Set instance reachable on fetch

lib/pleroma/object/fetcher.ex

@@ -4,6 +4,7 @@
 
 defmodule Pleroma.Object.Fetcher do
   alias Pleroma.HTTP
+  alias Pleroma.Instances
   alias Pleroma.Maps
   alias Pleroma.Object
   alias Pleroma.Object.Containment
@@ -234,6 +235,10 @@ def fetch_and_contain_remote_object_from_id(id) when is_binary(id) do
          {:ok, body} <- get_object(id),
          {:ok, data} <- safe_json_decode(body),
          :ok <- Containment.contain_origin_from_id(id, data) do
+      unless Instances.reachable?(id) do
+        Instances.set_reachable(id)
+      end
+
       {:ok, data}
     else
       {:scheme, _} ->

test/pleroma/object/fetcher_test.exs

@@ -6,6 +6,7 @@ defmodule Pleroma.Object.FetcherTest do
   use Pleroma.DataCase
 
   alias Pleroma.Activity
+  alias Pleroma.Instances
   alias Pleroma.Object
   alias Pleroma.Object.Fetcher
 
@@ -159,6 +160,17 @@ test "it does not fetch a spoofed object uploaded on an instance as an attachmen
                  "https://patch.cx/media/03ca3c8b4ac3ddd08bf0f84be7885f2f88de0f709112131a22d83650819e36c2.json"
                )
     end
+
+    test "it resets instance reachability on successful fetch" do
+      id = "http://mastodon.example.org/@admin/99541947525187367"
+      Instances.set_consistently_unreachable(id)
+      refute Instances.reachable?(id)
+
+      {:ok, object} =
+        Fetcher.fetch_object_from_id("http://mastodon.example.org/@admin/99541947525187367")
+
+      assert Instances.reachable?(id)
+    end
   end
 
   describe "implementation quirks" do