From 30af1111fea8a461fc3ee0203961ec6c566be419 Mon Sep 17 00:00:00 2001
From: Tristan Sloughter <t@crashfast.com>
Date: Mon, 6 Nov 2023 06:20:27 -0700
Subject: [PATCH] create unique processor name in otel_tracer_server

Each processor needs a unique name to reference but always creating
it in start_link means everytime the process restarts it creates
a new atom and new persistent term key. This is a leak. This patch
moves the atom creation to otel_tracer_server so it is only done once.
---
 apps/opentelemetry/src/otel_batch_processor.erl  | 16 +++++-----------
 apps/opentelemetry/src/otel_simple_processor.erl | 16 +++++-----------
 apps/opentelemetry/src/otel_tracer_server.erl    |  9 ++++++++-
 3 files changed, 18 insertions(+), 23 deletions(-)

diff --git a/apps/opentelemetry/src/otel_batch_processor.erl b/apps/opentelemetry/src/otel_batch_processor.erl
index d1374c55..433dea95 100644
--- a/apps/opentelemetry/src/otel_batch_processor.erl
+++ b/apps/opentelemetry/src/otel_batch_processor.erl
@@ -90,17 +90,11 @@ current_tab_to_list(RegName) ->
     ets:tab2list(?CURRENT_TABLE(RegName)).
 -endif.
 
-start_link(Config) ->
-    Name = case maps:find(name, Config) of
-               {ok, N} ->
-                   N;
-               error ->
-                   %% use a unique reference to distiguish multiple batch processors while
-                   %% still having a single name, instead of a possibly changing pid, to
-                   %% communicate with the processor
-                   erlang:ref_to_list(erlang:make_ref())
-           end,
-
+%% require a unique name to distiguish multiple batch processors while
+%% still having a single name, instead of a possibly changing pid, to
+%% communicate with the processor
+-spec start_link(#{name := atom() | list()}) -> {ok, pid(), map()}.
+start_link(Config=#{name := Name}) ->
     RegisterName = ?REG_NAME(Name),
     Config1 = Config#{reg_name => RegisterName},
     {ok, Pid} = gen_statem:start_link({local, RegisterName}, ?MODULE, [Config1], []),
diff --git a/apps/opentelemetry/src/otel_simple_processor.erl b/apps/opentelemetry/src/otel_simple_processor.erl
index eaa5fd83..bb877c4b 100644
--- a/apps/opentelemetry/src/otel_simple_processor.erl
+++ b/apps/opentelemetry/src/otel_simple_processor.erl
@@ -64,17 +64,11 @@
 -define(DEFAULT_EXPORTER_TIMEOUT_MS, timer:minutes(5)).
 -define(NAME_TO_ATOM(Name, Unique), list_to_atom(lists:concat([Name, "_", Unique]))).
 
-start_link(Config) ->
-    Name = case maps:find(name, Config) of
-               {ok, N} ->
-                   N;
-               error ->
-                   %% use a unique reference to distiguish multiple batch processors while
-                   %% still having a single name, instead of a possibly changing pid, to
-                   %% communicate with the processor
-                   erlang:ref_to_list(erlang:make_ref())
-           end,
-
+%% require a unique name to distiguish multiple simple processors while
+%% still having a single name, instead of a possibly changing pid, to
+%% communicate with the processor
+-spec start_link(#{name := atom() | list()}) -> {ok, pid(), map()}.
+start_link(Config=#{name := Name}) ->
     RegisterName = ?NAME_TO_ATOM(?MODULE, Name),
     Config1 = Config#{reg_name => RegisterName},
     {ok, Pid} = gen_statem:start_link({local, RegisterName}, ?MODULE, [Config1], []),
diff --git a/apps/opentelemetry/src/otel_tracer_server.erl b/apps/opentelemetry/src/otel_tracer_server.erl
index 4b536906..00e367e5 100644
--- a/apps/opentelemetry/src/otel_tracer_server.erl
+++ b/apps/opentelemetry/src/otel_tracer_server.erl
@@ -159,7 +159,14 @@ init_processor(SpanProcessorSup, ProcessorModule, Config) ->
     %% start_link is an optional callback for processors
     case lists:member({start_link, 1}, ProcessorModule:module_info(exports)) of
         true ->
-            try supervisor:start_child(SpanProcessorSup, [ProcessorModule, Config]) of
+            try supervisor:start_child(SpanProcessorSup,
+                                       [ProcessorModule,
+                                        %% use a unique reference to distiguish multiple processors of the same type while
+                                        %% still having a single name, instead of a possibly changing pid, to
+                                        %% communicate with the processor
+                                        maps:merge(#{name => erlang:ref_to_list(erlang:make_ref())},
+                                                   Config)])
+            of
                 {ok, _Pid, Config1} ->
                     {true, {ProcessorModule, Config1}};
                 {error, Reason} ->