Ensure handle_demand busy wait infinite loop doesn't occur & deprecate message_child

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## 1.1.0-rc0
  * Deprecate `handle_spec_started/3` callback in Bins and Pipelines. [#708](https://github.com/membraneframework/membrane_core/pull/708)
  * Handle buffers from input pads having `flow_control: :auto` only if demand on all output pads having `flow_control: :auto` is positive. [#693](https://github.com/membraneframework/membrane_core/pull/693)
+ * Deprecate `Membrane.Testing.Pipeline.message_child/3`. Introduce `Membrane.Testing.Pipeline.notify_child/3` instead. [#779](https://github.com/membraneframework/membrane_core/pull/779)
 
 ## 1.0.1
  * Specify the order in which state fields will be printed in the error logs. [#614](https://github.com/membraneframework/membrane_core/pull/614)

lib/membrane/core/element.ex

@@ -137,33 +137,17 @@ defmodule Membrane.Core.Element do
         module: options.module,
         type: options.module.membrane_element_type(),
         name: options.name,
-        internal_state: nil,
         parent_pid: options.parent,
-        supplying_demand?: false,
-        delayed_demands: MapSet.new(),
-        handle_demand_loop_counter: 0,
         synchronization: %{
           parent_clock: options.parent_clock,
           timers: %{},
           clock: nil,
           stream_sync: options.sync,
           latency: 0
         },
-        initialized?: false,
-        playback: :stopped,
-        playback_queue: [],
         resource_guard: resource_guard,
         subprocess_supervisor: options.subprocess_supervisor,
-        terminating?: false,
-        setup_incomplete?: false,
-        effective_flow_control: :push,
-        handling_action?: false,
-        popping_auto_flow_queue?: false,
-        pads_to_snapshot: MapSet.new(),
-        stalker: options.stalker,
-        satisfied_auto_output_pads: MapSet.new(),
-        awaiting_auto_input_pads: MapSet.new(),
-        auto_input_pads: []
+        stalker: options.stalker
       }
       |> PadSpecHandler.init_pads()
 
@@ -226,8 +210,8 @@ defmodule Membrane.Core.Element do
     {:noreply, state}
   end
 
-  defp do_handle_info(Message.new(:resume_handle_demand_loop), state) do
-    state = DemandHandler.handle_delayed_demands(state)
+  defp do_handle_info(Message.new(:resume_delayed_demands_loop), state) do
+    state = DemandHandler.resume_delayed_demands_loop(state)
     {:noreply, state}
   end
 

lib/membrane/core/element/demand_handler.ex

@@ -113,6 +113,12 @@ defmodule Membrane.Core.Element.DemandHandler do
     PadModel.set_data!(state, pad_ref, :manual_demand_size, new_manual_demand_size)
   end
 
+  @spec resume_delayed_demands_loop(State.t()) :: State.t()
+  def resume_delayed_demands_loop(%State{} = state) do
+    %{state | resume_delayed_demands_loop_in_mailbox?: false}
+    |> handle_delayed_demands()
+  end
+
   @spec handle_delayed_demands(State.t()) :: State.t()
   def handle_delayed_demands(%State{} = state) do
     # Taking random element of `:delayed_demands` is done to keep data flow
@@ -125,10 +131,15 @@ defmodule Membrane.Core.Element.DemandHandler do
         raise "Cannot handle delayed demands while already supplying demand"
 
       state.handle_demand_loop_counter >= @handle_demand_loop_limit ->
-        Message.self(:resume_handle_demand_loop)
+        state =
+          with %{resume_delayed_demands_loop_in_mailbox?: false} <- state do
+            Message.self(:resume_delayed_demands_loop)
+            %{state | resume_delayed_demands_loop_in_mailbox?: true}
+          end
+
         %{state | handle_demand_loop_counter: 0}
 
