From a5cbcf8c1189d84f5838e70624667dbe0161cef5 Mon Sep 17 00:00:00 2001
From: "Paul J. Davis" <paul.joseph.davis@gmail.com>
Date: Thu, 8 Mar 2018 11:00:33 -0600
Subject: WIP: Testing looking_glass for tracing

---
 rebar.config.script       |  7 ++++++-
 rel/reltool.config        |  8 ++++++--
 src/chttpd/src/chttpd.erl | 12 ++++++++++++
 3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/rebar.config.script b/rebar.config.script
index c33a71cb5..ed078f068 100644
--- a/rebar.config.script
+++ b/rebar.config.script
@@ -84,10 +84,15 @@ MakeDep = fun
         {AppName, ".*", {git, Url, Version}, Options}
 end,
 
+ExternalDeps = [
+    {lz4, ".*", {git, "https://github.com/rabbitmq/lz4-erlang", "master"}},
+    {looking_glass, ".*", {git, "https://github.com/rabbitmq/looking_glass.git", "master"}}
+],
+
 AddConfig = [
     {require_otp_vsn, "R16B03|R16B03-1|17|18|19|20"},
     {deps_dir, "src"},
-    {deps, lists:map(MakeDep, DepDescs)},
+    {deps, lists:map(MakeDep, DepDescs) ++ ExternalDeps},
     {sub_dirs, SubDirs},
     {lib_dirs, ["src"]},
     {erl_opts, [debug_info, {i, "../"}]},
diff --git a/rel/reltool.config b/rel/reltool.config
index 464f5f4fe..bef50ff12 100644
--- a/rel/reltool.config
+++ b/rel/reltool.config
@@ -55,7 +55,9 @@
         mochiweb,
         rexi,
         setup,
-        snappy
+        snappy,
+        lz4,
+        looking_glass
     ]},
     {rel, "start_clean", "", [kernel, stdlib]},
     {boot_rel, "couchdb"},
@@ -108,7 +110,9 @@
     {app, mochiweb, [{incl_cond, include}]},
     {app, rexi, [{incl_cond, include}]},
     {app, setup, [{incl_cond, include}]},
-    {app, snappy, [{incl_cond, include}]}
+    {app, snappy, [{incl_cond, include}]},
+    {app, lz4, [{incl_cond, include}]},
+    {app, looking_glass, [{incl_cond, include}]}
 ]}.
 
 {overlay_vars, "couchdb.config"}.
diff --git a/src/chttpd/src/chttpd.erl b/src/chttpd/src/chttpd.erl
index 6be0d1848..258449a79 100644
--- a/src/chttpd/src/chttpd.erl
+++ b/src/chttpd/src/chttpd.erl
@@ -142,8 +142,20 @@ stop() ->
 handle_request(MochiReq0) ->
     erlang:put(?REWRITE_COUNT, 0),
     MochiReq = couch_httpd_vhost:dispatch_host(MochiReq0),
+    maybe_trace(MochiReq),
     handle_request_int(MochiReq).
 
+
+maybe_trace(MochiReq) ->
+    case MochiReq:get_header_value("x-couchdb-trace") of
+        "true" ->
+            couch_log:info("Trace initializing...", []),
+            lg:trace(['_', {scope, [self()]}], lg_file_tracer, "traces.lz4", #{mode => profile});
+        _ ->
+            ok
+    end.
+
+
 handle_request_int(MochiReq) ->
     Begin = os:timestamp(),
     case config:get("chttpd", "socket_options") of
-- 
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