add Elixir modules for baggage and context

apps/opentelemetry/test/opentelemetry_SUITE.erl

@@ -233,7 +233,7 @@ propagation(Config) ->
     ?assertEqual(undefined, ?current_span_ctx),
 
     %% clear our baggage from the context to test extraction
-    otel_ctx:remove(otel_baggage:ctx_key()),
+    otel_baggage:clear(),
     ?assertEqual(#{}, otel_baggage:get_all()),
 
     %% make header keys uppercase to validate the extractor is case insensitive

apps/opentelemetry_api/lib/open_telemetry/baggage.ex

@@ -0,0 +1,13 @@
+defmodule OpenTelemetry.Baggage do
+  @moduledoc """
+  Baggage is used to annotate telemetry, adding context and information to
+  metrics, traces, and logs. It is represented by a set of name/value pairs
+  describing user-defined properties.
+  """
+
+  defdelegate set(keyvalues), to: :otel_baggage
+  defdelegate set(key, values), to: :otel_baggage
+  defdelegate get_all(), to: :otel_baggage
+  defdelegate clear(), to: :otel_baggage
+  defdelegate get_text_map_propagators(), to: :otel_baggage
+end

apps/opentelemetry_api/lib/open_telemetry/ctx.ex

@@ -0,0 +1,18 @@
+defmodule OpenTelemetry.Ctx do
+  @moduledoc """
+  Ctx is responsible for propagating values within a process that are associated
+  with a particular Trace or set of Baggage. `OpenTelemetry.Tracer` and
+  `OpenTelemetry.Baggage` handle updating the Context.
+  """
+
+  defdelegate new(), to: :otel_ctx
+  defdelegate attach(ctx), to: :otel_ctx
+  defdelegate detach(token), to: :otel_ctx
+  defdelegate set_value(key, value), to: :otel_ctx
+  defdelegate set_value(ctx, key, value), to: :otel_ctx
+  defdelegate get_value(key, default), to: :otel_ctx
+  defdelegate get_value(ctx, key, default), to: :otel_ctx
+  defdelegate clear(), to: :otel_ctx
+  defdelegate remove(key), to: :otel_ctx
+  defdelegate get_current(), to: :otel_ctx
+end

apps/opentelemetry_api/src/otel_baggage.erl

@@ -12,14 +12,17 @@
 %% See the License for the specific language governing permissions and
 %% limitations under the License.
 %%
-%% @doc
+%% @doc Baggage is used to annotate telemetry, adding context and
+%% information to metrics, traces, and logs. It is represented by a set
+%% of name/value pairs describing user-defined properties.
 %% @end
 %%%-------------------------------------------------------------------------
 -module(otel_baggage).
 
--export([ctx_key/0,
+-export([set/1,
          set/2,
          get_all/0,
+         clear/0,
          get_text_map_propagators/0]).
 
 -type key() :: string().
@@ -34,8 +37,12 @@
 -define(BAGGAGE_KEY, '$__otel_baggage_ctx_key').
 -define(BAGGAGE_HEADER, <<"baggage">>).
 
-ctx_key() ->
-    ?BAGGAGE_KEY.
+-spec set(#{key() => value()} | [{key(), value()}]) -> ok.
+set(KeyValues) when is_list(KeyValues) ->
+    set(maps:from_list(KeyValues));
+set(KeyValues) when is_map(KeyValues) ->
+    Baggage = otel_ctx:get_value(?BAGGAGE_KEY, #{}),
+    otel_ctx:set_value(?BAGGAGE_KEY, maps:merge(Baggage, KeyValues)).
 
 -spec set(key(), value()) -> ok.
 set(Key, Value) ->
@@ -46,6 +53,10 @@ set(Key, Value) ->
 get_all() ->
     otel_ctx:get_value(?BAGGAGE_KEY, #{}).
 
+-spec clear() -> ok.
+clear() ->
+    otel_ctx:set_value(?BAGGAGE_KEY, #{}).
+
 -spec get_text_map_propagators() -> {otel_propagator:text_map_extractor(), otel_propagator:text_map_injector()}.
 get_text_map_propagators() ->
     ToText = fun(Baggage) when is_map(Baggage) ->

apps/opentelemetry_api/src/otel_ctx.erl

@@ -12,7 +12,10 @@
 %% See the License for the specific language governing permissions and
 %% limitations under the License.
 %%
-%% @doc
+%% @doc Ctx is responsible for propagating values within a process that
+%% are associated with a particular Trace or set of Baggage.
+%% `OpenTelemetry.Tracer` and `OpenTelemetry.Baggage` handle updating
+%% the Context.
 %% @end
 %%%-------------------------------------------------------------------------
 -module(otel_ctx).

apps/opentelemetry_api/test/open_telemetry_test.exs

@@ -3,6 +3,8 @@ defmodule OpenTelemetryTest do
 
   require OpenTelemetry.Tracer, as: Tracer
   require OpenTelemetry.Span, as: Span
+  require OpenTelemetry.Baggage, as: Baggage
+  require OpenTelemetry.Ctx, as: Ctx
 
   require Record
   @fields Record.extract(:span_ctx, from_lib: "opentelemetry_api/include/opentelemetry.hrl")
@@ -63,4 +65,42 @@ defmodule OpenTelemetryTest do
       assert []   = Span.tracestate(span)
     end
   end
+
+  test "baggage api from elixir" do
+    Baggage.set(%{"a" => "b"})
+    assert %{"a" => "b"} = Baggage.get_all()
+
+    Baggage.set(%{"a" => "c"})
+    assert %{"a" => "c"} = Baggage.get_all()
+
+    Baggage.clear()
+    assert 0 = :erlang.map_size(Baggage.get_all())
+  end
+
+  test "context api from elixir" do
+    ctx = Ctx.new()
+    ctx = Ctx.set_value(ctx, :somekey, :somevalue)
+    assert :somevalue = Ctx.get_value(ctx, :somekey, "default")
+
+    # attach the context and get value from implicit attached context
+    Ctx.attach(ctx)
+    assert :somevalue = Ctx.get_value(:somekey, "default")
+  end
+
+  test "baggage across contexts" do
+    ctx = Ctx.get_current()
+
+    Baggage.set(%{"a" => "b"})
+    assert %{"a" => "b"} = Baggage.get_all()
+
+    # attach the empty context
+    # gets a token for the context
+    token = Ctx.attach(ctx)
+    assert 0 = :erlang.map_size(Baggage.get_all())
+
+    # return to the context in the pdict before the attach
+    Ctx.detach(token)
+    assert %{"a" => "b"} = Baggage.get_all()
+  end
+
 end