -382,12 +383,16 @@ defmodule Pleroma.Web.ActivityPub.Utils do
     end
   end
 
-  def update_follow_state(%Activity{} = activity, state) do
+  def update_follow_state(
+        %Activity{data: %{"actor" => actor, "object" => object}} = activity,
+        state
+      ) do
     with new_data <-
            activity.data
            |> Map.put("state", state),
          changeset <- Changeset.change(activity, data: new_data),
-         {:ok, activity} <- Repo.update(changeset) do
+         {:ok, activity} <- Repo.update(changeset),
+         _ <- User.set_follow_state_cache(actor, object, state) do
       {:ok, activity}
     end
   end

lib/pleroma/web/mastodon_api/views/account_view.ex

@@ -37,11 +37,11 @@ defmodule Pleroma.Web.MastodonAPI.AccountView do
   end
 
   def render("relationship.json", %{user: %User{} = user, target: %User{} = target}) do
-    follow_activity = Pleroma.Web.ActivityPub.Utils.fetch_latest_follow(user, target)
+    follow_state = User.get_cached_follow_state(user, target)
 
     requested =
-      if follow_activity && !User.following?(target, user) do
-        follow_activity.data["state"] == "pending"
+      if follow_state && !User.following?(user, target) do
+        follow_state == "pending"
       else
         false
       end