Task: Implement caching mechanism (#364)

* add crashing component to dev

* add state_server

* update pub_sub

* add tests

Author: GuzekAlan

dev/live_components/crash.ex

@@ -0,0 +1,13 @@
+defmodule LiveDebuggerDev.LiveComponents.Crash do
+  use DevWeb, :live_component
+
+  def render(assigns) do
+    ~H"""
+    <div>
+      <.box title="Crash [LiveComponent]" color="red">
+        <.button phx-click="crash" color="red" phx-target={@myself}>Crash</.button>
+      </.box>
+    </div>
+    """
+  end
+end

dev/live_views/main.ex

@@ -58,6 +58,7 @@ defmodule LiveDebuggerDev.LiveViews.Main do
 
         <.live_component id="many_assigns" module={LiveComponents.ManyAssigns} />
         <.live_component id="name_outer" name={@name} module={LiveComponents.Name} />
+        <.live_component id="crash" module={LiveComponents.Crash} />
         <.live_component id="send_outer" module={LiveComponents.Send}>
           <.live_component id="name_inner" name={@name} module={LiveComponents.Name} />
           <.live_component id="long_name" module={LiveComponents.LiveComponentWithVeryVeryLongName} />

lib/live_debugger.ex

@@ -39,6 +39,7 @@ defmodule LiveDebugger do
     else
       children ++
         [
+          {LiveDebugger.GenServers.StateServer, []},
           {LiveDebugger.GenServers.CallbackTracingServer, []},
           {LiveDebugger.GenServers.EtsTableServer, []}
         ]

lib/live_debugger/gen_servers/callback_tracing_server.ex

@@ -177,23 +177,18 @@ defmodule LiveDebugger.GenServers.CallbackTracingServer do
 
   @spec do_publish(Trace.t()) :: :ok
   defp do_publish(%{module: Phoenix.LiveView.Diff} = trace) do
-    trace
-    |> PubSubUtils.component_deleted_topic()
-    |> PubSubUtils.broadcast({:new_trace, trace})
+    PubSubUtils.component_deleted_topic()
+    |> PubSubUtils.broadcast({:component_deleted, trace})
   end
 
-  defp do_publish(trace) do
+  defp do_publish(%Trace{} = trace) do
     socket_id = trace.socket_id
     node_id = Trace.node_id(trace)
     transport_pid = trace.transport_pid
     fun = trace.function
 
     socket_id
-    |> PubSubUtils.tsnf_topic(transport_pid, node_id, fun, :call)
-    |> PubSubUtils.broadcast({:new_trace, trace})
-
-    socket_id
-    |> PubSubUtils.ts_f_topic(transport_pid, fun)
+    |> PubSubUtils.trace_topic(transport_pid, node_id, fun, :call)
     |> PubSubUtils.broadcast({:new_trace, trace})
   end
 
@@ -204,8 +199,13 @@ defmodule LiveDebugger.GenServers.CallbackTracingServer do
     transport_pid = trace.transport_pid
     fun = trace.function
 
+    if fun == :render do
+      PubSubUtils.node_rendered_topic()
+      |> PubSubUtils.broadcast({:render_trace, trace})
+    end
+
     socket_id
-    |> PubSubUtils.tsnf_topic(transport_pid, node_id, fun, :return)
+    |> PubSubUtils.trace_topic(transport_pid, node_id, fun, :return)
     |> PubSubUtils.broadcast({:updated_trace, trace})
   end
 end

lib/live_debugger/gen_servers/ets_table_server.ex

@@ -21,37 +21,13 @@ defmodule LiveDebugger.GenServers.EtsTableServer do
   It creates table if none is associated with given pid
   """
   @spec table!(pid :: pid()) :: :ets.table()
-  def table!(pid) when is_pid(pid) do
-    impl().table!(pid)
-  end
+  def table!(pid) when is_pid(pid), do: impl().table!(pid)
 
   @doc """
   If table for given `pid` exists it deletes it from ETS.
   """
   @spec delete_table!(pid :: pid()) :: :ok
-  def delete_table!(pid) when is_pid(pid) do
-    impl().delete_table!(pid)
-  end
-
-  def impl() do
-    Application.get_env(:live_debugger, :ets_table_server, __MODULE__.Impl)
-  end
-
-  defmodule Impl do
-    @moduledoc false
-    @behaviour LiveDebugger.GenServers.EtsTableServer
-    @server_module LiveDebugger.GenServers.EtsTableServer
-
-    @impl true
-    def table!(pid) do
-      GenServer.call(@server_module, {:get_or_create_table, pid}, 1000)
-    end
-
-    @impl true
-    def delete_table!(pid) do
-      GenServer.call(@server_module, {:delete_table, pid}, 1000)
-    end
-  end
+  def delete_table!(pid) when is_pid(pid), do: impl().delete_table!(pid)
 
