3 files changed, 49 insertions, 7 deletions
diff --git a/lib/pleroma/plugs/rate_limiter/limiter_supervisor.ex b/lib/pleroma/plugs/rate_limiter/limiter_supervisor.ex
index 187582ede..884268d96 100644
--- a/lib/pleroma/plugs/rate_limiter/limiter_supervisor.ex
+++ b/lib/pleroma/plugs/rate_limiter/limiter_supervisor.ex
@@ -7,8 +7,8 @@ defmodule Pleroma.Plugs.RateLimiter.LimiterSupervisor do
     DynamicSupervisor.start_link(__MODULE__, init_arg, name: __MODULE__)
   end
 
-  def add_limiter(limiter_name, expiration) do
-    {:ok, _pid} =
+  def add_or_return_limiter(limiter_name, expiration) do
+    result =
       DynamicSupervisor.start_child(
         __MODULE__,
         %{
@@ -28,6 +28,12 @@ defmodule Pleroma.Plugs.RateLimiter.LimiterSupervisor do
              ]}
         }
       )
+
+    case result do
+      {:ok, _pid} = result -> result
+      {:error, {:already_started, pid}} -> {:ok, pid}
+      _ -> result
+    end
   end
 
   @impl true
diff --git a/lib/pleroma/plugs/rate_limiter/rate_limiter.ex b/lib/pleroma/plugs/rate_limiter/rate_limiter.ex
index 9c362a392..b9cbe9716 100644
--- a/lib/pleroma/plugs/rate_limiter/rate_limiter.ex
+++ b/lib/pleroma/plugs/rate_limiter/rate_limiter.ex
@@ -171,7 +171,7 @@ defmodule Pleroma.Plugs.RateLimiter do
         {:error, value}
 
       {:error, :no_cache} ->
-        initialize_buckets(action_settings)
+        initialize_buckets!(action_settings)
         check_rate(action_settings)
     end
   end
@@ -250,11 +250,16 @@ defmodule Pleroma.Plugs.RateLimiter do
     |> String.replace_leading(":", "")
   end
 
-  defp initialize_buckets(%{name: _name, limits: nil}), do: :ok
+  defp initialize_buckets!(%{name: _name, limits: nil}), do: :ok
 
-  defp initialize_buckets(%{name: name, limits: limits}) do
-    LimiterSupervisor.add_limiter(anon_bucket_name(name), get_scale(:anon, limits))
-    LimiterSupervisor.add_limiter(user_bucket_name(name), get_scale(:user, limits))
+  defp initialize_buckets!(%{name: name, limits: limits}) do
+    {:ok, _pid} =
+      LimiterSupervisor.add_or_return_limiter(anon_bucket_name(name), get_scale(:anon, limits))
+
+    {:ok, _pid} =
+      LimiterSupervisor.add_or_return_limiter(user_bucket_name(name), get_scale(:user, limits))
+
+    :ok
   end
 
   defp attach_identity(base, %{mode: :user, conn_info: conn_info}),
diff --git a/test/plugs/rate_limiter_test.exs b/test/plugs/rate_limiter_test.exs
index 104d67611..8cdc8d1a2 100644
--- a/test/plugs/rate_limiter_test.exs
+++ b/test/plugs/rate_limiter_test.exs
@@ -242,4 +242,35 @@ defmodule Pleroma.Plugs.RateLimiterTest do
       refute conn_2.halted
     end
   end
+
+  test "doesn't crash due to a race condition when multiple requests are made at the same time and the bucket is not yet initialized" do
+    limiter_name = :test_race_condition
+    Pleroma.Config.put([:rate_limit, limiter_name], {1000, 5})
+    Pleroma.Config.put([Pleroma.Web.Endpoint, :http, :ip], {8, 8, 8, 8})
+
+    opts = RateLimiter.init(name: limiter_name)
+
+    conn = conn(:get, "/")
+    conn_2 = conn(:get, "/")
+
+    %Task{pid: pid1} =
+      task1 =
+      Task.async(fn ->
+        receive do
+          :process2_up ->
+            RateLimiter.call(conn, opts)
+        end
+      end)
+
+    task2 =
+      Task.async(fn ->
+        send(pid1, :process2_up)
+        RateLimiter.call(conn_2, opts)
+      end)
+
+    Task.await(task1)
+    Task.await(task2)
+
+    refute {:err, :not_found} == RateLimiter.inspect_bucket(conn, limiter_name, opts)
+  end
 end