add filter and prefix configuration

Author: gugahoa

processors/opentelemetry_baggage_processor/lib/opentelemetry_baggage_processor.ex

@@ -1,7 +1,8 @@
 defmodule OpentelemetryBaggageProcessor do
-  @moduledoc """
-  TODO: Add something here
-  """
+  @external_resource readme = Path.join([__DIR__, "../README.md"])
 
-  # TODO: Create an add_attribute_to_trace or something like that
+  @moduledoc readme
+             |> File.read!()
+             |> String.split("<!-- MDOC -->")
+             |> Enum.fetch!(1)
 end

processors/opentelemetry_baggage_processor/src/otel_baggage_processor.erl

@@ -5,28 +5,61 @@
 -include_lib("opentelemetry/include/otel_span.hrl").
 -include_lib("opentelemetry_api/include/opentelemetry.hrl").
 
--export([
-         on_start/3,
-         on_end/2,
-         force_flush/1]).
+-export([on_start/3, on_end/2, force_flush/1]).
 
 -type processor_config() :: term().
 
--spec on_start(otel_ctx:t(), opentelemetry:span(), processor_config()) -> opentelemetry:span().
-on_start(Ctx, Span, _Config) ->
+-spec on_start(otel_ctx:t(), opentelemetry:span(), processor_config()) ->
+                opentelemetry:span().
+on_start(Ctx, Span, Config) ->
   Baggage = otel_baggage:get_all(Ctx),
-  Attributes = maps:map(fun(_K, {Value, _Metadata}) -> Value end, Baggage),
+  Attributes =
+    maps:fold(fun(Key, {Value, Metadata}, Attributes) ->
+                 NewKey = add_prefix(Key, Config),
+                 case filter(Metadata, Config) of
+                   false -> Attributes;
+                   true -> [{NewKey, Value}] ++ Attributes
+                 end
+              end,
+              [],
+              Baggage),
   add_attributes(Span, Attributes).
 
 -spec on_end(opentelemetry:span(), processor_config()) ->
-          true | dropped | {error, invalid_span} | {error, no_export_buffer}.
+              true | dropped | {error, invalid_span} | {error, no_export_buffer}.
 on_end(_Span, _Config) ->
   true.
 
 -spec force_flush(processor_config()) -> ok | {error, term()}.
 force_flush(_Config) ->
   ok.
 
--spec add_attributes(opentelemetry:span(), opentelemetry:attributes_map()) -> opentelemetry:span().
-add_attributes(Span = #span{attributes=SpanAttributes}, AttributesMap) ->
-  Span#span{attributes=otel_attributes:set(AttributesMap, SpanAttributes)}.
+-spec add_attributes(opentelemetry:span(), opentelemetry:attributes_map()) ->
+                      opentelemetry:span().
+add_attributes(Span = #span{attributes = SpanAttributes}, AttributesMap) ->
+  Span#span{attributes = otel_attributes:set(AttributesMap, SpanAttributes)}.
+
+-spec filter(otel_baggage:metadata(), map()) -> boolean().
+filter(Metadata, #{filter := FilterKey}) ->
+  case lists:search(fun (Key) when Key == FilterKey ->
+                         true;
+                       (_) ->
+                         false
+                   end,
+                   Metadata) of
+    false ->
+      false;
+    {value, _} ->
+      true
+  end;
+filter(_Metadata, _Config) ->
+  true.
+
+-spec add_prefix(opentelemetry:attribute_key(), map()) -> opentelemetry:attribute_key().
+add_prefix(Key, #{prefix := Prefix}) when is_binary(Key), is_binary(Prefix) ->
+  <<Prefix/binary, Key/binary>>;
+add_prefix(Key, #{prefix := Prefix}) when is_atom(Key), is_binary(Prefix) ->
+  Key2 = atom_to_binary(Key),
+  <<Prefix/binary, Key2/binary>>;
+add_prefix(Key, _Config) ->
+  Key.

processors/opentelemetry_baggage_processor/test/otel_baggage_processor_SUITE.erl

@@ -6,14 +6,16 @@
 -include_lib("opentelemetry/include/otel_span.hrl").
 -include_lib("opentelemetry_api/include/otel_tracer.hrl").
 
