Optimize rabbitmqctl startup.

Plugins dirs are added to ERL_LIBS by shell scripts, we try to load
enabled plugins first and scan plugins dir only if some of them
are not found.
When discovering plugins, we can load applications only for enabled ones.
EPMD can be started only after initial `net_kernel:start` call failed.
We don't need to discover all commands every time, only if a command is not
in the `rabbitmqctl` application modules.
[finishes #143025009]

deps/rabbitmq_cli/lib/rabbitmq/cli/core/command_modules.ex

@@ -20,12 +20,20 @@ alias RabbitMQ.CLI.Core.Helpers, as: Helpers
 defmodule RabbitMQ.CLI.Core.CommandModules do
   @commands_ns ~r/RabbitMQ.CLI.(.*).Commands/
 
-  def module_map do
-    Application.get_env(:rabbitmqctl, :commands) || load(%{})
+  def module_map(opts \\ %{}) do
+    Application.get_env(:rabbitmqctl, :commands) || load(opts)
   end
 
-  def is_command?([head | _]), do: is_command?(head)
-  def is_command?(str), do: module_map()[str] != nil
+  def module_map_core(opts \\ %{}) do
+    Application.get_env(:rabbitmqctl, :commands_core) || load_core(opts)
+  end
+
+  def load_core(opts) do
+    scope = script_scope(opts)
+    commands = load_commands_core(scope)
+    Application.put_env(:rabbitmqctl, :commands_core, commands)
+    commands
+  end
 
   def load(opts) do
     scope = script_scope(opts)
@@ -39,8 +47,47 @@ defmodule RabbitMQ.CLI.Core.CommandModules do
     scopes[Config.get_option(:script_name, opts)] || :none
   end
 
+  def load_commands_core(scope) do
+    make_module_map(ctl_modules(), scope)
+  end
+
   def load_commands(scope, opts) do
-    ctl_and_plugin_modules(opts)
+    make_module_map(plugin_modules(opts) ++ ctl_modules(), scope)
+  end
+
+  def ctl_modules() do
+    Application.spec(:rabbitmqctl, :modules)
+  end
+
+  def plugin_modules(opts) do
+    Helpers.require_rabbit(opts)
+
+    partitioned =
+      Enum.group_by(PluginsHelpers.read_enabled(opts), fn(app) ->
+        case Application.load(app) do
+          :ok -> :loaded;
+          {:error, {:already_loaded, ^app}} -> :loaded;
+          _ -> :not_found
+        end
+      end)
+
+    loaded = partitioned[:loaded] || []
+    missing = partitioned[:not_found] || []
+    ## If plugins are not in ERL_LIBS, they should be loaded from plugins_dir
+    case missing do
+      [] -> :ok;
+      _  ->
+        Helpers.add_plugins_to_load_path(opts)
+        Enum.each(missing, fn(app) -> Application.load(app) end)
+    end
+
+    Enum.flat_map(loaded ++ missing, fn(app) ->
+      Application.spec(app, :modules) || []
+    end)
+  end
+
+  defp make_module_map(modules, scope) do
+    modules
     |> Enum.filter(fn(mod) ->
                      to_string(mod) =~ @commands_ns
                      and
@@ -54,13 +101,6 @@ defmodule RabbitMQ.CLI.Core.CommandModules do
     |> Map.new
   end
 
-  def ctl_and_plugin_modules(opts) do
-    Helpers.require_rabbit_and_plugins(opts)
-    enabled_plugins = PluginsHelpers.read_enabled(opts)
-    [:rabbitmqctl | enabled_plugins]
-    |> Enum.flat_map(fn(app) -> Application.spec(app, :modules) || [] end)
-  end
-
   defp module_exists?(nil) do
     false
   end

deps/rabbitmq_cli/lib/rabbitmq/cli/core/distribution.ex

@@ -26,14 +26,25 @@ defmodule RabbitMQ.CLI.Core.Distribution do
 
   def start(options) do
     node_name_type = Config.get_option(:longnames, options)
-    :rabbit_nodes.ensure_epmd()
     start(node_name_type, 10, :undefined)
   end
 
