Integrate looking_glass

An Erlang/Elixir/BEAM profiler tool:
https://github.com/rabbitmq/looking_glass

Signed-off-by: Loïc Hoguin <loic@rabbitmq.com>

2 files changed, 51 insertions, 0 deletions

diff --git a/src/rabbit.erl b/src/rabbit.erl
index 93f5230250..033379bad1 100644
--- a/src/rabbit.erl
+++ b/src/rabbit.erl
@@ -200,6 +200,11 @@
                                    [rabbit_core_metrics_gc]}},
                     {enables,     networking}]}).
 
+-rabbit_boot_step({rabbit_looking_glass,
+                   [{description, "Looking Glass tracer and profiler"},
+                    {mfa,         {rabbit_looking_glass, boot, []}},
+                    {requires,    networking}]}).
+
 %%---------------------------------------------------------------------------
 
 -include("rabbit_framing.hrl").
diff --git a/src/rabbit_looking_glass.erl b/src/rabbit_looking_glass.erl
new file mode 100644
index 0000000000..702fb41eb8
--- /dev/null
+++ b/src/rabbit_looking_glass.erl
@@ -0,0 +1,46 @@
+%% 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) 2007-2017 Pivotal Software, Inc.  All rights reserved.
+%%
+
+-module(rabbit_looking_glass).
+
+-ignore_xref([{lg, trace, 4}]).
+
+-export([boot/0]).
+-export([connections/0]).
+
+boot() ->
+    case os:getenv("RABBITMQ_TRACER") of
+        false ->
+            ok;
+        Value ->
+            Input = parse_value(Value),
+            rabbit_log:info("Enabling Looking Glass profiler, input value: ~p", [Input]),
+            {ok, _} = application:ensure_all_started(looking_glass),
+            lg:trace(Input, lg_file_tracer, "traces.lz4", #{
+                mode => profile,
+                running => true,
+                send => true})
+    end.
+
+parse_value(Value) ->
+    [begin
+        [Mod, Fun] = string:tokens(C, ":"),
+        {callback, list_to_atom(Mod), list_to_atom(Fun)}
+    end || C <- string:tokens(Value, ",")].
+
+connections() ->
+    Pids = [Pid || {{conns_sup, _}, Pid} <- ets:tab2list(ranch_server)],
+    [{app, rabbit}, {app, rabbit_common}, {scope, Pids}].