-      Enum.empty?(state.delayed_demands) ->
+      MapSet.size(state.delayed_demands) == 0 ->
         %{state | handle_demand_loop_counter: 0}
 
       true ->

lib/membrane/core/element/state.ex

@@ -47,7 +47,8 @@ defmodule Membrane.Core.Element.State do
           pads_to_snapshot: MapSet.t(),
           stalker: Membrane.Core.Stalker.t(),
           satisfied_auto_output_pads: MapSet.t(),
-          awaiting_auto_input_pads: MapSet.t()
+          awaiting_auto_input_pads: MapSet.t(),
+          resume_delayed_demands_loop_in_mailbox?: boolean()
         }
 
   # READ THIS BEFORE ADDING NEW FIELD!!!
@@ -59,34 +60,32 @@ defmodule Membrane.Core.Element.State do
   # as the last item in the list, because sometimes it is so big, that everything after it
   # might be truncated during the inspection.
 
-  defstruct [
-    :module,
-    :name,
-    :parent_pid,
-    :playback,
-    :type,
-    :internal_state,
-    :pad_refs,
-    :pads_info,
-    :synchronization,
-    :delayed_demands,
-    :effective_flow_control,
-    :initialized?,
-    :terminating?,
-    :setup_incomplete?,
-    :supplying_demand?,
-    :handling_action?,
-    :popping_auto_flow_queue?,
-    :stalker,
-    :resource_guard,
-    :subprocess_supervisor,
-    :handle_demand_loop_counter,
-    :demand_size,
-    :pads_to_snapshot,
-    :playback_queue,
-    :pads_data,
-    :satisfied_auto_output_pads,
-    :awaiting_auto_input_pads,
-    :auto_input_pads
-  ]
+  defstruct module: nil,
+            name: nil,
+            parent_pid: nil,
+            playback: :stopped,
+            type: nil,
+            internal_state: nil,
+            pad_refs: [],
+            pads_info: %{},
+            synchronization: nil,
+            delayed_demands: MapSet.new(),
+            effective_flow_control: :push,
+            initialized?: false,
+            terminating?: false,
+            setup_incomplete?: false,
+            supplying_demand?: false,
+            handling_action?: false,
+            popping_auto_flow_queue?: false,
+            stalker: nil,
+            resource_guard: nil,
+            subprocess_supervisor: nil,
+            handle_demand_loop_counter: 0,
+            pads_to_snapshot: MapSet.new(),
+            playback_queue: [],
+            pads_data: %{},
+            satisfied_auto_output_pads: MapSet.new(),
+            awaiting_auto_input_pads: MapSet.new(),
+            auto_input_pads: [],
+            resume_delayed_demands_loop_in_mailbox?: false
 end

lib/membrane/testing/pipeline.ex

@@ -52,7 +52,7 @@ defmodule Membrane.Testing.Pipeline do
   ## Messaging children
 
   You can send messages to children using their names specified in the children
-  list. Please check `message_child/3` for more details.
+  list. Please check `notify_child/3` for more details.
 
   ## Example usage
 
@@ -202,6 +202,23 @@ defmodule Membrane.Testing.Pipeline do
   defdelegate terminate(pipeline, opts \\ []), to: Pipeline
 
   @doc """
+  Sends notification to a child by Element name.
+
+  ## Example
+
+  Knowing that `pipeline` has child named `sink`, notification can be sent as follows:
+
+      notify_child(pipeline, :sink, {:notification, "to handle"})
+  """
+  @spec notify_child(pid(), Element.name(), any()) :: :ok
+  def notify_child(pipeline, child, notification) do
+    send(pipeline, {:for_element, child, notification})
+    :ok
+  end
+
+  @doc """
+  Deprecated since `v1.1.0-rc0`, use `notify_child/3` instead.
+
   Sends message to a child by Element name.
 