-  def start_as(node_name, opts) do
-    :rabbit_nodes.ensure_epmd()
-    node_name_type = Config.get_option(:longnames, opts)
-    :net_kernel.start([node_name, node_name_type])
+  def start_as(node_name, options) do
+    node_name_type = Config.get_option(:longnames, options)
+    start_with_epmd(node_name, node_name_type)
+  end
+
+  ## Optimization. We try to start EPMD only if distribution fails
+  def start_with_epmd(node_name, node_name_type) do
+    case :net_kernel.start([node_name, node_name_type]) do
+      {:ok, _} = ok -> ok;
+      {:error, {:already_started, _}} = started -> started;
+      {:error, {{:already_started, _}, _}} = started -> started;
+      ## EPMD can be stopped. Retry with EPMD
+      {:error, _} ->
+        :rabbit_nodes.ensure_epmd()
+        :net_kernel.start([node_name, node_name_type])
+    end
   end
 
   #
@@ -46,7 +57,7 @@ defmodule RabbitMQ.CLI.Core.Distribution do
 
   defp start(node_name_type, attempts, _last_err) do
     candidate = generate_cli_node_name(node_name_type)
-    case :net_kernel.start([candidate, node_name_type]) do
+    case start_with_epmd(candidate, node_name_type) do
       {:ok, _} -> :ok
       {:error, {:already_started, pid}}      -> {:ok, pid};
       {:error, {{:already_started, pid}, _}} -> {:ok, pid};

deps/rabbitmq_cli/lib/rabbitmq/cli/core/helpers.ex

@@ -97,17 +97,13 @@ defmodule RabbitMQ.CLI.Core.Helpers do
     end
   end
 
-  def require_rabbit(opts) do
-    try_load_rabbit_code(opts)
-  end
-
   def require_rabbit_and_plugins(opts) do
-    with :ok <- try_load_rabbit_code(opts),
-         :ok <- try_load_rabbit_plugins(opts),
+    with :ok <- require_rabbit(opts),
+         :ok <- add_plugins_to_load_path(opts),
          do: :ok
   end
 
-  defp try_load_rabbit_code(opts) do
+  def require_rabbit(opts) do
     home = Config.get_option(:rabbitmq_home, opts)
     case home do
       nil ->
@@ -128,50 +124,56 @@ defmodule RabbitMQ.CLI.Core.Helpers do
     end
   end
 
-  defp try_load_rabbit_plugins(opts) do
+  def add_plugins_to_load_path(opts) do
     with {:ok, plugins_dir} <- plugins_dir(opts)
     do
       String.split(to_string(plugins_dir), separator())
       |>
-      Enum.map(&try_load_plugins_from_directory/1)
+      Enum.map(&add_directory_plugins_to_load_path/1)
       :ok
     end
   end
 
-  defp try_load_plugins_from_directory(directory_with_plugins_inside_it) do
+  def add_directory_plugins_to_load_path(directory_with_plugins_inside_it) do
     with {:ok, files} <- File.ls(directory_with_plugins_inside_it)
     do
-        Enum.filter_map(files,
-            fn(filename) -> String.ends_with?(filename, [".ez"]) end,
-          fn(archive) ->
-            ## Check that the .app file is present and take the app name from there
-            {:ok, ez_files} = :zip.list_dir(String.to_charlist(Path.join([directory_with_plugins_inside_it, archive])))
-            case find_dot_app(ez_files) do
-              :not_found -> :ok
-              dot_app ->
-                app_name = Path.basename(dot_app, ".app")
-                ebin_dir = Path.join([directory_with_plugins_inside_it, Path.dirname(dot_app)])
-                ebin_dir |> Code.append_path()
-                app_name |> String.to_atom() |> Application.load()
-            end
-          end)
+      Enum.map(files,
+        fn(filename) ->
+          cond do
+            String.ends_with?(filename, [".ez"]) ->
+              Path.join([directory_with_plugins_inside_it, filename])
+              |> String.to_charlist
+              |> add_archive_code_path();
+            File.dir?(filename) ->
+              Path.join([directory_with_plugins_inside_it, filename])
+              |> add_dir_code_path();
+            true ->
+              {:error, {:not_a_plugin, filename}}
+          end
+        end)
     end
   end
 
