rename default tracer and move setup to before root sup

src/opentelemetry.app.src

@@ -8,8 +8,8 @@
     stdlib,
     wts
    ]},
-  {env, [{tracer, #{span => {ot_span_ets, []},
-                    ctx => {ot_ctx_pdict, []}}}]},
+  {env, [{tracer, {ot_tracer_default, #{span => {ot_span_ets, []},
+                                        ctx => {ot_ctx_pdict, []}}}}]},
   {modules, []},
 
   {licenses, ["Apache 2.0"]},

src/opentelemetry_app.erl

@@ -23,14 +23,13 @@
 
 start(_StartType, _StartArgs) ->
     Opts = application:get_all_env(opentelemetry),
-    {ok, Pid} = opentelemetry_sup:start_link(Opts),
 
     %% if the span impl needs to have a process supervised it must be
     %% setup after the supervision tree has started.
-    {tracer, TracerOpts} = lists:keyfind(tracer, 1, Opts),
-    ot_tracer_sdk:setup(TracerOpts),
+    {tracer, {Tracer, TracerOpts}} = lists:keyfind(tracer, 1, Opts),
+    Children = ot_tracer:setup(Tracer, TracerOpts),
 
-    {ok, Pid}.
+    opentelemetry_sup:start_link(Children, Opts).
 
 stop(_State) ->
     ok.

src/opentelemetry_sup.erl

@@ -19,22 +19,22 @@
 
 -behaviour(supervisor).
 
--export([start_link/1]).
+-export([start_link/2]).
 
 -export([init/1]).
 
 -define(SERVER, ?MODULE).
 
-start_link(Opts) ->
-    supervisor:start_link({local, ?SERVER}, ?MODULE, [Opts]).
+start_link(Children, Opts) ->
+    supervisor:start_link({local, ?SERVER}, ?MODULE, [Children, Opts]).
 
-init([Opts]) ->
+init([Children, Opts]) ->
     SupFlags = #{strategy => one_for_one,
                  intensity => 0,
                  period => 1},
     ChildSpecs = [#{id => ot_span_sup,
                     start => {ot_span_sup, start_link, [Opts]},
-                    type => supervisor}],
+                    type => supervisor} | Children],
     {ok, {SupFlags, ChildSpecs}}.
 
 %% internal functions

src/ot_span.erl

@@ -26,7 +26,6 @@
 
 -export_type([start_opts/0]).
 
--callback setup(map()) -> ok.
 -callback start_span(opentelemetry:span_name(), start_opts()) -> opentelemetry:span_ctx().
 -callback finish_span(opentelemetry:span_ctx()) -> ok.
 -callback get_ctx(opentelemetry:span()) -> opentelemetry:span_ctx().

src/ot_span_ets.erl

@@ -26,8 +26,7 @@
          handle_call/3,
          handle_cast/2]).
 
--export([setup/1,
-         start_span/2,
+-export([start_span/2,
          finish_span/1,
          get_ctx/1,
          is_recording_events/1,
@@ -44,11 +43,6 @@
 %% table to store active spans
 -define(SPAN_TAB, otel_span_table).
 
-setup(_Opts) ->
-    {ok, _} = ot_span_sup:start_child(#{id => ?MODULE,
-                                        start => {?MODULE, start_link, [[]]}}),
-    ok.
-
 start_link(Opts) ->
     gen_server:start_link(?MODULE, Opts, []).
 

src/ot_span_utils.erl

@@ -50,21 +50,21 @@ start_span(Name, Opts) ->
     %% TODO: support overriding the sampler
     _Sampler = maps:get(sampler, Opts, undefined),
 
-    new_span_(Name, Parent, Kind, Attributes, Links).
+    new_span(Name, Parent, Kind, Attributes, Links).
 
