Skip remote fetch jobs for unreachable instances

changelog.d/handle_object_fetch_failures.change

@@ -1,2 +1,3 @@
 Remote object fetch failures will prevent the object fetch job from retrying if the object has been deleted or the fetch was denied with a 403 due to instance block behavior with authorized_fetch enabled.
 Mark instances as unreachable when object fetch is denied due to instance block and authorized_fetch.
+Skip fetching objects from unreachable instances.

lib/pleroma/workers/remote_fetcher_worker.ex

@@ -3,12 +3,14 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 
 defmodule Pleroma.Workers.RemoteFetcherWorker do
+  alias Pleroma.Instances
   alias Pleroma.Object.Fetcher
 
   use Pleroma.Workers.WorkerHelper, queue: "remote_fetcher"
 
   @impl Oban.Worker
   def perform(%Job{args: %{"op" => "fetch_remote", "id" => id} = args}) do
+    if Instances.reachable?(id) do
       case Fetcher.fetch_object_from_id(id, depth: args["depth"]) do
         {:ok, _object} ->
           :ok
@@ -22,5 +24,8 @@ defmodule Pleroma.Workers.RemoteFetcherWorker do
         _ ->
           :error
       end
+    else
+      {:cancel, "Unreachable instance"}
+    end
   end
 end