add baggage span processor

Author: gugahoa

processors/opentelemetry_baggage_processor/src/otel_baggage_processor.erl

@@ -2,6 +2,7 @@
 
 -behaviour(otel_span_processor).
 
+-include_lib("opentelemetry/include/otel_span.hrl").
 -include_lib("opentelemetry_api/include/opentelemetry.hrl").
 
 -export([
@@ -12,8 +13,10 @@
 -type processor_config() :: term().
 
 -spec on_start(otel_ctx:t(), opentelemetry:span(), processor_config()) -> opentelemetry:span().
-on_start(_Ctx, Span, _Config) ->
-  Span.
+on_start(Ctx, Span, _Config) ->
+  Baggage = otel_baggage:get_all(Ctx),
+  Attributes = maps:map(fun(_K, {Value, _Metadata}) -> Value end, Baggage),
+  add_attributes(Span, Attributes).
 
 -spec on_end(opentelemetry:span(), processor_config()) ->
           true | dropped | {error, invalid_span} | {error, no_export_buffer}.
@@ -23,3 +26,7 @@ on_end(_Span, _Config) ->
 -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)}.

processors/opentelemetry_baggage_processor/test/otel_baggage_processor_SUITE.erl

@@ -0,0 +1,56 @@
+-module(otel_baggage_processor_SUITE).
+
+-compile(export_all).
+
+-include_lib("common_test/include/ct.hrl").
+-include_lib("stdlib/include/assert.hrl").
+-include_lib("opentelemetry/include/otel_span.hrl").
+-include_lib("opentelemetry_api/include/otel_tracer.hrl").
+
+all() -> [
+          baggage_handling
+         ].
+
+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}}]),
+  Config.
+
+end_per_suite(_Config) ->
+  ok = application:unload(opentelemetry),
+  ok.
+
+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) ->
+  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">>),
+  ?end_span(),
+  ?set_current_span(SpanCtx2),
+  ?end_span(),
+  Attributes = get_span_attributes(<<"span-1">>),
+  ?assertEqual(Attributes, #{}),
+  Attributes2 = get_span_attributes(<<"span-2">>),
+  ?assertEqual(Attributes2, #{<<"key">> => <<"value">>}),
+  ok.
+
+get_span_attributes(Name) ->
+  receive
+    {span, #span{name=Name, attributes=Attributes}} ->
+      otel_attributes:map(Attributes)
+  after
+    100 ->
+      error(timeout)
+  end.