 %% if parent is undefined, first run sampler
-new_span_(Name, undefined, Kind, Attributes, Links) ->
+new_span(Name, undefined, Kind, Attributes, Links) ->
     TraceId = opentelemetry:generate_trace_id(),
     Span = #span_ctx{trace_id=TraceId,
                      trace_options=0},
     TraceOptions = update_trace_options(should_sample, Span),
-    new_span_(Name, Span#span_ctx{trace_options=TraceOptions}, Kind, Attributes, Links);
+    new_span(Name, Span#span_ctx{trace_options=TraceOptions}, Kind, Attributes, Links);
 %% if parent is remote, first run sampler
 %% new_span_(Name, Span=#span_ctx{}, Kind, Attributes) %% when RemoteParent =:= true
 %%                                              ->
 %%     TraceOptions = update_trace_options(should_sample, Span),
 %%     new_span_(Name, Span#span_ctx{trace_options=TraceOptions}, Kind, Attributes);
-new_span_(Name, Parent=#span_ctx{trace_id=TraceId,
+new_span(Name, Parent=#span_ctx{trace_id=TraceId,
                                  trace_options=TraceOptions,
                                  tracestate=Tracestate,
                                  span_id=ParentSpanId}, Kind, Attributes, Links)
@@ -80,7 +80,7 @@ new_span_(Name, Parent=#span_ctx{trace_id=TraceId,
                  attributes=Attributes,
                  links=Links},
     {Parent#span_ctx{span_id=SpanId}, Span};
-new_span_(_Name, Parent, _Kind, _, _) ->
+new_span(_Name, Parent, _Kind, _, _) ->
     SpanId = opentelemetry:generate_span_id(),
     %% since discarded by sampler, create no span
     {Parent#span_ctx{span_id=SpanId}, undefined}.

src/ot_tracer.erl

@@ -17,7 +17,8 @@
 %%%-------------------------------------------------------------------------
 -module(ot_tracer).
 
--export([start_span/1,
+-export([setup/2,
+         start_span/1,
          start_span/2,
          start_span/3,
          with_span/1,
@@ -29,7 +30,7 @@
 
 -include("opentelemetry.hrl").
 
--define(tracer, (persistent_term:get({opentelemetry, tracer}, ot_tracer_sdk))).
+-define(tracer, (persistent_term:get({?MODULE, tracer}))).
 -define(CURRENT_TRACER, {?MODULE, current_tracer}).
 
 -callback start_span(opentelemetry:span_name(), ot_span:start_opts()) -> opentelemetry:span_ctx().
@@ -40,6 +41,11 @@
 -callback get_binary_format() -> binary().
 -callback get_http_text_format() -> opentelemetry:http_headers().
 
+-spec setup(module(), map()) -> [supervisor:child_spec()].
+setup(Tracer, TracerOpts) ->
+    persistent_term:put({?MODULE, tracer}, Tracer),
+    Tracer:setup(TracerOpts).
+
 -spec start_span(opentelemetry:span_name()) -> opentelemetry:span_ctx().
 start_span(Name) ->
     start_span(Name, #{}).

src/ot_tracer_sdk.erl → src/ot_tracer_default.erl

@@ -15,7 +15,7 @@
 %% @doc
 %% @end
 %%%-------------------------------------------------------------------------
--module(ot_tracer_sdk).
+-module(ot_tracer_default).
 
 -behaviour(ot_tracer).
 
@@ -37,19 +37,20 @@
 
 -type pdict_trace_ctx() :: {opentelemetry:span_ctx(), pdict_trace_ctx() | undefined}.
 
+-spec setup(map()) -> [supervisor:child_spec()].
 setup(Opts) ->
-    setup_impl(ctx, ?CTX_IMPL_KEY, Opts),
-    setup_impl(span, ?SPAN_IMPL_KEY, Opts).
-
-setup_impl(ConfigKey, PersistentKey, Opts) ->
-    {Impl, Args} = maps:get(ConfigKey, Opts),
-    case erlang:function_exported(Impl, setup, 1) of
-        true ->
-            ok = Impl:setup(Args);
-        false ->
-            ok
-    end,
-    persistent_term:put(PersistentKey, Impl).
+    lists:filtermap(fun({ConfigKey, PersistentKey}) ->
+                        {Module, Args} = maps:get(ConfigKey, Opts),
+                        persistent_term:put(PersistentKey, Module),
+                        case erlang:function_exported(Module, start_link, 1) of
+                            true ->
+                                {true, #{id => Module,
+                                         start => {Module, start_link, [Args]}}};
+                            false ->
+                                false
+                        end
+                    end, [{ctx, ?CTX_IMPL_KEY},
+                          {span, ?SPAN_IMPL_KEY}]).
 
 -spec start_span(opentelemetry:span_name(), ot_span:start_opts()) -> opentelemetry:span_ctx().
 start_span(Name, Opts) ->