   ## GenServer
 
@@ -69,9 +45,8 @@ defmodule LiveDebugger.GenServers.EtsTableServer do
   def handle_info({:DOWN, _, :process, closed_pid, _}, table_refs) do
     {_, table_refs} = delete_ets_table(closed_pid, table_refs)
 
-    closed_pid
-    |> PubSubUtils.process_status_topic()
-    |> PubSubUtils.broadcast({:process_status, :dead})
+    PubSubUtils.process_status_topic()
+    |> PubSubUtils.broadcast({:process_status, {:dead, closed_pid}})
 
     {:noreply, table_refs}
   end
@@ -95,6 +70,26 @@ defmodule LiveDebugger.GenServers.EtsTableServer do
     {:reply, :ok, table_refs}
   end
 
+  defp impl() do
+    Application.get_env(:live_debugger, :ets_table_server, __MODULE__.Impl)
+  end
+
+  defmodule Impl do
+    @moduledoc false
+    @behaviour LiveDebugger.GenServers.EtsTableServer
+    @server_module LiveDebugger.GenServers.EtsTableServer
+
+    @impl true
+    def table!(pid) do
+      GenServer.call(@server_module, {:get_or_create_table, pid}, 1000)
+    end
+
+    @impl true
+    def delete_table!(pid) do
+      GenServer.call(@server_module, {:delete_table, pid}, 1000)
+    end
+  end
+
   @spec create_ets_table() :: :ets.table()
   defp create_ets_table() do
     :ets.new(@ets_table_name, [:ordered_set, :public])

lib/live_debugger/gen_servers/state_server.ex

@@ -0,0 +1,114 @@
+defmodule LiveDebugger.GenServers.StateServer do
+  @moduledoc """
+  This gen_server is responsible for storing the state of the application.
+  It collects state when `render` or `delete_component` callbacks are traced.
+  It uses named ETS table to store the state of the LiveView channel process.
+  When process dies, it removes the state from the table.
+  """
+
+  use GenServer
+
+  alias LiveDebugger.Services.System.ProcessService
+  alias LiveDebugger.Utils.PubSub, as: PubSubUtils
+  alias LiveDebugger.CommonTypes
+  alias LiveDebugger.Structs.Trace
+
+  @ets_table_name :lvdbg_states
+
+  @callback get(pid :: pid()) :: {:ok, CommonTypes.channel_state()} | {:error, term()}
+
+  @doc """
+  Returns previously stored state of the LiveView channel process identified by `pid`.
+  If the state is not found, it returns `{:error, :not_found}`.
+  """
+  @spec get(pid :: pid()) :: {:ok, CommonTypes.channel_state()} | {:error, term()}
+  def get(pid) when is_pid(pid) do
+    impl().get(pid)
+  end
+
+  @doc false
+  @spec ets_table_name() :: atom()
+  def ets_table_name(), do: @ets_table_name
+
+  @doc false
+  def record_id(pid), do: "#{inspect(pid)}"
+
+  @doc false
+  def start_link(args \\ []) do
+    GenServer.start_link(__MODULE__, args, name: __MODULE__)
+  end
+
+  @impl true
+  def init(_args) do
+    :ets.new(@ets_table_name, [:named_table, :public, :ordered_set])
+
+    PubSubUtils.node_rendered_topic()
+    |> PubSubUtils.subscribe!()
+
+    PubSubUtils.component_deleted_topic()
+    |> PubSubUtils.subscribe!()
+
+    PubSubUtils.process_status_topic()
+    |> PubSubUtils.subscribe!()
+
+    {:ok, []}
+  end
+
+  @impl true
+  def handle_info({:component_deleted, trace}, state) do
+    save_state(trace)
+
+    {:noreply, state}
+  end
+
+  def handle_info({:render_trace, trace}, state) do
+    save_state(trace)
+
+    {:noreply, state}
+  end
+
+  def handle_info({:process_status, {:dead, pid}}, state) do
+    :ets.delete(@ets_table_name, record_id(pid))
+
+    {:noreply, state}
+  end
+
+  defp save_state(%Trace{pid: pid} = trace) do
+    with {:ok, channel_state} <- ProcessService.state(pid) do
+      record_id = record_id(pid)
+      :ets.insert(@ets_table_name, {record_id, channel_state})
+
+      publish_state_changed(trace, channel_state)
+    end
+  end
+
+  defp publish_state_changed(%Trace{} = trace, channel_state) do
+    socket_id = trace.socket_id
+    transport_pid = trace.transport_pid
+    node_id = trace.cid || trace.pid
+
+    PubSubUtils.state_changed_topic(socket_id, transport_pid, node_id)
+    |> PubSubUtils.broadcast({:state_changed, channel_state, trace})
+
+    PubSubUtils.state_changed_topic(socket_id, transport_pid)
+    |> PubSubUtils.broadcast({:state_changed, channel_state, trace})
+  end
+
+  defp impl() do
+    Application.get_env(:live_debugger, :state_server, __MODULE__.Impl)
+  end
+
+  defmodule Impl do
+    @moduledoc false
+
+    @behaviour LiveDebugger.GenServers.StateServer
+    @server_module LiveDebugger.GenServers.StateServer
+
+    def get(pid) do
+      case :ets.lookup(@server_module.ets_table_name(), @server_module.record_id(pid)) do
+        [{_, channel_state}] -> {:ok, channel_state}
+        [] -> {:error, :not_found}
+      end
+    end
+  end
+end