   ## Example
@@ -210,10 +227,10 @@ defmodule Membrane.Testing.Pipeline do
 
       message_child(pipeline, :sink, {:message, "to handle"})
   """
+  @deprecated "Use #{inspect(__MODULE__)}.notify_child/3 instead"
   @spec message_child(pid(), Element.name(), any()) :: :ok
   def message_child(pipeline, child, message) do
-    send(pipeline, {:for_element, child, message})
-    :ok
+    notify_child(pipeline, child, message)
   end
 
   @doc """

test/membrane/integration/actions_handling_order_test.exs

@@ -176,7 +176,7 @@ defmodule Membrane.Integration.ActionsHandlingOrderTest do
     # time for pipeline to play
     Process.sleep(100)
 
-    Testing.Pipeline.message_child(pipeline, :sink, :start_timer)
+    Testing.Pipeline.notify_child(pipeline, :sink, :start_timer)
 
     assert_pipeline_notified(pipeline, :sink, :second_tick)
 

test/membrane/integration/auto_demands_test.exs

@@ -129,7 +129,7 @@ defmodule Membrane.Integration.AutoDemandsTest do
 
     assert_sink_playing(pipeline, :right_sink)
 
-    Pipeline.message_child(pipeline, :right_sink, {:make_demand, 1000})
+    Pipeline.notify_child(pipeline, :right_sink, {:make_demand, 1000})
 
     Enum.each(1..1000, fn payload ->
       assert_sink_buffer(pipeline, :right_sink, buffer)
@@ -246,15 +246,15 @@ defmodule Membrane.Integration.AutoDemandsTest do
     assert_pipeline_notified(pipeline, :source, :playing)
 
     buffers = Enum.map(1..10, &%Membrane.Buffer{payload: &1})
-    Pipeline.message_child(pipeline, :source, buffer: {:output, buffers})
+    Pipeline.notify_child(pipeline, :source, buffer: {:output, buffers})
 
     Enum.each(1..100_010, fn i ->
       assert_sink_buffer(pipeline, :sink, buffer)
       assert buffer.payload == i
 
       if i <= 100_000 do
         buffer = %Membrane.Buffer{payload: i + 10}
-        Pipeline.message_child(pipeline, :source, buffer: {:output, buffer})
+        Pipeline.notify_child(pipeline, :source, buffer: {:output, buffer})
       end
     end)
 
@@ -276,7 +276,7 @@ defmodule Membrane.Integration.AutoDemandsTest do
     assert_pipeline_notified(pipeline, :source, :playing)
 
     buffers = Enum.map(1..100_000, &%Membrane.Buffer{payload: &1})
-    Pipeline.message_child(pipeline, :source, buffer: {:output, buffers})
+    Pipeline.notify_child(pipeline, :source, buffer: {:output, buffers})
 
     assert_receive(
       {:DOWN, _ref, :process, ^pipeline, {:membrane_child_crash, :sink, _sink_reason}}
@@ -347,7 +347,7 @@ defmodule Membrane.Integration.AutoDemandsTest do
       assert length(buffers) == manual_flow_queue_size
 
       demand = 10_000
-      Pipeline.message_child(pipeline, :sink, {:make_demand, demand})
+      Pipeline.notify_child(pipeline, :sink, {:make_demand, demand})
 
       buffers = receive_processed_buffers(pipeline, 2 * demand)
       buffers_number = length(buffers)
@@ -379,7 +379,7 @@ defmodule Membrane.Integration.AutoDemandsTest do
 
       assert_pipeline_notified(pipeline, :filter, :playing)
 
-      Pipeline.message_child(pipeline, :filter, pause_auto_demand: Pad.ref(:input, 0))
+      Pipeline.notify_child(pipeline, :filter, pause_auto_demand: Pad.ref(:input, 0))
 
       # time for :filter to pause demand on Pad.ref(:input, 0)
       Process.sleep(500)
@@ -388,7 +388,7 @@ defmodule Membrane.Integration.AutoDemandsTest do
       assert length(buffers) == manual_flow_queue_size
 
       demand = 10_000
-      Pipeline.message_child(pipeline, :sink, {:make_demand, demand})
+      Pipeline.notify_child(pipeline, :sink, {:make_demand, demand})
 
       # fliter paused auto demand on Pad.ref(:input, 0), so it should receive
       # at most auto_flow_demand_size buffers from there and rest of the buffers
@@ -410,12 +410,12 @@ defmodule Membrane.Integration.AutoDemandsTest do
       # rest of them came from {:source, 1}
       assert demand - auto_flow_demand_size <= counter_1
 
