fix(mint): prevent duplicate retries on graceful shutdown

grpc/lib/grpc/client/adapters/mint/connection_process/connection_process.ex

@@ -445,7 +445,12 @@ if Code.ensure_loaded?(Mint.HTTP) do
       clean_state = State.update_request_stream_queue(%{new_state | requests: %{}}, :queue.new())
 
       if clean_state.retry > 0 do
-        attempt_reconnect(clean_state)
+        # A failed attempt already scheduled the next retry; ignore duplicate close events.
+        if clean_state.retry_attempt > 0 do
+          {:noreply, clean_state}
+        else
+          attempt_reconnect(clean_state)
+        end
       else
         send(clean_state.parent, {:elixir_grpc, :connection_down, self()})
         {:stop, :normal, clean_state}

grpc/test/grpc/adapters/mint/connection_process_test.exs

@@ -439,6 +439,35 @@ defmodule GRPC.Client.Adapters.Mint.ConnectionProcessTest do
     end
   end
 
+  describe "handle_info - duplicate connection close notifications" do
+    @describetag private_endpoint: ReconnectUnavailableEndpoint
+    setup :start_private_endpoint
+    setup :valid_connection_with_retry
+
+    test "does not start another retry chain after GOAWAY and tcp_closed", %{
+      process_pid: pid
+    } do
+      wait_until_open(pid)
+      state = :sys.get_state(pid)
+      :ok = GRPC.Server.stop_endpoint(ReconnectUnavailableEndpoint)
+
+      goaway_frame = <<8::24, 0x07, 0, 0::32, 0::32, 0::32>>
+      goaway = {:tcp, state.conn.socket, goaway_frame}
+      closed = {:tcp_closed, state.conn.socket}
+      unavailable_state = %{state | retry_timeout_ms: 60_000}
+
+      assert {:noreply, retrying_state} =
+               ConnectionProcess.handle_info(goaway, unavailable_state)
+
+      assert retrying_state.retry_attempt == 1
+
+      assert {:noreply, still_retrying_state} =
+               ConnectionProcess.handle_info(closed, retrying_state)
+
+      assert still_retrying_state.retry_attempt == 1
+    end
+  end
+
   describe "handle_info - connection_closed - with retry - exhausted" do
     @describetag private_endpoint: ReconnectExhaustedEndpoint
     setup :start_private_endpoint