-  defp find_dot_app([head | tail]) when Record.is_record(head, :zip_file) do
-    name = :erlang.element(2, head)
-    case Regex.match?(~r/(.+)\/ebin\/(.+)\.app$/, to_string name) do
-      true ->
-        name
-      false ->
-        find_dot_app(tail)
+  defp add_archive_code_path(ez_dir) do
+    case :erl_prim_loader.list_dir(ez_dir) do
+      {:ok, [app_dir]} ->
+        app_in_ez = :filename.join(ez_dir, app_dir)
+        add_dir_code_path(app_in_ez);
+      _ -> {:error, :no_app_dir}
     end
   end
-  defp find_dot_app([_head | tail]) do
-    find_dot_app(tail)
-  end
-  defp find_dot_app([]) do
-    :not_found
+
+  defp add_dir_code_path(app_dir) do
+    case :erl_prim_loader.list_dir(app_dir) do
+      {:ok, list} ->
+        case Enum.member?(list, 'ebin') do
+          true ->
+            ebin_dir = :filename.join(app_dir, 'ebin')
+            Code.append_path(ebin_dir)
+          false -> {:error, :no_ebin}
+        end;
+      _ -> {:error, :app_dir_empty}
+    end
   end
 
   def require_mnesia_dir(opts) do

deps/rabbitmq_cli/lib/rabbitmq/cli/core/parser.ex

@@ -30,8 +30,6 @@ defmodule RabbitMQ.CLI.Core.Parser do
 
   def parse(input) do
     {parsed_args, options, invalid} = parse_global(input)
-    CommandModules.load(options)
-
     {command_name, command_module, arguments} = look_up_command(parsed_args, options)
 
     case command_module do
@@ -53,10 +51,20 @@ defmodule RabbitMQ.CLI.Core.Parser do
   defp look_up_command(parsed_args, options) do
     case parsed_args do
       [cmd_name | arguments] ->
-        module_map = CommandModules.module_map
-        command = module_map[cmd_name] ||
-                  command_alias(cmd_name, module_map, options) ||
-                  command_suggestion(cmd_name, module_map)
+        ## This is an optimisation for pluggable command discovery.
+        ## Most of the time a command will be from rabbitmqctl application
+        ## so there is not point in scanning plugins for potential commands
+        CommandModules.load_core(options)
+        core_commands = CommandModules.module_map_core
+        command = case core_commands[cmd_name] do
+          nil ->
+            CommandModules.load(options)
+            module_map = CommandModules.module_map
+            module_map[cmd_name] ||
+              command_alias(cmd_name, module_map, options) ||
+              command_suggestion(cmd_name, module_map);
+          c -> c
+        end
         {cmd_name, command, arguments}
       [] ->
         {"", nil, []}

deps/rabbitmq_cli/lib/rabbitmq/cli/ctl/commands/help_command.ex

@@ -28,14 +28,14 @@ defmodule RabbitMQ.CLI.Ctl.Commands.HelpCommand do
   def scopes(), do: [:ctl, :diagnostics, :plugins]
 
   def run([command_name], opts) do
-    case CommandModules.is_command?(command_name) do
-      true  ->
-        command = CommandModules.module_map[command_name]
+    CommandModules.load(opts)
+    case CommandModules.module_map[command_name] do
+      nil ->
+        all_usage(opts);
+      command ->
         Enum.join([base_usage(command, opts)] ++
                   options_usage() ++
-                  input_types(command), "\n");
-      false ->
-        all_usage(opts)
+                  input_types(command), "\n")
     end
   end
   def run(_, opts) do
@@ -51,6 +51,7 @@ defmodule RabbitMQ.CLI.Ctl.Commands.HelpCommand do
   end
 