-      Pipeline.message_child(pipeline, :filter, resume_auto_demand: Pad.ref(:input, 0))
+      Pipeline.notify_child(pipeline, :filter, resume_auto_demand: Pad.ref(:input, 0))
 
       # time for :filter to resume demand on Pad.ref(:input, 0)
       Process.sleep(500)
 
-      Pipeline.message_child(pipeline, :sink, {:make_demand, demand})
+      Pipeline.notify_child(pipeline, :sink, {:make_demand, demand})
 
       buffers = receive_processed_buffers(pipeline, 2 * demand)
       buffers_number = length(buffers)

test/membrane/integration/delayed_demands_loop_test.exs

@@ -0,0 +1,83 @@
+defmodule Membrane.Test.DelayedDemandsLoopTest do
+  use ExUnit.Case, async: true
+
+  import Membrane.ChildrenSpec
+  import Membrane.Testing.Assertions
+
+  alias Membrane.Buffer
+  alias Membrane.Debug
+  alias Membrane.Testing
+
+  defmodule Source do
+    use Membrane.Source
+
+    defmodule StreamFormat do
+      defstruct []
+    end
+
+    @sleep_time 5
+
+    def_output_pad :output,
+      accepted_format: _any,
+      availability: :on_request,
+      flow_control: :manual
+
+    @impl true
+    def handle_demand(_pad, _size, :buffers, %{pads: pads}, state) do
+      Process.sleep(@sleep_time)
+
+      stream_format_actions =
+        Enum.flat_map(pads, fn
+          {pad_ref, %{start_of_stream?: false}} -> [stream_format: {pad_ref, %StreamFormat{}}]
+          _pad_entry -> []
+        end)
+
+      buffer = %Buffer{payload: "a"}
+
+      buffer_and_redemand_actions =
+        Map.keys(pads)
+        |> Enum.flat_map(&[buffer: {&1, buffer}, redemand: &1])
+
+      {stream_format_actions ++ buffer_and_redemand_actions, state}
+    end
+
+    @impl true
+    def handle_parent_notification(:request, _ctx, state) do
+      {[notify_parent: :response], state}
+    end
+  end
+
+  describe "delayed demands loop pauses from time to time, when source has" do
+    test "1 pad", do: do_test(1)
+    test "2 pads", do: do_test(2)
+    test "10 pads", do: do_test(10)
+  end
+
+  defp do_test(sinks_number) do
+    # auto_demand_size is smaller than delayed_demands_loop_counter_limit, to ensure that
+    # after a snapshot, the counter is not reset
+    auto_demand_size = 15
+    requests_number = 20
+
+    spec =
+      [child(:source, Source)] ++
+        for i <- 1..sinks_number do
+          get_child(:source)
+          |> via_in(:input, auto_demand_size: auto_demand_size)
+          |> child({:sink, i}, Debug.Sink)
+        end
+
+    pipeline = Testing.Pipeline.start_link_supervised!(spec: spec)
+
+    for i <- 1..sinks_number do
+      assert_start_of_stream(pipeline, {:sink, ^i})
+    end
+
+    for _i <- 1..requests_number do
+      Testing.Pipeline.notify_child(pipeline, :source, :request)
+      assert_pipeline_notified(pipeline, :source, :response)
+    end
+
+    Testing.Pipeline.terminate(pipeline)
+  end
+end

test/membrane/integration/demands_test.exs

@@ -24,14 +24,14 @@ defmodule Membrane.Integration.DemandsTest do
     assert_sink_playing(pid, :sink)
 
     demand = 500
-    Pipeline.message_child(pid, :sink, {:make_demand, demand})
+    Pipeline.notify_child(pid, :sink, {:make_demand, demand})
 
     0..(demand - 1)
     |> assert_buffers_received(pid)
 
     pattern = %Buffer{payload: <<demand::16>> <> <<255>>}
     refute_sink_buffer(pid, :sink, ^pattern, 0)
-    Pipeline.message_child(pid, :sink, {:make_demand, demand})
+    Pipeline.notify_child(pid, :sink, {:make_demand, demand})
 
     demand..(2 * demand - 1)
     |> assert_buffers_received(pid)