-all() -> [
-          baggage_handling
-         ].
+all() ->
+  [baggage_handling, add_prefix_to_attributes, filter_baggage_attributes].
 
 init_per_suite(Config) ->
   ok = application:load(opentelemetry_baggage_processor),
   ok = application:load(opentelemetry),
-  application:set_env(opentelemetry, processors, [{otel_baggage_processor, #{}}, {otel_batch_processor, #{scheduled_delay_ms => 1}}]),
+  application:set_env(opentelemetry,
+                      processors,
+                      [{otel_baggage_processor, #{}},
+                       {otel_batch_processor, #{scheduled_delay_ms => 1}}]),
   Config.
 
 end_per_suite(_Config) ->
@@ -22,20 +24,22 @@ end_per_suite(_Config) ->
 
 init_per_testcase(_, Config) ->
   {ok, _} = application:ensure_all_started(opentelemetry_baggage_processor),
-  otel_batch_processor:set_exporter(otel_exporter_pid, self()),
   Config.
 
 end_per_testcase(_, Config) ->
   application:stop(opentelemetry),
   Config.
 
 baggage_handling(_Config) ->
+  {ok, _} = application:ensure_all_started(opentelemetry),
+  otel_batch_processor:set_exporter(otel_exporter_pid, self()),
   SpanCtx1 = ?start_span(<<"span-1">>),
   ?set_current_span(SpanCtx1),
   Ctx = otel_ctx:get_current(),
   Ctx2 = otel_baggage:set(Ctx, <<"key">>, <<"value">>),
   _Token = otel_ctx:attach(Ctx2),
-  SpanCtx2 = ?start_span(<<"span-2">>, #{attributes => #{<<"existing-attribute">> => true}}),
+  SpanCtx2 =
+    ?start_span(<<"span-2">>, #{attributes => #{<<"existing-attribute">> => true}}),
   ?end_span(),
   ?set_current_span(SpanCtx2),
   ?end_span(),
@@ -45,11 +49,47 @@ baggage_handling(_Config) ->
   ?assertEqual(Attributes2, #{<<"key">> => <<"value">>, <<"existing-attribute">> => true}),
   ok.
 
+add_prefix_to_attributes(_Config) ->
+  application:set_env(opentelemetry,
+                      processors,
+                      [{otel_baggage_processor, #{prefix => <<"app.">>}},
+                       {otel_batch_processor, #{scheduled_delay_ms => 1}}]),
+  {ok, _} = application:ensure_all_started(opentelemetry),
+  otel_batch_processor:set_exporter(otel_exporter_pid, self()),
+  Ctx = otel_ctx:get_current(),
+  Ctx2 = otel_baggage:set(Ctx, <<"key">>, <<"value">>),
+  Ctx3 = otel_baggage:set(Ctx2, atom_key, <<"value">>),
+  _Token = otel_ctx:attach(Ctx3),
+  SpanCtx1 = ?start_span(<<"span-1">>),
+  ?set_current_span(SpanCtx1),
+  ?end_span(),
+  Attributes = get_span_attributes(<<"span-1">>),
+  ?assertEqual(#{<<"app.key">> => <<"value">>, <<"app.atom_key">> => <<"value">>},
+               Attributes),
+  ok.
+
+filter_baggage_attributes(_Config) ->
+  application:set_env(opentelemetry,
+                      processors,
+                      [{otel_baggage_processor, #{filter => <<"trace_field">>}},
+                       {otel_batch_processor, #{scheduled_delay_ms => 1}}]),
+  {ok, _} = application:ensure_all_started(opentelemetry),
+  otel_batch_processor:set_exporter(otel_exporter_pid, self()),
+  Ctx = otel_ctx:get_current(),
+  Ctx2 = otel_baggage:set(Ctx, <<"key">>, <<"value">>),
+  Ctx3 = otel_baggage:set(Ctx2, atom_key, <<"value">>, [<<"trace_field">>]),
+  _Token = otel_ctx:attach(Ctx3),
+  SpanCtx1 = ?start_span(<<"span-1">>),
+  ?set_current_span(SpanCtx1),
+  ?end_span(),
+  Attributes = get_span_attributes(<<"span-1">>),
+  ?assertEqual(#{<<"atom_key">> => <<"value">>}, Attributes),
+  ok.
+
 get_span_attributes(Name) ->
   receive
-    {span, #span{name=Name, attributes=Attributes}} ->
+    {span, #span{name = Name, attributes = Attributes}} ->
       otel_attributes:map(Attributes)
-  after
-    100 ->
-      error(timeout)
+  after 100 ->
+    error(timeout)
   end.