   def all_usage(opts) do
+    CommandModules.load(opts)
     Enum.join(tool_usage(program_name(opts)) ++
               options_usage() ++
               commands() ++

deps/rabbitmq_cli/lib/rabbitmqctl.ex

@@ -35,8 +35,7 @@ defmodule RabbitMQCtl do
     auto_complete(script_basename, args)
   end
   def main(unparsed_command) do
-    unparsed_command
-    |> exec_command(fn(command, output, options) ->
+    exec_command(unparsed_command, fn(command, output, options) ->
         formatter = get_formatter(command, options)
         printer = get_printer(options)
 

deps/rabbitmq_cli/test/command_modules_test.exs

@@ -110,45 +110,6 @@ defmodule CommandModulesTest do
 
   end
 
-  ## ------------------- is_command?/1 tests --------------------
-
-  test "a valid implemented command returns true" do
-    set_scope(:ctl)
-    @subject.load(%{})
-    assert @subject.is_command?("status") == true
-  end
-
-  test "an invalid command returns false" do
-    set_scope(:ctl)
-    @subject.load(%{})
-    assert @subject.is_command?("quack") == false
-  end
-
-  test "a nil returns false" do
-    set_scope(:ctl)
-    @subject.load(%{})
-    assert @subject.is_command?(nil) == false
-  end
-
-  test "an empty array returns false" do
-    set_scope(:ctl)
-    @subject.load(%{})
-    assert @subject.is_command?([]) == false
-  end
-
-  test "an non-empty array tests the first element" do
-    set_scope(:ctl)
-    @subject.load(%{})
-    assert @subject.is_command?(["status", "quack"]) == true
-    assert @subject.is_command?(["quack", "status"]) == false
-  end
-
-  test "a non-string list returns false" do
-    set_scope(:ctl)
-    @subject.load(%{})
-    assert @subject.is_command?([{"status", "quack"}, {4, "Fantastic"}]) == false
-  end
-
   ## ------------------- commands/0 tests --------------------
 
   test "command_modules has existing commands" do

deps/rabbitmq_cli/test/core/helpers_test.exs

@@ -118,23 +118,25 @@ test "RabbitMQ hostname is properly formed" do
 
   ## ------------------- require_rabbit/1 tests --------------------
 
-  test "load plugin with version number in filename" do
+  test "locate plugin with version number in filename" do
     plugins_directory_03 = fixture_plugins_path("plugins-subdirectory-03")
     rabbitmq_home = :rabbit_misc.rpc_call(node(), :code, :lib_dir, [:rabbit])
     opts = %{plugins_dir: to_string(plugins_directory_03),
              rabbitmq_home: rabbitmq_home}
     assert Enum.member?(Application.loaded_applications(), {:mock_rabbitmq_plugins_03, 'New project', '0.1.0'}) == false
     @subject.require_rabbit_and_plugins(opts)
+    Application.load(:mock_rabbitmq_plugins_03)
     assert Enum.member?(Application.loaded_applications(), {:mock_rabbitmq_plugins_03, 'New project', '0.1.0'})
   end
 
-  test "load plugin without version number in filename" do
+  test "locate plugin without version number in filename" do
     plugins_directory_04 = fixture_plugins_path("plugins-subdirectory-04")
     rabbitmq_home = :rabbit_misc.rpc_call(node(), :code, :lib_dir, [:rabbit])
     opts = %{plugins_dir: to_string(plugins_directory_04),
              rabbitmq_home: rabbitmq_home}
     assert Enum.member?(Application.loaded_applications(), {:mock_rabbitmq_plugins_04, 'New project', 'rolling'}) == false
     @subject.require_rabbit_and_plugins(opts)
+    Application.load(:mock_rabbitmq_plugins_04)
     assert Enum.member?(Application.loaded_applications(), {:mock_rabbitmq_plugins_04, 'New project', 'rolling'})
   end