Introduce rabbitmq-diagnostics maybe_stuck

Fixes #144.
[Finished ##135678977]

lib/rabbitmq/cli/diagnostics/commands/maybe_stuck_command.ex

@@ -0,0 +1,39 @@
+## The contents of this file are subject to the Mozilla Public License
+## Version 1.1 (the "License"); you may not use this file except in
+## compliance with the License. You may obtain a copy of the License
+## at http://www.mozilla.org/MPL/
+##
+## Software distributed under the License is distributed on an "AS IS"
+## basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+## the License for the specific language governing rights and
+## limitations under the License.
+##
+## The Original Code is RabbitMQ.
+##
+## The Initial Developer of the Original Code is GoPivotal, Inc.
+## Copyright (c) 2007-2016 Pivotal Software, Inc.  All rights reserved.
+
+
+defmodule RabbitMQ.CLI.Diagnostics.Commands.MaybeStuckCommand do
+  @behaviour RabbitMQ.CLI.CommandBehaviour
+  use RabbitMQ.CLI.DefaultOutput
+
+  def merge_defaults(args, opts), do: {args, opts}
+
+  def switches(), do: []
+
+  def validate(args, _) when length(args) > 0 do
+    {:validation_failure, :too_many_args}
+  end
+  def validate(_, _), do: :ok
+
+  def usage, do: "maybe_stuck"
+
+  def run([], %{node: node_name, timeout: timeout}) do
+    :rabbit_misc.rpc_call(node_name, :rabbit_diagnostics, :maybe_stuck, [], timeout)
+  end
+
+  def banner(_, %{node: node_name}) do
+    "Asking node #{node_name} to detect potentially stuck Erlang processes..."
+  end
+end

test/diagnostics/maybe_stuck_command_test.exs

@@ -0,0 +1,61 @@
+## The contents of this file are subject to the Mozilla Public License
+## Version 1.1 (the "License"); you may not use this file except in
+## compliance with the License. You may obtain a copy of the License
+## at http://www.mozilla.org/MPL/
+##
+## Software distributed under the License is distributed on an "AS IS"
+## basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+## the License for the specific language governing rights and
+## limitations under the License.
+##
+## The Original Code is RabbitMQ.
+##
+## The Initial Developer of the Original Code is GoPivotal, Inc.
+## Copyright (c) 2007-2016 Pivotal Software, Inc.  All rights reserved.
+
+
+defmodule MaybeStuckCommandTest do
+  use ExUnit.Case
+  import TestHelper
+
+  @command RabbitMQ.CLI.Diagnostics.Commands.MaybeStuckCommand
+
+  setup_all do
+    RabbitMQ.CLI.Core.Distribution.start()
+    :net_kernel.connect_node(get_rabbit_hostname)
+
+    on_exit([], fn ->
+      :erlang.disconnect_node(get_rabbit_hostname)
+
+    end)
+
+    :ok
+  end
+
+  setup context do
+    {:ok, opts: %{
+        node: get_rabbit_hostname,
+        timeout: context[:test_timeout] || 15
+      }}
+  end
+
+  test "merge_defaults: returns inputs" do
+    assert @command.merge_defaults([], %{timeout: 30}) == {[], %{timeout: 30}}
+  end
+
+  test "validate: treats positional arguments as a failure" do
+    assert @command.validate(["extra-arg"], %{}) == {:validation_failure, :too_many_args}
+  end
+
+  test "validate: treats empty positional arguments and default switches as a success" do
+    assert @command.validate([], %{}) == :ok
+  end
+
+  @tag test_timeout: 0
+  test "run: targeting an unreachable node throws a badrpc", context do
+    target = :jake@thedog
+    :net_kernel.connect_node(target)
+    opts = %{node: target}
+    assert @command.run([], Map.merge(context[:opts], opts)) == {:badrpc, :nodedown}
+  end
+end