add baggage as span attributes

Author: Gustavo Aguiar

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)}.