lib/live_debugger/services/channel_service.ex

@@ -4,20 +4,15 @@ defmodule LiveDebugger.Services.ChannelService do
   """
 
   alias LiveDebugger.Structs.TreeNode
-  alias LiveDebugger.Services.System.ProcessService
   alias LiveDebugger.CommonTypes
+  alias LiveDebugger.GenServers.StateServer
 
   @doc """
   Retrieves the state of the LiveView channel process identified by `pid`.
   """
   @spec state(pid :: pid()) :: {:ok, CommonTypes.channel_state()} | {:error, term()}
   def state(pid) do
-    case ProcessService.state(pid) do
-      {:ok, %{socket: %Phoenix.LiveView.Socket{}, components: _} = state} -> {:ok, state}
-      {:ok, _} -> {:error, "PID: #{inspect(pid)} is not a LiveView process"}
-      {:error, :not_alive} -> {:error, :not_alive}
-      {:error, _} -> {:error, "Could not get state from pid: #{inspect(pid)}"}
-    end
+    StateServer.get(pid)
   end
 
   @doc """

lib/live_debugger/services/system/dbg_service.ex

@@ -29,28 +29,22 @@ defmodule LiveDebugger.Services.System.DbgService do
   @spec tracer(:process, handler_spec()) :: {:ok, pid()} | {:error, term()}
   @spec tracer(:module, module_spec()) :: {:ok, pid()} | {:error, term()}
   @spec tracer(:file, filename :: :file.name_all()) :: {:ok, pid()} | {:error, term()}
-  def tracer(type, handler_spec) do
-    impl().tracer(type, handler_spec)
-  end
+  def tracer(type, handler_spec), do: impl().tracer(type, handler_spec)
 
   @doc """
   Wrapper for `:dbg.p/2`.
   Traces `Item` in accordance to the value specified by `Flags`.
   `p` stands for **p**rocess.
   """
   @spec p(item :: term(), flags :: term()) :: {:ok, match_desc()} | {:error, term()}
-  def p(item, flags) do
-    impl().p(item, flags)
-  end
+  def p(item, flags), do: impl().p(item, flags)
 
   @doc """
   Wrapper for `:dbg.tp/2` that sets up a trace pattern.
   Enables call trace for one or more exported functions specified by `ModuleOrMFA`.
   """
   @spec tp(module() | mfa(), match_spec :: term()) :: {:ok, match_desc()} | {:error, term()}
-  def tp(module, match_spec) do
-    impl().tp(module, match_spec)
-  end
+  def tp(module, match_spec), do: impl().tp(module, match_spec)
 
   defp impl() do
     Application.get_env(

lib/live_debugger/structs/trace.ex

@@ -31,22 +31,22 @@ defmodule LiveDebugger.Structs.Trace do
 
   @type t() :: %__MODULE__{
           id: integer(),
-          module: atom(),
+          module: module(),
           function: atom(),
           arity: non_neg_integer(),
           args: list(),
           socket_id: String.t(),
           transport_pid: pid() | nil,
           pid: pid(),
           cid: struct() | nil,
-          timestamp: timestamp(),
+          timestamp: integer(),
           execution_time: non_neg_integer() | nil
         }
 
   @doc """
   Creates a new trace struct.
   """
-  @spec new(integer(), atom(), atom(), list(), pid(), timestamp(), Keyword.t()) :: t()
+  @spec new(integer(), module(), atom(), list(), pid(), timestamp(), Keyword.t()) :: t()
   def new(id, module, function, args, pid, timestamp, opts \\ []) do
     socket_id = Keyword.get(opts, :socket_id, get_socket_id_from_args(args))
     transport_pid = Keyword.get(opts, :transport_pid, get_transport_pid_from_args(args))